JP6064474B2 - Control device for synchronous motor - Google Patents

Description

  The present invention relates to a drive control technique for a synchronous motor, and more particularly to a technique for driving and controlling a synchronous motor so that a desired output can be obtained with certainty.

  Permanent magnet synchronous motor having a permanent magnet in the rotor, winding rotary field type synchronous motor having a field winding in the rotor, a synchronous reluctance motor in which the rotor is constituted by a ferromagnetic iron core, etc. Vector control for variable speed driving of “synchronous motors” (sometimes collectively referred to as “synchronous motors”) is realized in the following manner. First, the position of the rotor (more precisely, the position of the magnetic pole in the rotor) is detected using a sensor such as an encoder. Then, the d axis (coordinate axis in the direction of the central axis of the magnetic pole in vector control) is determined in the direction of the N pole in the rotor, the q axis is determined in a direction advanced by π / 2 from this, and the d axis corresponding to the desired torque The magnitude and phase of the voltage applied to the synchronous motor are adjusted so that the current and the q-axis current flow. In this way, vector control is realized. In recent years, a sensorless drive control system that estimates the position of the rotor based on the voltage and current supplied from the inverter to the synchronous motor without using a sensor such as an encoder has been proposed.

  In the vector control, the actual rotor position in the synchronous motor and the rotor position detected by the sensor (or the rotor position estimated based on the voltage and current supplied from the inverter to the synchronous motor). If there is a difference, there arises a problem that a desired torque cannot be obtained even if a current corresponding to the torque command value flows to the synchronous motor. For this reason, various techniques for accurately detecting (or estimating) the position of the rotor of the synchronous motor have been proposed, and the technique disclosed in Patent Document 1 can be cited as an example.

  Patent Document 1 discloses a technology that makes it possible to estimate an initial position of a rotor accurately and in a short time in a sensorless drive control system that uses an embedded magnet type synchronous motor as a target of drive control. ing. The embedded magnet type synchronous motor is a salient pole type synchronous motor in which the d-axis inductance Ld is smaller than the q-axis inductance Lq (that is, Ld <Lq), and has the property that the inductance in the d-axis direction is minimized. Yes. In the technique disclosed in Patent Document 1, the initial position of the rotor is estimated using this property. Specifically, in the technique disclosed in Patent Document 1, a predetermined voltage is applied to the synchronous motor to be driven and controlled over an electrical angle of 0 to 360 degrees, and as a result, the inductance is calculated from the current flowing through the synchronous motor. The position where the inductance is minimized is defined as the d-axis position (that is, the position of the N pole in the rotor).

JP 2001-78486 A

  Since the technique disclosed in Patent Document 1 uses the characteristics of a salient pole type synchronous motor for estimating the position of the rotor, the salient pole ratio of a surface magnet type synchronous motor is 1 (that is, Ld = Lq). It is not applicable to the drive control of a non-salient type synchronous motor.

  The present invention has been made in view of the above problems, and is intended to drive and control a synchronous motor so as to reliably obtain a desired output regardless of whether it is a salient pole type or a non-salient pole type. The aim is to provide technology that makes it possible.

  In order to solve the above-described problems, the present invention functions as follows: a control device that drives and controls a synchronous motor (more precisely, a control device that controls an inverter that supplies AC power to the synchronous motor). Current calculating means, adjusting means, and current feedback means. The current calculation means includes a d-axis current command value that specifies a d-axis current value and a q-axis current value that specifies a current value of a q-axis current based on a torque command value that specifies a torque to be output to a synchronous motor that is subject to drive control. Calculate the current command value. The adjusting means sets the detected value of the synchronous motor torque to an offset for making the position indicated by the rotor position information indicating the estimated value or detected value of the rotor position of the synchronous motor coincide with the actual rotor position in the synchronous motor. The rotational position information is adjusted based on the offset, and output to the current feedback means. More specifically, the adjusting means detects the torque while controlling the current calculating means so that the q-axis current command value becomes zero and a d-axis current command value having a predetermined value other than zero is output. The offset is determined so that the value becomes zero. The current feedback means converts the DC power into AC power by switching and supplies a gate signal for controlling switching in the inverter supplied to the synchronous motor from the d-axis current command value, the q-axis current command value, and the inverter. It is generated based on the detected value of the current supplied to the synchronous motor and the rotor position information that has been adjusted by the adjusting means, and is supplied to the inverter.

  The greatest technical feature of the present invention is that the adjusting means is provided. The position of the rotor indicated by the rotor position information that has undergone the offset adjustment by this adjusting means coincides with the actual position of the rotor in the synchronous motor to be driven. The reason why both match will be clarified in the description of the embodiment of the present invention.

  It should be noted that in the present invention, the characteristics of the salient pole type synchronous motor (that is, the d-axis inductance Ld is smaller than the q-axis inductance Lq) are used when adjusting the rotor position information. In addition, the property of the nonsalient pole type synchronous motor (that is, the salient pole ratio is 1) is not utilized. Therefore, according to the present invention, it is possible to adjust the rotor position information so that it matches the actual rotor position regardless of whether it is a salient pole type or a non-salient pole type. It is possible to reliably obtain the output of.

It is a figure which shows the structural example of the drive control system 1 of the electric motor containing the control apparatus 20 of embodiment of this invention. It is a figure for demonstrating the specific execution aspect of the rotor position information adjustment procedure in this embodiment. It is a figure which shows an example of the position which the actual rotor position of the motor M1 and a rotor position information show. It is a figure which shows an example of the position which the actual rotor position of the motor M1 and a rotor position information show. It is an example of a voltage vector diagram when only a positive d-axis current is passed. It is an example of a voltage vector diagram when only a negative d-axis current is passed.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a diagram illustrating a configuration example of a drive control system 1 for an electric motor including a control device 20 according to an embodiment of the present invention. This drive control system 1 is for performing drive control of a permanent magnet embedded synchronous motor. In FIG. 1, an electric motor M <b> 1 that is a permanent magnet embedded synchronous motor that is driven and controlled by the drive control system 1 is also illustrated along with the drive control system 1. As shown in FIG. 1, the drive control system 1 includes an inverter 10, a control device 20, a rotor position detection unit 30, and a torque detection unit 40.

The inverter 10 is, for example, a PWM (Pulse Width
Modulation) An inverter that converts DC power supplied from a DC power supply (not shown in FIG. 1) into three-phase AC power and supplies it to the motor M1. Although not shown in detail in FIG. 1, the inverter 10 has a switching element such as an IGBT (Insulated Gate Bipolar Transistor). In the inverter 10, the switching from the DC power to the AC power is realized by switching the switching element according to the gate signal given from the control device 20. The control device 20 is a device that generates the gate signal based on a torque command value T ^* that specifies the output torque of the electric motor M1. The specific configuration of the control device 20 will be clarified later. The rotor position detection means 30 is, for example, a resolver or an encoder, detects the position (rotation angle) of the rotor of the electric motor M1, and gives the rotor position information θ indicating the detected value to the control device 20. The torque detection means 40 detects the output torque of the electric motor M1 and gives the torque detection value Tdet to the control device 20. Among the components of the drive control system 1, the inverter 10, the rotor position detection means 30 and the torque detection means 40 are not particularly different from those in the conventional drive control system.
For this reason, below, it demonstrates focusing on the control apparatus 20. FIG.

Although the detailed illustration is omitted in FIG. 1, the control device 20 includes a CPU (Central Processing Unit) and an EEPROM (Electrically Erasable Programmable).
It is a computer device having a non-volatile storage unit such as a read-only memory and a volatile storage unit such as a RAM (Random Access Memory). A control program for causing the CPU to function as the current calculation unit 210, the adjustment unit 220, and the current feedback unit 230 in FIG. 1 is stored in advance in the nonvolatile storage unit of the control device 20. The CPU of the control device 20 functions as the current calculation unit 210, the adjustment unit 220, and the current feedback unit 230 in FIG. 1 by reading the control program stored in the nonvolatile storage unit into the volatile storage unit and executing it. To do. That is, the current calculation unit 210, the adjustment unit 220, and the current feedback unit 230 in FIG. 1 are all software modules. As described above, in the present embodiment, each of the current calculation unit 210, the adjustment unit 220, and the current feedback unit 230 is realized by software. However, these units are realized by an electronic circuit, and the control device 20 is configured. Is of course good.

As shown in FIG. 1, the current calculation means 210 is given a torque command value T ^* that specifies the output torque of the electric motor M1. The current calculation means 210 uses a torque command value as a d-axis current command value id ^* for controlling the d-axis current flowing to the motor M1 and a q-axis current command value iq ^* for controlling the q-axis current flowing to the motor M1. Calculation is performed based on T ^* and provided to the current feedback means 230. As is well known, the torque T of the electric motor M1, which is an embedded permanent magnet synchronous motor, is determined according to the current value iq of the q-axis current and the current value id of the d-axis current, as shown in (Equation 1). It is. In Equation (1), Pn is the number of pole pairs, Ψm is an armature flux linkage by a permanent magnet, Ld is a d-axis inductance, and Lq is a q-axis inductance. The first term on the right side of (Equation 1) is the torque generated by the magnetic flux generated by the permanent magnet, and the second term is the reluctance torque.
T = Pn. [Psi] m.iq + Pn. (Ld-Lq) .id.iq (1)

The adjustment means 220 is given rotor position information θ and a detected torque value Tdet. The adjusting means 220 determines an offset θof for adjusting the rotor position information θ so as to coincide with the actual rotor position in the electric motor M1, based on the torque detection value Tdet, and adjusts the offset θof (this embodiment) In the embodiment, the rotor position information θ is adjusted by subtracting the offset θof, or of course adding. Hereinafter, the rotor position information that has been adjusted by the adjusting means 220 will be referred to as “rotor position information θ ′”. Thus, the adjustment of the rotor position information θ is performed when there is a difference between the actual rotor position of the electric motor M1 and the rotor position indicated by the rotor position information θ in the torque command value T ^* . This is because the torque indicated by the torque command value T ^* cannot be obtained even if the corresponding current flows through the motor M1. The feature of this embodiment lies in the rotor position information adjustment processing executed by the adjustment means 220. Details of this rotor position information adjustment processing will be made later.

The current feedback means 230 uses a gate signal for controlling switching of a switching element included in the inverter 10 as a d-axis current command value id ^* , a q-axis current command value iq ^* , and a current supplied from the inverter 10 to the motor M1. Is generated based on the detected value (iu, iv) and the rotor position information θ ′ and supplied to the inverter 10. For example, when there is a margin in the output voltage of the inverter 10 with respect to the terminal voltage of the electric motor M1, the current feedback means 230 outputs a gate signal for switching the switching element so that the current flowing through the electric motor M1 is minimized. Conversely, when the latter is insufficient with respect to the former, a gate signal for switching the switching element is output so that field-weakening control is realized.
The above is the configuration of the control device 20.

Next, the rotor position information adjustment process in the adjustment unit 220 will be described.
As apparent from the above equation (1), the current value iq of the q-axis current is zero and the current value id of the d-axis current is a value other than zero (that is, only the d-axis current flows to the motor M1. In the state), the torque T becomes zero regardless of the magnitude relationship between Ld and Lq. The present invention focuses on this point and makes the actual rotor position in the motor M1 coincide with the rotor position in the control device 20 (that is, the position indicated by the rotor position information θ ′).

  FIG. 2 is a diagram for explaining a rotor position information adjustment procedure performed at the time of factory shipment of the drive control system 1 and the electric motor M1, for example. In FIG. 2, the same components as those in FIG. 1 are denoted by the same reference numerals. In FIG. 2, the combination of the drive control system 1 and the electric motor M1 is an adjustment target of the rotor position (magnetic pole position), and the rotor of the electric motor M1 passes through the shaft connecting means 60a, the torque detecting means 40, and the shaft connecting means 60b. And coupled to the rotor of the electric motor M2. The motor M2 is a permanent magnet embedded synchronous motor similar to the motor M1, and the inverter 50 is for driving the rotor of the motor M2 at a constant rotation. The rotor of the electric motor M1 is coupled to the rotor of the electric motor M2 through the shaft connecting means 60a, the torque detecting means 40 and the shaft connecting means 60b, and the rotor of the electric motor M2 is driven by the inverter 50 at a constant rotation. Therefore, the rotation of the rotor of the electric motor M1 is also a constant rotation.

For example, as shown in FIG. 3, when there is a difference between the actual rotor position of the electric motor M1 and the position indicated by the rotor position information θ, the adjustment of the rotor position information θ is performed as follows. First, the electric motor M2 is driven at a constant rotation by the inverter 50. In this state, the adjustment means 220 sets an initial value (for example, 0) to the offset θof to be subtracted from the rotor position information θ given from the rotor position detection means 30, and the q-axis current command value iq ^* is zero. The current calculation means 210 is controlled so that the d-axis current command value id ^* becomes a predetermined value other than zero. Next, the adjusting unit 220 repeatedly executes a process of increasing the offset θof by a predetermined amount and a process of giving the rotor position information θ obtained by subtracting the offset θof to the current feedback unit 230 until the detected torque value Tdet becomes zero. To do. By subtracting the offset θof determined in this way from the rotor position information θ, as shown in FIG. 3, the position indicated by the adjusted rotor position information (that is, the rotor position information θ ′) and the motor M1 This is because the difference θer from the actual rotor position can be made smaller than before the adjustment. Then, the adjusting unit 220 uses a nonvolatile storage unit as an offset for making the position indicated by the rotor position information θ the position indicated by the rotor position information θ coincide with the actual position of the rotor in the electric motor M1 when the torque detection value Tdet becomes zero. Write to.

Next, the adjusting means 220 is configured so that the positions of the N pole and the S pole in the electric motor M1 and the N pole and the S pole indicated by the rotor position information θ after adjustment (subtraction in this embodiment) for the offset θof is performed. It is determined whether or not the positions of the two positions are interchanged (that is, whether the positions of the two positions are shifted by π). This is because, in a permanent magnet type synchronous motor or a wound rotary field type synchronous motor, the q-axis current command value iq ^* is zero even when θer after adjustment is π as shown in FIG. This is because the torque detection value Tdet becomes zero when the d-axis current command value id ^* is a predetermined value other than zero.

If the induced voltage of the synchronous motor is Vme, the terminal voltage is Va, and the angular velocity is ω, the voltage vector diagrams when only the d-axis current flows are as shown in FIGS. More specifically, in FIG. 5, the positions of the N pole and the S pole in the electric motor M1 and the positions of the N pole and the S pole indicated by the rotor position information θ after subtracting the offset θof are the same. FIG. 6 is a voltage vector diagram when a negative d-axis current is passed under a situation, and FIG. 6 is a voltage vector diagram when a positive d-axis current is passed under the same situation. As is apparent from FIGS. 5 and 6, whether or not the terminal voltage is lower than the induced voltage when the negative d-axis current command value id ^* is given (in other words, the induced voltage is less than the terminal voltage). It can be determined whether or not the polarities are the same. This is utilized in the present embodiment. Specifically, the adjusting means 220 stores the rotor position information θ obtained by subtracting the offset θof after storing the offset θof when the torque detection value Tdet becomes zero in the non-volatile storage unit as described above. The current calculation means 210 is controlled so as to be supplied to the current feedback means 230 and to output a negative d-axis current command value id ^* . If the induced voltage increases from the terminal voltage, the adjusting unit 220 determines that the polarity is inverted, and rewrites the offset θof stored in the nonvolatile storage unit to a value that is smaller by π (may be a value that is larger by π).

  Thereafter, the adjusting unit 220 adjusts the rotor position information θ by subtracting the offset θof stored in the nonvolatile storage unit as described above, and provides the adjusted rotor position information θ ′ to the current feedback unit 230. For this reason, after the factory shipment of the drive control system 1 and the electric motor M1, the rotor position information is adjusted by the adjusting means 220 so as to coincide with the actual rotor position in the electric motor M1, and the adjusted rotor position information. Since the switching control of the inverter 10 is realized using the motor, it is possible to reliably output the torque according to the torque command value to the electric motor M1.

  It should be noted that in this embodiment, the characteristics of the salient pole type synchronous motor (that is, the d-axis inductance Ld is smaller than the q-axis inductance Lq) when adjusting the rotor position information are as follows. Of course, the property (Lq = Ld) of the non-salient electric motor is not used. For this reason, the control device 20 of the present embodiment can be applied not only to drive control of salient pole type synchronous motors but also to drive control of non salient pole type synchronous motors such as surface magnet type synchronous motors. . That is, according to the present embodiment, the synchronous motor is driven while adjusting the rotor position information so that it matches the actual rotor position regardless of whether it is a salient pole type or a non-salient pole type. Control can be performed, and a desired torque can be reliably output.

Although one embodiment of the present invention has been described above, it goes without saying that the following modifications may be added to this embodiment.
(1) In the above embodiment, the electric motor M1 that is driven and controlled by the control device 20 is a permanent magnet embedded type synchronous motor. However, the electric motor M1 may be a winding rotary field type synchronous motor, and may be synchronized. A type reluctance motor may be used. Even if the object of drive control is a winding rotary field type synchronous motor or synchronous type reluctance motor, by applying the present invention, the position of the rotor can be accurately estimated and a desired torque can be reliably obtained. This is because the drive can be controlled.

(2) In the above embodiment, a permanent magnet type synchronous motor is used as the motor M2 for controlling the rotation speed of the motor M1 to be constant. However, a wound rotary field type synchronous motor may be used as the motor M2. A synchronous reluctance motor may be used.

(3) In the above embodiment, θof is adjusted so that the detected torque value Tdet becomes zero in a state where only the d-axis current flows. However, the offset θof may be determined based on a plurality of types of detected torque values obtained by flowing d-axis currents having a plurality of types of current values through the motor M1 with the q-axis current set to zero. Specifically, it is conceivable that an offset with zero detected torque value is obtained for each of a plurality of types of d-axis currents by the same method as in the above embodiment, and an average value of these offsets is set as an offset θof. Further, θof may be determined so that the average value of the detected torque values detected when each of the plurality of types of d-axis currents flows is closest to zero.

(4) In the above embodiment, the inverter 10, the rotor position detection means 30, and the torque detection means 40 that constitute the drive control system 1 together with the control device 20 are hardware separate from the control device 20. However, of course, at least one of the inverter 10, the rotor position detection means 30, and the torque detection means 40 may be built in the control device 20.

(5) In the above embodiment, the position of the rotor of the electric motor M1 is detected by the rotor position detecting means 30 such as an encoder, and the rotor position information indicating the detected value is further adjusted by the adjusting means 220. However, it is also possible to apply the present invention to a sensorless control system that does not have the rotor position detecting means 30. This type of sensorless control system has rotor position estimation means for estimating the position of the rotor based on the current and voltage supplied from the inverter to the electric motor and outputting the estimated value as rotor position information. Therefore, the rotor position information output from the rotor position estimating means may be adjusted by the adjusting means 220.

(6) In the above embodiment, a control program that causes the CPU of the control device 20 to function as the current calculation unit 210, the adjustment unit 220, and the current feedback unit 230 is stored in advance in the nonvolatile storage unit of the control device 20. However, the control program may be distributed by being written on a computer-readable recording medium such as a CD-ROM, or may be distributed by downloading via a telecommunication line such as the Internet. This is because a control device that implements control of the inverter by software as in the above embodiment can function as the control device of the above embodiment by replacing existing software with the above control program. Further, in FIG. 2, when the present invention is applied to the adjustment of the rotor position information for the magnetic pole position of the electric motor M2, the torque calculation value of the inverter 50 is the target for adjusting the magnetic pole position instead of the torque detection value of the inverter 50. The motor 10 is fed back to the inverter 10 and the control device 20 connected to the motor M1, and the magnetic pole position is adjusted so that the torque calculation value of the inverter 50 becomes zero, so that the motor can be used without using the torque detector of the motor M1. It becomes possible to adjust the rotor position information of M1.

  DESCRIPTION OF SYMBOLS 1 ... Drive control system 10, 50 ... Inverter, 20 ... Control apparatus, 30 ... Rotor position detection means, 40 ... Torque detection means, 210 ... Current calculation means, 220 ... Adjustment means, 230 ... Current feedback means, M1, M2: Electric motor.

Claims (2)

Current calculating means for calculating a d-axis current command value and a q-axis current command value based on a torque command value for designating a torque to be output to a synchronous motor to be driven;
An offset for making the position indicated by the rotor position information indicating the estimated value or detected value of the rotor position of the synchronous motor coincide with the actual rotor position in the synchronous motor is used as the detected torque value of the synchronous motor. Adjusting means for determining and adjusting the offset position to the rotor position information;
A gate signal for controlling switching in an inverter that converts DC power into AC power by switching and supplies the synchronous motor to the synchronous motor is supplied to the d-axis current command value, the q-axis current command value, and the inverter to the synchronous motor. A current feedback means that is generated on the basis of the detected value of the supplied current and the rotor position information that has undergone adjustment by the adjustment means, and that is supplied to the inverter,
The adjusting means includes
The current calculation means is controlled so that zero is output as the q-axis current command value and non-zero is output as the d-axis current command value, so that the detected value of the torque of the synchronous motor becomes zero. after constant meta said offset, further adjusting the offset in accordance with the magnitude relationship between the terminal voltage and the induced voltage in the synchronous motor in the case where a negative d-axis current command value is output to the current calculation unit A control device for a synchronous motor as a feature. The said adjustment means determines the said offset based on the detected value of the torque of the said synchronous motor detected in each when a different d-axis current command value is made to output to the said current calculation means, The offset is characterized by the above-mentioned. The control apparatus according to 1.

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