JP2008148402A - Power conversion device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a power conversion device capable of automatically identifying moment of inertia. <P>SOLUTION: This power conversion device is made up of an inverter 1 which drives an electric motor 2, a control device 3 which gives a gate signal to power devices of the inverter 1, a current detection means 5 for the inverter 1, and a speed detection means 4. The control device 3 is provided with a speed model calculating section 30, which inputs a speed reference and calculates acceleration/deceleration torque reference and speed models; a speed control section 31, which inputs the speed models and a speed feedback signal, adds the acceleration/deceleration torque reference to its output, the prior-to-correction torque reference, and outputs a torque reference; a vector control or sensorless vector control means, which independently controls the currents of the excitation axis and torque axis of the electric motor 2, based on the torque reference and the current detected by current detection means 5; and a moment-of-inertia identification means 32, which automatically identifies the moment of inertial, used in the speed model calculation section 30 of the drive system of the electric motor 2. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a power conversion device for driving an electric motor.

  2. Description of the Related Art Conventionally, a power conversion device that drives an electric motor used in a process line or the like has adopted a configuration in which a DC voltage is converted into an alternating current by an inverter, and the electric motor is driven by this alternating current output to generate necessary speed and torque. . A speed sensor is connected to the motor, and the magnetic pole position or speed of the motor is detected. The speed feedback signal obtained from the speed sensor is compared with the given speed reference, and the deviation is PI (proportional integral) controlled by the speed controller, and the motor torque is controlled using this output as the torque reference or current reference. It was normal to make it so.

However, in the case where the load of the motor is oscillating and in the drive system where the control characteristics need to be increased, the above control system may be insufficient. As a countermeasure, a speed model calculation unit using the moment of inertia of the drive system is prepared in the control system, and the deviation between the speed model and the speed feedback signal is PI (proportional integration) to obtain a torque reference, A proposal has been made to suppress vibration by adding and correcting the torque reference output of the speed model to the torque reference (see, for example, Patent Document 1).
Japanese Patent Publication No. 5-40555 (Overall)

  The method disclosed in Patent Document 1 requires the moment of inertia of the drive system of the motor, that is, the sum of the moment of inertia of the mechanical system and the motor itself as an input condition. This moment of inertia is normally set as a fixed value. Therefore, once it is set, it is rarely changed. However, when the electric motor or the drive roll is replaced, resetting is required. Also, when the moment of inertia of the load changes due to secular change during operation, for example, surface wear of the drive roll, it is necessary to change the setting. Such a setting change is not only complicated, but there are cases where this setting is not performed despite the fact that the setting change is necessary due to the complexity.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a power conversion device capable of automatically identifying the moment of inertia.

  In order to achieve the above object, a power converter according to the present invention includes an inverter that converts a direct current into a desired alternating current to drive an electric motor, a control unit that supplies a gate signal to the power device of the inverter, and an output current of the inverter Current detecting means for detecting the speed of the motor and speed detecting means for detecting the speed of the motor directly or indirectly, and the control section receives a speed reference given from the outside as an input, and an acceleration / deceleration torque reference and a speed model The speed model calculation unit for calculating the speed, and the speed feedback signal obtained from the speed model and the speed detection means are input, and the torque reference for correction is added to the pre-correction torque reference that is the output to output the torque reference A speed control unit, and an excitation shaft current and a torque shaft current of the motor independently based on the torque reference and the current detected by the current detection means A vector control or sensorless vector control means Gosuru is characterized in that a moment of inertia identification means for automatically identifying the inertia moment of the driving system of the motor used in the velocity model calculation unit.

  According to the present invention, it is possible to provide a power converter that can automatically identify the moment of inertia.

  Embodiments of the present invention will be described below with reference to the drawings.

  Embodiment 1 of the present invention will be described below with reference to FIGS. Fig.1 (a) is a block block diagram of the power converter device which concerns on Example 1 of this invention.

  The inverter 1 receives a DC power supply, converts it into AC having a desired voltage and frequency, and drives the electric motor 2 with the output. The inverter 1 includes a main circuit in which power devices are bridge-connected, and each power device is ON / OFF controlled by a gate signal from the control unit 3. A speed detector 4 is attached to the electric motor 2, and this output is given to the control unit 3 as a speed feedback signal. Further, a current detector 5 is provided on the output side of the inverter 1, and this output is also given to the control unit 3 as a current feedback signal. Hereinafter, an internal configuration of the control unit 3 will be described.

  The speed reference given from the outside is given to the speed model calculator 30. The output of the speed model calculator 30 and the speed feedback signal described above are input to the speed controller 32. The speed controller 32 performs adjustment control so that the deviation between these signals is minimized, and provides the output to the vector controller 33 as a torque reference. The vector controller 33 converts the torque reference into a magnetic flux axis current reference and a torque axis current reference using a preset magnetic flux reference signal.

  The torque shaft current reference is compared with the torque feedback current obtained by converting the current feedback signal by the three-phase to two-phase converter 34, and the torque shaft current controller 35 is adjusted so that the deviation is minimized. Current control. Similarly, the magnetic flux axis current reference is compared with the magnetic flux feedback current obtained by converting the current feedback signal by the three-phase to two-phase converter 34 so that the deviation of the magnetic flux current controller 36 is minimized. Adjust current control. The outputs of the torque axis current controller 35 and the magnetic flux current controller 36 are the torque axis voltage reference and the flux axis voltage reference, respectively, which are input to the three-phase voltage reference generator 37, where the voltage reference for each phase is used as the voltage reference for each phase. The converted signal is supplied to the PWM circuit 38. The PWM circuit 38 modulates the voltage reference of each phase with a predetermined carrier signal and outputs a gate signal to be applied to the power device of the inverter 1.

  When the motor 2 is an induction motor, the slip frequency of the motor 2 is calculated by the slip calculator 39 from the torque axis current reference and the magnetic flux reference, and the inverter output frequency is obtained by adding the calculation result and the speed feedback signal. This is integrated by the integrator 40 to obtain the output phase reference of the inverter 1. This output phase reference becomes the conversion phase reference of the above-described three-phase to two-phase converter 34 and three-phase voltage reference generator 37. When the motor 2 is a synchronous motor, the slip frequency of the motor 2 is zero, so that the above slip frequency calculation can be omitted.

  The inertia moment J of the drive system is used as an internal constant of the speed model computing unit 30. In order to identify this inertia moment J, a J identifier 32 is provided.

  A detailed configuration of the speed model calculator 30, the speed controller 31, and the J identifier 32 is shown in FIG. The speed reference is given as an addition input to the PI controller 301 of the speed model calculator 30, and the output is multiplied by the stored value of the storage circuit 305 in which the reciprocal of the moment of inertia J of the drive system of the motor 2 is stored, and further integrated. Negative feedback is provided to the input of the PI controller 301 via the circuit 303. The output of the integration circuit 303 is a speed model signal, which is output via a switch 306 for selectively switching between the speed model signal and the speed reference. The output of the PI controller 301 becomes the acceleration / deceleration torque reference, and is output via the switch 306 configured to turn off the acceleration / deceleration torque reference.

  In the above configuration, the switching unit 306 is provided inside the speed model computing unit 30, but this may be provided inside the J identifier 32.

  Inside the speed controller 31, the speed feedback signal is subtracted from the speed model signal, and PI control is performed by the PI controller 311 so that this deviation is minimized. Then, the aforementioned acceleration / deceleration torque reference is added to the pre-correction torque reference that is the output of the PI controller 311, and as a result, a torque reference that is input to the vector controller 33 is obtained.

  The output of the PI controller 311 is subtracted from the output of the PI controller 301 and provided to the PI controller 304. The PI controller 304 can provide this output as the multiplication number of the multiplier 302 and can store this output in the storage circuit 305 as the reciprocal of the moment of inertia J. In this configuration, the PI controller 304 provided in the speed model calculator 30 may be provided in the J identifier 32.

  The effects of the above configuration will be described below with reference to FIGS.

  FIG. 2 is a flowchart showing an example of a procedure for identifying the moment of inertia J. First, in step ST1, the J identifier 32 selects the switch 306 as the measurement side. Thus, as described above, the speed-related input to the speed controller 31 is the speed reference itself, and the acceleration / deceleration torque reference correction signal is disconnected. Further, the output of the PI controller 304 becomes the multiplication number of the multiplier 302.

  In the above state, the speed reference is changed to a ramp shape, and operation is performed for a predetermined time at a predetermined acceleration rate (ST2). At this time, if the acceleration rate and the acceleration operation time are appropriately selected, in the closed loop control system on the speed model computing unit side, the output of the PI controller 304 is the acceleration / deceleration torque that is the output of the PI controller 301 as its input. Adjustment is made so that the deviation between the reference and the output of the PI controller 311 is minimized. When the multiplication number given to the multiplier 302 becomes the reciprocal of the inertia moment J of the drive system, the deviation is minimized, so the output of the PI controller 304 at this time is stored as the reciprocal of the inertia moment J. Store in the circuit 305 (ST3).

  This completes the identification of the moment of inertia. Next, the switch 306 is selected to the actual operation side (ST4). In this state, the speed reference is changed to a ramp shape and decelerated at a predetermined rate, for example. Then, it is confirmed that the speed deviation given from the speed controller 31 at that time is within a predetermined value (ST5). In step ST5, the number of multiplications given to the multiplier 302 is a value stored in the storage circuit 305. Therefore, if the stored value is surely the reciprocal of the inertia moment J of the drive system, the acceleration / deceleration torque is compensated at the time of actual operation acceleration / deceleration. If the acceleration / deceleration torque is properly compensated, the speed deviation is always within a predetermined value, and thus the moment of inertia J can be properly identified.

  FIG. 3 is a flowchart showing another example of the procedure for identifying the moment of inertia J.

  Also in the example shown in FIG. 3, the J identifier 32 selects the switch 306 on the measurement side (ST1), and changes the speed reference in a ramp shape (ST2). In this state, it is checked whether the speed deviation is equal to or less than a predetermined value (ST2A). In step ST2A, acceleration or deceleration operation is performed until the speed deviation becomes a predetermined value or less. When the speed deviation falls below a predetermined value, the output of the PI controller 304 is stored as the reciprocal of the moment of inertia J (ST3). Then, the identification of the moment of inertia is completed here, and the switch 306 is selected on the operation side to prepare for the actual operation (ST6).

  According to the identification method shown in FIG. 3, the confirmation procedure in step ST5 shown in FIG. 2 can be omitted.

  In the first embodiment of the present invention described above, the speed detector 4 is attached to the electric motor 2 as shown in FIG. 1 and so-called vector control is performed by the speed feedback signal of the speed detector 4. Even in the absence of the speed detector 4, it is possible to estimate the speed by calculation. In this case, it is obvious that so-called sensorless vector control can be performed.

  In Example 1, after the measurement for identifying the moment of inertia was performed, the reciprocal of the moment of inertia was stored in the memory circuit, and the stored value was used during actual operation. It is also possible to omit this memory circuit and always use the output of the PI controller which is the measuring circuit for identification as the reciprocal of the moment of inertia.

  In addition, the speed model calculator has a configuration in the normal case where the acceleration / deceleration torque due to the moment of inertia is dominant during acceleration / deceleration. However, depending on the application, the mechanical loss of the load may not be negligible. Therefore, in this case, a configuration in which a compensation element is added is adopted. In such a case, it is also possible to identify the inertial moment of the drive system using the average value of the inertial moment obtained during acceleration and the inertial moment obtained during deceleration.

  FIG. 4 is a detailed configuration diagram of a speed model calculator, a speed controller, and a J identifier of the power conversion device according to the second embodiment of the present invention. About each part of this Example 2, the same part as each part of the detailed block diagram of the speed model calculator, speed controller, and J identifier of the power converter according to Example 1 of FIG. The description is omitted. The second embodiment differs from the first embodiment in that the addition input of the PI controller 304 of the speed model computing unit 30A is a speed model signal and the subtraction input is a speed feedback signal.

  As shown in the second embodiment, it is obvious that the moment of inertia J can be identified by operating so that the speed model output of the speed model computing unit 30A coincides with the speed feedback instead of the torque reference base. It is. It is also clear that the identification method shown in FIGS. 2 and 3 of the first embodiment can be used in the velocity deviation-based inertia moment identification method of the second embodiment.

The block block diagram of the power converter device which concerns on Example 1 of this invention, and the detailed block diagram of a speed model calculating unit, a speed controller, and a J identifier. The flowchart which shows an example of the procedure for identifying the moment of inertia J. The flowchart which shows another example of the procedure for identifying the moment of inertia J. The detailed block diagram of the speed model calculator, speed controller, and J identifier in the power converter device which concerns on Example 2 of this invention.

Explanation of symbols

1 Inverter 2 Electric motor 3 Control unit 4 Speed sensor 5 Current detector

30, 30A Speed model calculator 31 Speed controller 32 J identifier 33 Vector calculator 34 Three-phase to two-phase current converter 35 Torque current controller 36 Magnetic flux current controller 37 Three-phase voltage reference converter 38 PWM control circuit 39 Slip calculator 40 integrator

301 PI Controller 302 Multiplier 303 Integrator 304, 304A PI Controller 306 Switch 311 PI Controller

Claims (7)

An inverter that drives a motor by converting direct current to desired alternating current;
A control unit for providing a gate signal to the power device of the inverter;
Current detection means for detecting an output current of the inverter;
A speed detecting means for directly or indirectly detecting the speed of the electric motor;
The controller is
A speed model calculation unit that calculates a speed reference and a speed reference for acceleration / deceleration using a speed reference given from the outside,
A speed control unit that receives a speed feedback signal obtained from the speed model and the speed detection means, and adds the acceleration / deceleration torque reference to an uncorrected torque reference that is an output thereof, and outputs a torque reference;
Vector control or sensorless vector control means for independently controlling the current of the excitation shaft and the torque shaft of the electric motor based on the torque reference and the current detected by the current detection means;
An electric power conversion apparatus comprising: an inertia moment identifying means for automatically identifying an inertia moment of a drive system of the electric motor used in the speed model calculation unit. The speed model calculation unit includes:
A first PI controller that takes a deviation between the speed reference and the speed model as an input and adjusts the acceleration / deceleration torque reference that is an output so as to minimize the deviation;
A multiplier for multiplying the output of the first PI controller by the reciprocal of the moment of inertia of the drive system of the motor; and an integrator for integrating the output of the multiplier to obtain the speed model. The power conversion device according to claim 1. The inertia moment identification means includes
At the time of measuring the moment of inertia, switching means for switching the input of the speed model to the speed control unit to the speed reference and turning off the addition correction of the acceleration / deceleration torque reference, the pre-correction torque reference, and the acceleration A second PI controller that receives the deviation of the deceleration torque reference,
The switching means is selected as the measurement side, and the reciprocal of the moment of inertia is replaced with the output of the second PI controller, and the motor is accelerated or decelerated for a predetermined time. At this time, the second PI controller The power converter according to claim 2, wherein the output is stored as a reciprocal of a new moment of inertia. The inertia moment identification means includes
When the moment of inertia is measured, the input of the speed model to the speed control unit is switched to the speed reference, and switching means for turning off the addition correction of the acceleration / deceleration torque reference, the speed model, and the speed feedback signal A third PI controller with the deviation as input,
The switching means is selected as the measurement side, and the reciprocal of the moment of inertia is replaced with the output of the third PI controller, and the motor is accelerated or decelerated for a predetermined time. At this time, the third PI controller The power converter according to claim 2, wherein the output is stored as a reciprocal of a new moment of inertia.   The measurement of the moment of inertia is completed when a deviation between the speed model and the speed feedback signal is equal to or less than a predetermined value when the motor is accelerated or decelerated by selecting the switching means as the driving side. The power conversion device according to claim 3 or 4, wherein the power conversion device is determined. The inertia moment identification means includes
At the time of measuring the moment of inertia, switching means for switching the input of the speed model to the speed control unit to the speed reference and turning off the addition correction of the acceleration / deceleration torque reference, the pre-correction torque reference, and the acceleration A second PI controller that receives the deviation of the deceleration torque reference,
The switching means is selected as the measurement side, and the reciprocal of the moment of inertia is replaced with the output of the second PI controller to accelerate or decelerate the motor, and the deviation between the speed reference and the speed feedback signal is 3. The power conversion apparatus according to claim 2, wherein an output of the second PI controller when it becomes a predetermined value or less is stored as a reciprocal of a new moment of inertia. The inertia moment identification means includes
When the moment of inertia is measured, the input of the speed model to the speed control unit is switched to the speed reference, and switching means for turning off the addition correction of the acceleration / deceleration torque reference, the speed model, and the speed feedback signal A third PI controller with the deviation as input,
The switching means is selected as the measurement side, and the reciprocal of the moment of inertia is replaced with the output of the third PI controller to accelerate or decelerate the motor, and the deviation between the speed reference and the speed feedback signal is 3. The power conversion apparatus according to claim 2, wherein an output of the third PI controller when it becomes a predetermined value or less is stored as a reciprocal of a new moment of inertia.

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