JP4698312B2 - Power converter - Google Patents

Description

  The present invention relates to a power converter for driving an electric motor used in a process line in which a plurality of electric motors are used.

  2. Description of the Related Art Conventionally, a power conversion device that drives an electric motor used in a process line has adopted a configuration in which a DC voltage is converted into an alternating current by an inverter, and the electric motor is driven with this alternating current output to generate necessary speed and torque. Since the process line is composed of a plurality of stands, a plurality of power conversion devices as described above are used. A speed sensor is connected to each electric motor to detect the magnetic pole position or speed of the electric motor.

  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.

Here, the speed reference is a reference for determining the speed of the entire process line, and is commonly given to each power conversion device from the controller that controls the entire process line, and maintains the uniform speed of each stand of the process line. I am doing so. On the other hand, when control specific to each stand is required, for example, when controlling the tension of the strip between two stands, a torque command or current command for correction is externally applied to the torque reference or current reference of each stand. Are added for correction (for example, see Patent Document 1).
Japanese Patent No. 2721409 (page 2-3, FIG. 1)

  The technique disclosed in Patent Document 1 is effective for needs for controlling the torque of an electric motor used for an individual stand in a process line with a response faster than a response of speed control. However, it is difficult to apply when the entire process line is controlled with a common speed reference and speed correction is desired with a response faster than the common speed control response.

  For example, in a process line, when the resonance of the mechanical system determined by the roll of the stand, the electric motor, and the shaft needs to have a low response for only one stand, it is necessary to match the low response for the other stand as well. is there. For this reason, if the method of adding the speed correction to the common speed reference is used, even a stand that can take a high speed response to the input of the speed correction signal from the outside will have a low response. Therefore, in the method of adding the above speed correction to the common speed reference, the control is performed with a low response even at the time of acceleration or deceleration where speed correction is particularly necessary, and the productivity of the entire process line is lowered. There was a problem of doing.

  The present invention has been made in order to solve the above-described problems. In the process line, the power conversion apparatus improves the process line productivity by making the response to the speed correction faster than the response to the common speed reference. The purpose is to provide.

  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 A speed model computing unit for computing the speed model, a speed correction command given from the outside, and a speed feedback signal obtained from the speed detecting means, and adding the acceleration / deceleration torque reference to the output to obtain a torque reference And a current of the excitation shaft and torque shaft of the motor based on the torque reference and the current detected by the current detection means It is characterized in that a vector control or sensorless vector control means for controlling independently.

  According to the present invention, since the speed model calculation is added to the input of the speed controller, the response to the speed correction can be made faster than the response to the common speed reference, and the power for improving the productivity of the process line. A conversion device can be provided.

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

  The first embodiment 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 31. The output of the speed model calculator 31, the speed feedback signal and the speed correction signal given from outside are input to the speed controller 32. The speed controller 32 controls and controls these signals, and provides the output to the vector controller 33 as a torque reference. The vector controller 33 decomposes 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 calculates the deviation to control the current. Do. 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, and the magnetic flux current controller 36 calculates the deviation to control the current. I do. 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 internal configuration of the speed model calculator 31 and the speed controller 32 is shown in FIG. The speed reference is supplied to the PI controller 311 of the speed model calculator 31, and the output is negatively fed back to the input of the PI controller 31 via the integration circuit 312 having the inertia moment J of the load of the electric motor 2. The output of the integration circuit 312 is negatively fed back to the input side of the integration circuit 312 via the pseudo differentiation circuit 313. The output of the integration circuit 312 is the speed model signal, and the input of the integration circuit 312 is the torque reference 1.

  The speed model signal is added to a speed correction signal supplied from the outside inside the speed control unit 32, the speed feedback signal is subtracted from the corrected speed model signal, and the deviation is calculated by the PI controller 321. Control. The speed feedback signal is supplied to the pseudo-differential circuit 322, and the output of the pseudo-differential circuit 322 is subtracted from the output of the PI controller 321, and the torque reference 1 is added to the subtracted output, resulting in a vector. A torque reference that is input to the controller 33 is obtained.

  The effect in the above structure is demonstrated below.

  The input of the speed model calculator 31 is the deviation between the speed reference and the speed model, and the torque reference 1 obtained by PI control of this represents the torque required for the motor 2 to accelerate and decelerate. In the torque reference 1 to speed model, since the amount obtained by pseudo-differentiating the speed model is subtracted from the output of the PI controller 311, the signal is delayed by this pseudo-differential amount, and overshoot for the change in signal can be suppressed. It is like that. If the total moment of inertia of the rotor of the motor 2 and the load is used as the moment of inertia J used in the integration circuit 313, the speed model that is the output of the speed model calculator 31 has a signal corresponding to the pseudo differential amount. This represents the estimated speed of the delayed electric motor 2. The pseudo-differential circuit means a so-called incomplete differential circuit whose gain is not infinite in the high frequency range.

  The PI controller 321 in the speed controller 32 performs PI control on the deviation between the corrected speed model obtained by adding the speed correction signal given from the outside to the speed model and the speed feedback signal, and the torque reference 1 is added to the output. As a result, a torque reference as an input to the vector controller 33 is obtained. The pseudo-differential circuit 322 performs the same operation as the pseudo-differential circuit 312 used in the speed model computing unit 31, and the output signal is delayed by the pseudo-differential amount, but the output overshoot with respect to the change of the input signal is suppressed.

  In the operation as described above, by appropriately selecting the control parameters of the control elements such as the pseudo-differential circuits 313 and 322, it operates with a relatively slow response with respect to the overall speed reference, and for speed correction. Can realize a power converter that operates with a faster response. In addition, in each control element shown in FIG.1 (b), illustration of a gain constant is abbreviate | omitted.

  FIG. 2 shows a system configuration diagram when this power conversion apparatus is applied to an actual process line. In FIG. 2, stands 6A, 6B and 6C constituting the process line are driven by electric motors 2A, 2B and 2C, respectively, and electric motors 2A, 2B and 2C are respectively controlled by inverters 1A, 3A, 3B and 3C controlled by control units 3A, 3B and 3C. Driven by 1B and 1C. A common speed reference of the process line is given to the respective speed model calculation units of the control units 3A, 3B, and 3C, and the speed correction unique to each stand 6A, 6B, and 6C is the speed control of each of the control units 3A, 3B, and 3C. Given directly to the vessel.

  With the configuration of FIG. 2, the speed reference operates with a slow response determined by the control constant of the speed model, and the speed correction operates with a faster response bypassing the response delay of the speed model. A power converter can be realized.

  In FIG. 2, the power converters applied to the stands 6A, 6B, and 6C are all the power converters according to the present invention shown in FIG. 1, but not all of them are necessarily required. . For example, when it is necessary to correct a fast response speed for a specific part of an existing process line composed of power converters with a relatively slow speed response, only the specific part of the stand is required. What is necessary is just to apply the power converter device of this invention shown in FIG.

  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.

  FIG. 3 is a block configuration diagram of a speed model calculation unit and a speed control unit of the power conversion apparatus according to the second embodiment of the present invention. In the second embodiment, the same parts as those in the block configuration diagram of the speed model calculation unit and the speed control unit of the power conversion apparatus according to the first embodiment shown in FIG. 1B are denoted by the same reference numerals, and the description thereof is omitted. To do. The second embodiment is different from the first embodiment in that a subtracter 323 for subtracting the speed model is added to the input of the pseudo-differential circuit 322 of the speed control unit 32A.

  The control characteristic of the speed control unit 32 shown in FIG. 1B has a delay element determined by the control constant of the pseudo-differential circuit 322 as described above. Therefore, in order to compensate for this delay element in a state in which the function of overshoot suppression of the pseudo-differential circuit 322 is utilized, the speed model is given to the pseudo-differential circuit having the same control constant as that of the pseudo-differential circuit 322, and its output May be added to the output of the pseudo-differential circuit 322 to compensate. That is, this is the same as subtracting the speed model on the input side of the pseudo-differential circuit 322. Therefore, it is possible to realize this by adopting the speed control unit 32A shown in FIG.

  According to the second embodiment, since the control delay of the pseudo-differential circuit 322 is compensated, the speed deviation during acceleration / deceleration can be reduced.

  FIG. 4 is a block configuration diagram of a speed model calculation unit and a speed control unit of the power conversion apparatus according to the third embodiment of the present invention. About each part of this Example 3, the part same as each part of the block block diagram of the speed model calculating part and speed control part of the power converter which concerns on Example 2 of FIG. 3 is shown with the same code | symbol, and the description is abbreviate | omitted. The third embodiment is different from the second embodiment in that the speed control unit 32B is configured to provide the speed model to the subtracter 323 via the filter 324.

  Since the filter 324 cuts high-frequency components, stable control characteristics against noise or the like can be obtained by compensating for the control delay of the pseudo-differential circuit 322 described above via the filter 324.

  FIG. 5 is a block configuration diagram of a speed model calculation unit and a speed control unit of the power conversion apparatus according to the fourth embodiment of the present invention. The same parts as those in the block configuration diagram of the speed model calculation unit and the speed control unit of the power conversion device according to the first embodiment of FIG. To do. The fourth embodiment is different from the first embodiment in that a subtracter 325 for calculating the difference between the speed model and the speed feedback signal is provided in the speed control unit 32C, and the output of the subtractor 325 is torqued via the filter 326. It is the point which comprised so that it might add to a reference | standard.

  The speed model represents an ideal estimated speed that does not consider shaft vibration due to mechanical resonance, etc. If the torque reference is corrected by the deviation between this speed model and the actual speed feedback signal, the mechanical system It operates to suppress vibrations caused by resonance. Note that harmonic components are removed by the filter 326 to stabilize the control.

  FIG. 6 is a block configuration diagram of a speed model calculation unit and a speed control unit of the power conversion apparatus according to the fifth embodiment of the present invention. About each part of this Example 5, the same part as each part of the block block diagram of the speed model calculating part and speed control part of the power converter which concerns on Example 4 of FIG. 5 is shown with the same code | symbol, and the description is abbreviate | omitted. The fifth embodiment is different from the fourth embodiment in that a differentiating circuit 327 is provided at the input portion of the filter 326 in the speed control unit 32D.

  According to the fifth embodiment, the effect of the differentiating circuit 327 makes it possible to speed up the response to the shaft vibration and more strongly suppress the vibration caused by the resonance of the mechanical system.

The block block diagram of the power converter device which concerns on Example 1 of this invention. The system block diagram when the power converter device of Example 1 is applied to an actual process line. The block block diagram of the speed model calculating part and speed control part of the power converter device which concern on Example 2 of this invention. The block block diagram of the speed model calculating part and speed control part of the power converter device which concern on Example 3 of this invention. The block block diagram of the speed model calculating part and speed control part of the power converter device which concern on Example 4 of this invention. The block diagram of the speed model calculating part and speed control part of the power converter device which concerns on Example 5 of this invention.

Explanation of symbols

1, 1A, 1B, 1C Inverter 2, 2A, 2B, 2C Electric motor 3, 3A, 3B, 3C Controller 4 Speed sensor 5 Current detector 6 Current controller 31 Speed model calculator 311 PI controller 312 Pseudo-differential circuit 313 Integrator 32, 32A, 32B, 32C, 32D Speed control unit 321 PI controller 322 Pseudo-differential circuit 323 Subtractor 324 Filter 325 Subtractor 326 Filter 327 Differentiating circuit 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

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 inputs the speed model and a speed correction command given from the outside and a speed feedback signal obtained from the speed detection means, adds the acceleration / deceleration torque reference to the output thereof, and outputs a torque reference;
Power conversion comprising: vector control or sensorless vector control means for independently controlling currents 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 apparatus. The speed controller is
PI control is performed by the PI controller for the difference between the speed model and the speed correction command and the deviation of the speed feedback signal;
The power converter according to claim 1, wherein an output of the pseudo-differential circuit having the speed feedback signal as an input is subtracted from the output of the PI controller to obtain the output. The speed controller is
PI control is performed by the PI controller for the difference between the speed model and the speed correction command and the deviation of the speed feedback signal;
2. The power according to claim 1, wherein the output of the pseudo-differential circuit that receives the deviation between the speed feedback signal and the speed model is subtracted from the output of the PI controller to obtain the output. Conversion device. The speed controller is
PI control is performed on the sum of the speed reference and the speed correction command and the deviation of the speed feedback signal with a PI controller;
The output of the pseudo-differential circuit that receives the deviation between the speed feedback signal and the signal obtained by filtering the speed model is subtracted from the output of the PI controller to obtain the output. The power converter according to 1.   The output of the filter circuit which inputs the deviation between the speed model and the speed feedback signal is added to the output of the speed control unit. Power converter.   The power converter according to claim 5, wherein a differential circuit is provided at an input of the filter circuit. The speed model calculation unit includes:
The PI controller controls the deviation between the speed reference and the speed model,
Acceleration / deceleration torque reference is obtained by subtracting the output of the pseudo-differential circuit having the speed model as an input from the output of the PI controller,
7. The speed model according to claim 1, wherein the speed model is obtained by multiplying the acceleration / deceleration torque reference by an integration circuit having an inertia moment of the motor and its load. The power converter described.

Images