JP3676629B2 - Motor control device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a motor control device of a type in which motor drive control of a synchronous motor, an induction motor or the like is performed using a power converter composed of a transistor inverter driven by a PWM method.
[0002]
More particularly, the present invention relates to a motor control device capable of reducing high frequency motor leakage current generated when a plurality of motors are driven using such a power converter and preventing harmful effects such as electromagnetic interference on peripheral devices. It is.
[0003]
[Prior art]
As a control device for AC servo motors such as synchronous motors and induction motors, there is known a type in which energization control for each phase drive coil is performed using a power converter composed of a transistor inverter driven by a PWM method. It has been. In such a control type motor, as the switching frequency of the PWM inverter increases, high-frequency oscillating current generated by switching of the inverter has become a problem.
[0004]
Such high-frequency vibration current flows in the power line between the inverter and the motor, and also flows in the motor ground line as a motor leakage current, which adversely affects the current control of the inverter and generates radiated noise that adversely affects peripheral devices. There is a risk.
[0005]
The high frequency vibration motor leakage current will be described with reference to FIG. As is well known, a drive control unit for a three-phase synchronous motor using a PWM inverter includes a position control unit, a speed control unit, a current control unit, and a power conversion unit. In the figure, only the power conversion unit and the motor coil provided with the inverter are shown. In the drive control unit 200, alternating current from the three-phase alternating current power supply 201 is converted into direct current by the converter 202 and supplied to the voltage source inverter 204 via the smoothing capacitor 203.
[0006]
The inverter 204 includes a pair of upper and lower switching transistors UA and DA, UB and DB, and UC and DC for each phase, and the on / off of these transistors is output from a current control unit (not shown). It is controlled by a gate signal (base drive signal) generated by a PWM control unit 205 that operates based on a voltage command. The PWM control unit 205 performs pulse width modulation based on a triangular waveform carrier 206 to generate each gate signal.
[0007]
Here, an on-delay circuit 207 is provided to prevent a short circuit between the upper and lower arms of the switching transistor. The on delay time is set to be longer than the off time of the transistor. As a result, the input / output characteristics have a dead zone.
[0008]
That is, as shown in FIG. 10, each of the transistors UA to DC is turned on and off at the same time. Due to such on / off switching, the high-frequency vibration current Im flows through the motor coils Lu, Lv and Lw. This high-frequency vibration current cannot be absorbed only by a filter capacitor interposed in the middle, and returns to the AC power source 201 as a high-frequency vibration leakage current Is via the motor ground line.
[0009]
[Problems to be solved by the invention]
Here, in a single motor control device, the adverse effect due to such a leakage current is not so great. However, in a motor control device that controls a plurality of motors at the same time, leakage currents of substantially the same phase are generated from the motors, and these are added to form a high level leakage current. I can't.
[0010]
For example, as shown in FIG. 11, a control device 300 for controlling the driving of six AC motors M1 to M6 includes an AC power supply 201 and a converter 202 that converts AC current into DC current as its power converter. And inverters 204 (1) to 204 (6) attached to each motor to which a direct current is supplied from the converter 202. In this case, the triangular carrier wave 206 is supplied from the common carrier wave generator 210 to the PWM controllers 205 (1) to 205 (6) of the motors.
[0011]
As a result, in each of the motors M1 to M6, the transistors of the inverters 204 (1) to 204 (6) are on / off controlled by a gate signal that is turned on / off in synchronization with the zero cross point of the common carrier wave. Accordingly, as shown in FIG. 12 (a), the phases of the leakage currents I1 to I6 generated in the motors M1 to M6 are substantially matched, and the combined leakage current Is that returns to the AC power supply side via the motor ground line is It becomes a current with a large amplitude. When such a large leakage current Is occurs, a bad effect such as causing a malfunction in a peripheral device or the like occurs.
[0012]
In view of this point, an object of the present invention is to make it possible to significantly reduce motor leakage current with a simple configuration in a motor control device that controls driving of a plurality of AC motors.
[0016]
[Means for Solving the Problems]
In order to solve the above-described problems, the present invention includes a drive control unit that drives and controls each of a plurality of motors, and a carrier wave generator that generates a triangular waveform carrier wave for PWM used in each drive control unit. Each drive control unit includes a transistor inverter that supplies drive power to each motor, a PWM control unit that drives the transistor inverter in a PWM system based on a voltage command and the carrier wave, a current feedback amount and a torque command for each motor. And a current control unit that generates the voltage command and supplies the voltage command to the PWM control unit, at least one of the drive control units inverts the sign of the torque command to the current control unit. A torque command sign inverting unit to be supplied and the current feedback amount by inverting the sign of the current feedback amount; Is characterized by having a current feedback amount sign inversion unit supplies the parts.
[0017]
In the motor control device of the present invention, in the drive control unit including the torque command code inverting unit and the current feedback amount code inverting unit, the drive control of each transistor of the transistor inverter is performed by driving each transistor of the inverter in the other drive control unit. Control is performed in an opposite phase. As a result, the leakage current phase of the motor is almost opposite to the leakage current of the other motors, so that the leakage current as a whole can be reduced.
[0018]
Here, the number of motors is n (n is a positive even number), in other words, the drive control unit is n, and there are n (n is a positive even number) the drive control units. Each of the half of the drive control units is supplied to the current control unit by inverting the sign of the torque command and inverting the sign of the current feedback amount. If the current feedback amount sign inverting unit is provided, the leakage current can be greatly reduced.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of a motor control apparatus to which the present invention is applied will be described below with reference to the drawings.
[0020]
1, Ri system configuration diagram der of the motor control device in the case of driving and controlling the six three-phase synchronous motor, a reference example for explaining the embodiment of the applied motor controller of the present invention. In this example, in order to reduce the leakage current of each motor, the polarity of a part of the carrier wave supplied to each drive control unit is inverted and controlled. As shown in this figure, the motor control device 1 of this example is driven by a three-phase AC power source 2, a converter 3 that converts an AC current supplied therefrom into a DC current, and a DC supplied from the converter 3. There are six drive control units 4 (1) to 4 (6) and synchronous motors M1 to M6 that are driven and controlled by the drive control units 4 (1) to 4 (6).
[0021]
Each drive control unit 4 (1) to 4 (6) has the same configuration, and includes an inverter and a PWM control unit for controlling the drive of the inverter, as will be described later. Each drive control unit 4 (1) to 4 (6) is supplied with triangular-shaped carrier waves 5S (1) to 5S (6) used for pulse width modulation. These carrier waves are obtained via the carrier wave generating unit 5 and the sign inverting unit 6.
[0022]
FIG. 2 is a schematic block diagram showing the main configuration of the drive control unit 4 (1). The other drive control units 4 (2) to 4 (6) have the same configuration as that of the drive control unit 4 (1), and a description thereof will be omitted.
[0023]
In the drive control unit 4 (1), the comparator 31 calculates a deviation between the position command Pcom from the host device (not shown) and the rotor position feedback information of the motor M1. The position control unit 12 generates a speed command based on the position deviation amount. The speed command, the control variable obtained via the speed feedforward unit 11, and the speed feedback information detected by the speed detection unit 13 based on the rotor position feedback information are compared in the comparison unit 32, and are used for speed control. Deviation is determined.
[0024]
The speed control unit 14 generates a torque command Tcom based on the speed control deviation and outputs the torque command Tcom to the current control unit 16. Rotor magnetic pole position information is fed back to the current control unit 16 via the magnetic pole position detection unit 17, and the driving currents of the U-phase driving coil and the V-phase driving coil of the motor detected by the current sensors 22a and 22b. Is supplied as a current feedback amount. The current control unit 16 compares these feedback amounts with the torque command Tcom to generate a three-phase voltage command.
[0025]
The voltage command is supplied to the PWM control unit 18. Based on the voltage command, the PWM control unit 18 uses the carrier wave 5S (1) supplied from the carrier wave generation unit 5 via the sign inversion unit 6 to generate a rectangular wave gate signal for each phase pair. These gate signals are supplied to the voltage source inverter 19, and on / off control of a pair of upper and lower power transistors constituting each inverter 19 is performed. As a result, three-phase drive currents Iu, Iv and Iw are generated from the DC voltage supplied to the inverter 19 via the converter 3, and these are supplied to the drive coils of the respective phases of the synchronous motor M1.
[0026]
The rotor rotational position of the synchronous motor M1 is detected by the rotary encoder 21, the rotor magnetic pole position is detected by the magnetic pole position detector 17 based on the encoder output, and the rotor position is detected by the position detector 15.
[0027]
FIG. 3 is a schematic block diagram of the current control unit 16. As shown in FIG. 3, the current control unit 16 includes the torque command Tcom and the U-phase and V-phase supplied from the sine wave reference table 33. Each of the current distribution signals is multiplied by multipliers 25a and 25b, the multiplication values are compared in comparison units 33a and 33b, and the comparison results are supplied to current control circuits 24a and 24b made of current amplifiers. A V-phase current command is generated. Further, the comparison results of the comparison units 33a and 33b are compared in the comparison unit 33c, and the output of the comparison unit 33c is supplied to a current control circuit 24c formed of a current amplifier to generate a W-phase current command.
[0028]
FIG. 4 is a schematic block diagram of the above-described PWM control unit 18. As shown in the figure, the PWM control unit 18 supplies voltage commands for each phase to the comparison circuits 26a, 26b, and 26c, respectively. The carrier wave 5S (1) is supplied from the carrier wave generating circuit 5 through the sign inverting unit 6. Each of the comparison circuits 26a, 26b, and 26c generates rectangular wave signals 100a, 100b, and 100c having a duty ratio based on a voltage command. A pair of gate signals (base drive signals) 101a and 102a, 101b and 102b, and 101c and 102c, each having a phase inverted, are generated.
[0029]
FIG. 5 shows an output signal 100a for U phase and a pair of gate signals 101a and 102a. As can be seen from this timing chart, the rise time of each gate signal is delayed by Td by the on-delay circuit 27a.
[0030]
Here, the carrier waves 5S (1), 5S (3) and 5S () supplied to the drive control units 4 (1), 4 (3) and 4 (5) from the sign inverting unit 6 of the motor control device 1 of this example. 5) is the same as the carrier wave 5S generated from the carrier wave generator 5. On the other hand, the carrier waves 5S (2), 5S (4) and 5S (6) supplied to the remaining half of the drive control units 4 (2), 4 (4) and 4 (6) The sign inverting unit 6 inverts the positive and negative signs of the carrier wave 5S generated from the carrier wave 5S to obtain a triangular waveform carrier wave having an opposite phase.
[0031]
As a result, the drive control of the inverters in the drive control units 4 (2), 4 (4) and 4 (6) is opposite to the inverters in the drive control units 4 (1), 4 (3) and 4 (5). It becomes a phase. Therefore, in this example, the high-frequency vibration leakage current generated due to the inverter on / off switching control in each of the synchronous motors M1 to M6 is the leakage current I1 of the synchronous motors M1, M3, and M5 as shown in FIG. , I3 and I5 are substantially in phase. Similarly, the phases of the leak currents I2, I4, and I6 of the synchronous motors M2, M4, and M6 also match. However, the phases of the leak currents I1, I3, and I5 are almost opposite to the phases of the leak currents I2, I4, and I6. As a result, the sum of these leak currents cancels each other out to a very small current Is, and adverse effects on peripheral devices and the like can be suppressed or avoided.
[0032]
In this example, a common carrier generation unit 5 is provided. However, each of the drive control units 4 (1) to 4 (6) is provided with a carrier generation unit 5, and each carrier has the same phase. Thus, synchronization may be taken so that the sign of the carrier wave is inverted and controlled in each drive control unit.
[0033]
( Example )
Next, examples of the present invention will be described. In this example, in order to reduce the leakage current of the motors M1 to M6, instead of the inversion control portion of the polarity of the carrier supplied to the drive control unit, what the configuration shown in FIG. 6 as a drive control unit Adopt .
[0034]
In the drive control unit 4A shown in FIG. 6, portions corresponding to the respective portions of the drive control unit 4 (1) are denoted by the same reference numerals, and description thereof is omitted. In the drive control unit 4 </ b> A of this example, a torque command sign reversing unit 23 b is disposed between the speed control unit 14 and the current control unit 16, and the sign of the torque command is reversed and supplied to the current control unit 16. Further, the current feedback amount obtained from the current sensors 22a and 22b is supplied to the current control unit 16 with the polarity reversed by the current feedback amount sign inverting units 23f and 23g. Further, the gate signals 101a and 102a, 101b and 102b, and 101c and 102c of each phase output from the PWM control unit 18 are respectively supplied to the bases of the power transistors of each phase upside down in the inverter 19. Yes.
[0035]
FIG. 7 shows an example of a motor control device for driving and controlling six synchronous motors including the drive control unit having this configuration. In this motor control device 1A, the drive control unit 4A described above is adopted as the drive control unit for the motors M1, M3, and M5, and the drive control unit 4 (described above as the drive control unit for the other motors M2, M4, and M6). 1) is adopted. A common carrier wave is supplied to each drive control unit.
[0036]
Also in the motor control apparatus 1A having this configuration, the drive control of the inverters in the drive control units of the motors M1, M3, and M5 is performed by driving the remaining motors M2, M4, and M6 by providing the sign inversion units 23b, 23f, and 23g. The drive control of the inverter in the control unit is performed in the opposite phase. Therefore, as in the case of the motor control unit 1 described above, the generated leakage currents of the respective motors are almost opposite in phase between the motors M1, 3, 5 and the motors M2, 4, 6, and the two sets of leakage currents are mutually connected. As a result, the leakage current as a whole is greatly reduced.
[0037]
(Other embodiments)
In each of the above examples, the drive control phases of the inverters are reversed by half, but the drive control unit is not limited to half and is equivalent to one, two, four, or five. May be driven so as to have an opposite phase. Furthermore, the number of motors to be controlled by the motor control device of the present invention is not limited to six, and may be five or less, or may be seven or more.
[0038]
Further, the current control unit is not limited to the control unit 16 configured as shown in FIG. 2, and may have a function of generating a voltage command using the magnetic pole position, the current feedback amount, and the torque command. Of course. For example, it is a matter of course that a current control unit including a coordinate conversion unit as shown in FIG. 8 can be used.
[0039]
【The invention's effect】
As described above, the present invention provides a motor control device having a drive control unit including an inverter that drives each motor by the PWM method. The drive control of the inverter in the drive control unit of at least one motor The phase is opposite to that of the drive control of the inverter in the drive control unit. Therefore, according to the present invention, the phase of the leakage current of the motor provided with the inverter controlled in the opposite phase is also in the opposite phase. Therefore, the motor leakage current as a whole can be reduced by the leakage current having the opposite phase. As described above, according to the present invention, it is possible to reduce the generation of the motor leakage current to a level that does not cause a practical problem by simply adding a simple circuit configuration.
[Brief description of the drawings]
FIG. 1 is a schematic block diagram of a motor control apparatus according to a reference example .
FIG. 2 is a schematic block diagram of the drive control unit of FIG.
3 is a schematic block diagram of a current control unit in FIG. 2;
4 is a schematic block diagram of a PWM control unit in FIG. 2;
FIG. 5 is a timing chart of gate signals.
FIG. 6 is a schematic block diagram illustrating a drive control unit of the motor control device according to the embodiment .
7 is a schematic block diagram of a motor control device including the drive control unit of FIG.
FIG. 8 is a schematic block diagram illustrating another circuit example of the current control unit illustrated in FIG. 3;
FIG. 9 is a schematic block diagram of a conventional motor control device.
10 is a timing chart of a carrier wave, a gate signal, and a leakage current in the apparatus of FIG.
FIG. 11 is a schematic block diagram showing a conventional example of a control device for controlling a plurality of motors.
12A is a timing chart showing motor leakage current generated from a conventional motor control apparatus, and FIG. 12B is a timing chart showing motor leakage current generated in the motor control apparatus according to the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Motor control apparatus 2 AC power supply 3 Converter 4, 4A, 4 (1) thru | or 4 (6) Drive control unit 5 Carrier wave generation part 5S (1) thru | or 5S (6) Carrier wave 6 Carrier wave code inversion part 16 Current control part 18 PWM Control unit 19 Voltage source inverter M1 to M6 Motor 23b Torque command sign reversing unit 23f, 23g Current feedback amount code reversing unit I1 to I6 Leakage current Is from each motor Is combined leakage current

Claims (2)

A drive control unit that drives and controls each of the plurality of motors; and a carrier wave generation unit that generates a carrier wave of a triangular waveform for PWM used in each drive control unit. Each drive control unit supplies drive power to each motor. A transistor inverter to be supplied, a PWM control unit that drives the transistor inverter in a PWM system based on the voltage command and the carrier wave, and the PWM control unit that generates the voltage command based on a current feedback amount and a torque command of each motor In a motor control device having a current control unit for supplying to
At least one of the drive control units reverses the sign of the torque command and supplies it to the current control unit, and reverses the sign of the current feedback amount and supplies current to the current control unit A motor control device having a feedback amount code inverting unit. In claim 1,
n (n is a positive even number) of the drive control units, and half of these drive control units invert torque command code inversion of the torque command code and supply it to the current control unit And a current feedback amount sign inverting unit that inverts the sign of the current feedback amount and supplies it to the current control unit.

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