JPH0487592A - Speed controller for wound-rotor type induction motor - Google Patents

Abstract

PURPOSE:To suppress a harmonic current and to reduce the capacity of an AC/DC converter by PWM-controlling the converter based on a current reference signal having the same phase as the secondary voltage phase of a wound-rotor type induction motor in proportion to a deviation in amplitudes between a speed detection signal of the motor and a speed reference signal. CONSTITUTION:A current reference signal is proportional in amplitude to a deviation signal between a speed detection signal of a motor 2 and a speed reference signal, and has the same phase as the secondary voltage phase of the motor. A motor secondary current detected by a secondary current detector 11 and a current reference signal are applied to a secondary current controller 12, its deviation signal becomes an output signal, and a PWM controller 13 is controlled by the signal. If the voltage of a commutation capacitor 20 becomes higher than the voltage of a power capacitor 20A, the capacitor 20A is charged. The DC voltage of the capacitor 20A is applied to a DC/AC converter 22 and converted to an AC. The converted AC is regenerated to an AC power source 1 through a reactor 21 and a transformer 25.

Description

[Detailed Description of the Invention] [Purpose of the Invention (Industrial Application Field) The present invention relates to a speed control device for a wound induction motor, and particularly relates to speed control using PWM (Pulse Width Modulation) control and speed control that occurs at this time. The present invention relates to a speed control device when secondary power of an electric motor is regenerated to an AC power source by a PWM control device.

(Prior Art) As shown in FIG. 7, speed control by a thyristor Serbius device that regenerates the secondary power of a wound induction motor (hereinafter simply referred to as the motor) 2 to an AC power supply 1 to control the speed of the motor 2 is performed as shown in FIG. The secondary power is converted into direct current by a rectifier 110 and regenerated into an alternating current power source by a silice inverter 112.

Conventionally, this device has mainly been used to drive loads such as fans and pumps having square torque characteristics, and the characteristics will be explained below.

FIG. 6 is a characteristic showing a general relationship between the secondary human power pt of the electric motor, its shaft output PL, and the secondary power PC when driving a square torque characteristic load.

The secondary power PC is expressed by the difference between the secondary human power Pi and the shaft output PL.

PC-Pi -PL River (1) Also, from the characteristic that the load torque is proportional to the square of the sub-S, PC-PH (S2-S3)... (2) As a function of the S-sub, equation (2) Hail to you.

However, PM is the motor synchronous output (2) Karasuberi S-(1/3)X The secondary power PC is maximum at the motor synchronous speed, and its value is 15% of the motor synchronous output.

In the circuit diagram of the thyristor Serbius device shown in FIG. 7, the capacity of the device is determined by the product of the maximum secondary voltage and maximum secondary current to be controlled.

Although the maximum secondary power PC input to this device is 15% of the motor synchronous output, the capacity of the device has generally been determined at a much larger value. For example, if the control range is 50% of the synchronous speed, the capacity of the device is 50%.
This is illustrated by an example such as XPM.

Also, a large DC reactor 111 is installed in the DC circuit of this device.
, the secondary current of the motor 2 becomes a square wave whose peak value is controlled to be constant, and contains many harmonic currents as shown in equation (3).

(6n±1)Sr ・(3) However, S
f is the secondary frequency (S: slip, f: power supply frequency) Therefore, on the primary side of the motor 2, the harmonic component of equation (3) is caused by the slip action to the harmonic component of equation (4) (1±6 n S)
r = 14) It flows as a harmonic current and mutually interferes with the power supply frequency r, causing a low-order pulsating current to flow.

Similarly, the secondary current of this electric motor 2 flows to the power supply side through the thyrisk inverter 112, but this current also becomes a square wave and flows including harmonics of equation (5).

(6n ±1)f...
・(5) (Problem to be solved by the invention) As described above, in the conventional speed control device using thyristor Servian control, a device larger than the secondary power generated by the electric motor 2 is required, and the speed approaches the synchronous speed. As the active secondary power becomes almost zero, the device becomes a reactive power supply device. Therefore, there is a problem in that large equipment must be provided to improve the power factor of the electric power.

Furthermore, since a low-frequency pulsating current flows in the primary current of the electric motor 2, the electric motor 2 generates low-frequency torque pulsations. For this reason, it is necessary to take measures against mechanical vibration, especially in load equipment such as fans and floors with large inertia, and in some cases there is a problem in that the operating range has to be limited.

The present invention has been made to solve the above-mentioned problems, and its purpose is to limit the motor secondary current to a sine wave so that the motor primary current does not include low-order pulsating current. and to provide a speed control device for a wound induction motor, which regenerates a sinusoidal current with a power factor of 1 to an alternating current power source and adjusts the device capacity to match the amount of secondary power generated by the motor. It is in.

[Structure of the Invention (Means for Solving the Problems)] In order to achieve the above-mentioned object, the present invention has a secondary winding provided independently for each phase, and a primary winding connected to the secondary winding of the wound induction motor. A transformer is connected to the secondary winding, and a secondary winding of the transformer is connected to each phase input terminal on the AC side, respectively, and is connected via a diode to the DC side output terminal of an AC/DC converter that is PWM controlled. a commutating capacitor; and means for calculating a current reference signal whose amplitude is proportional to a deviation signal between the speed detection signal of the wound induction motor and the speed reference signal and whose phase is the same as the secondary voltage phase of the wound induction motor. and PWM IJ control means for PWM controlling the AC/DC converter according to the deviation between the current reference signal and the secondary current detection signal of the wound induction motor, inputting the DC voltage of the commutating capacitor. The DC/AC converter is configured with a DC/AC converter that converts DC into AC and regenerates the AC power to the AC power supply, and further, the DC/AC converter has a secondary winding provided independently for each phase and a primary winding. a second transformer having a line connected to the AC power source; a power capacitor connected between terminals of the commutating capacitor via a second diode; and a DC side input terminal connected to the power capacitor via a reactor. a DC-AC converter connected to the DC-AC converter, each phase output terminal on the AC side being connected to each secondary winding of the second transformer; and a deviation signal having an amplitude between the voltage detection signal of the power capacitor and the voltage reference signal. means for calculating a second current reference signal that is proportional to and has the same phase as the voltage phase of the AC power source, and according to a deviation between the second current reference signal and a regenerative current detection signal to the AC power source. PWM the DC/AC converter
The present invention is characterized in that it is configured with a second PWM control means for controlling.

(Function) With the above configuration, the amplitude is proportional to the deviation between the speed detection signal of the wound induction motor and the speed reference signal, and the current reference signal has the same phase as the secondary voltage phase of the wound induction motor. By performing PWM control on the AC/DC converter based on the PWM control, a PWM-controlled sine wave current in phase with the secondary voltage can be passed through the secondary winding of the wound induction motor. A second signal whose phase is proportional to the deviation between the detection signal and the voltage reference signal and whose phase is the same as the voltage phase of the AC power supply.
By performing PWM control on the DC/AC converter based on the current reference signal, the AC power source can regenerate a sinusoidal current with a power factor of 1.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings. FIG. 1 is a configuration diagram showing an embodiment of the present invention, in which 1 is an AC power source, 2 is a wound induction motor (hereinafter simply referred to as a motor), and 3 is a secondary winding of motor 2 whose primary winding is connected to,
A transformer in which a secondary winding is provided independently for each phase,
Reference numeral 4 indicates an AC/DC converter which is PWM-controlled and has the secondary winding of the transformer 3 connected to each phase input terminal on the AC side, and 5 is a diode through which the commutating capacitor 20 is charged.

FIG. 2 shows the AC/DC converter 4 of FIG. 1 which is PWM controlled.
FIG. 2 is a configuration diagram showing a specific configuration example and the connection relationship between the secondary winding of the transformer 3 and the secondary winding of the transformer 3; Returning to Figure 1 again, motor 2
The speed of is set by a speed setter 6, and the set value and the speed detection value detected by a speed detector 7 are input to a speed control circuit 8.

The speed control circuit 8 outputs a deviation signal between the set value and the detected value and inputs it to a multiplier 10, which further includes a transformer 9.
A signal corresponding to the secondary voltage of the electric motor 2 detected by the multiplier 10 is inputted, and a current reference signal is obtained at the output of the multiplier 10.

The current reference signal is a signal whose amplitude is proportional to the deviation signal between the speed detection signal of the electric motor 2 and the speed reference signal, and whose phase is the same as the secondary voltage phase of the electric motor 2.

The motor secondary current detected by the secondary current detector 11 and the current reference signal are given to the secondary current control circuit 12, and the deviation signal becomes an output signal.
Control circuit 13 is controlled.

Next, the configuration of the DC/AC converter that regenerates the secondary power stored in the commutating capacitor 20 to the AC power supply 1 will be described.

When the voltage of commutating capacitor 20 becomes higher than the voltage of power capacitor 2OA, power capacitor 2OA is charged via diode 5A. The DC voltage of the power capacitor 2OA is applied to the DC/AC converter 22 via the handle 21 and converted into AC.

The AC converted by the DC/AC converter 22 is transferred to the reactor 2
1 and the transformer 25 to the AC power supply 1.

Figure 4 shows GTOs 201 to 212 and diodes 301.
A specific example of the configuration of the DC/AC converter 22 shown in FIG.
This shows the connection diagram with 5W, 24A, 24B, 24
C corresponds to the glue handle 24 in FIG. 1, and is a reactor inserted between the secondary winding of the transformer 25 and the AC output of the DC/AC converter 22.

Returning to FIG. 1 again, the voltage on the DC input side of the DC/AC converter 22 is set by the voltage setter 26, and the set value and the voltage detection value detected by the voltage detector 20B are sent to the voltage control circuit 27. input. The output of the voltage control circuit 27 is applied to one input of the multiplier 29, and a voltage corresponding to the voltage of the AC power supply 1 input to the other input is detected by the transformer 28 and applied. A current reference is obtained which is proportional to the output and whose phase is the same as the voltage phase of the AC power supply l.

The current control circuit 30 uses the current reference signal and the current detector 23.
Compare the output current of the DC/AC converter 22 detected by
The deviation signal is applied to the PWM control circuit 31. The DC/AC converter 22 outputs P in response to the output signal of the current control circuit 30.
The AC power supply 1 is PWM-controlled by the WM control circuit 31.
A current having the same phase as the voltage is regenerated to the AC power supply 1.

Next, the operation of the embodiment of the present invention having the above-mentioned configuration will be explained as follows.
This will be explained with reference to FIGS. 2 and 3.

Assuming that the electric motor 2 is rotating at a predetermined rotational speed, a sine wave voltage is generated in its secondary winding, and this AC voltage is applied to the AC/DC converter 4 via the transformer 3.

In Figure 2, the voltage of the U-phase winding 3U of the transformer 3 is
When it is induced in the direction of the arrow, that is, the GTO 45 is controlled on and off at a predetermined period during the positive half cycle of the sine wave, and when it is induced in the direction of the arrow, that is, during the negative half cycle of the sine wave. If the GTO 46 is controlled on and off at a predetermined period during the period of , a sinusoidal current in phase with the secondary voltage can be caused to flow. On/off control of GTO45 and GTO46 is PW
This is performed by the M control circuit 13.

Figure 3 is a diagram for explaining the on/off operation of the GTO.
In the figure, X indicates a carrier signal with a frequency sufficiently higher than the secondary frequency of the motor 2, e is an input signal to the PWM control circuit 13, and the amplitude of this signal e is the amplitude of the current reference signal output from the multiplier 10. , and its phase is a signal having the same phase as the secondary voltage phase, and e is an inverted signal of e.

The PWM control circuit 13 compares the input signal e and the carrier signal If e, signal gB of “0”
Calculate.

Further, the signal gA and the signal gB are logically operated to calculate a signal for turning on and off the GTO, and the AC/DC converter 4 is controlled by PWM. That is, if the period of the positive half cycle of the signal e is TA, and the period of the positive half cycle of the signal e is TB, the GTO 45 is on/off controlled during the period TA, and the GTO 45 is controlled on/off during the period TB.
The AC/DC converter 4 is PWM controlled by the signal GO that turns on/off the TO 46.

Since the {circle around (2)} phase and the W phase are also PWM controlled in the same manner as the U phase, a description of the V phase and W phase will be omitted.

FIG. 3 shows that the GTO 45 is turned on and off 11 times during the TA period, and the GTO 46 is turned on and off 11 times during the TB period. Further, the sine wave indicated by a dotted line in the signal GO in FIG. 3 indicates a secondary voltage.

Now, during the TA off period, when an on signal is given to GTO45, the U-phase current iu changes from U-phase winding -3U → diode 41 → G
It flows in the closed circuit of TO45-U phase winding 3U. The current increase rate at this time is mainly suppressed by the inductance of the secondary winding of the motor 2. Next, when an off signal is given to the GTO45, the GTO45 turns off.The U-phase current iu that has been flowing in the closed circuit until now is changed from the U-phase winding 3U to the diode 41 to the diode 5 to the commutating capacitor 20 to the diode 44 to U.
It flows in the closed circuit of phase winding 3U. In this way, if GTO45 is turned on during the TA off period, the former is closed circuit, and if GTO45 is turned off, the latter is closed circuit.
A phase current iu flows.

Also, the U-phase current iu changes from U-phase winding 3U to diode 41→
Diode 5 → Commutation capacitor 20 → Diode 44 →
When flowing through the closed circuit of the U-phase winding 3U, the secondary power of the motor 2 is accumulated in the commutating capacitor 20.

Next, during the period TH, when an on signal is applied to the GTO 46, the U-phase current iu flows in a closed circuit of the U-phase winding 3U -> the GTO 46 - the diode 42 - the U-phase winding 3U. Next GT
When an off signal is given to O46, GTO46 turns off, but the U-phase current iu that has been flowing in the closed circuit until now is transferred to U-phase winding 3.
U → Diode 43 → Diode 5 → Commutation capacitor 2
The current flows in a closed circuit of 0→diode 42→U phase winding 3U.

In this way, when the GTO 46 is turned on during the TB off period, the U-phase current iu flows in the former closed circuit, and when the GTO 46 is turned off, the U-phase current iu flows in the latter closed circuit. Also, when the U-phase current iu flows in the closed circuit of U-phase winding 3U → diode 43 - diode 5 → commutating capacitor 20 → diode 42 → U-phase winding 3U, the secondary power of motor 2 flows through the commutating capacitor. 20 is accumulated.

As described above, the on signal and off signal are input to the GTO 45 during the period TA. Also, during period TB, an on signal and an off signal are input to the GTO 46. As a result, the U-phase current iu is synchronized with the input signal e, and in its positive half cycle TA, the U-phase current iu becomes GT
When O45 turns on, it short-circuits with the secondary side of motor 2 and flows.
When turned off, the current flows through the commutating capacitor 20. Further, in the negative half cycle TB, the GTO performs the same operation so that the U-phase current iu flows.

As described above, the secondary current of the motor 2 is PWM-controlled by the AC/DC converter 4 using the current reference signal which sets the speed control output signal to the peak value and becomes a sine wave with the same phase as the secondary voltage of the motor 2. This is a secondary current that does not contain harmonics.

Therefore, on the primary side of the electric motor 2, A pulsating current of (l±6sn)f' does not occur.

Also, when the GTO of the AC/DC converter 4 is turned on, the electric motor 2
Since the power stored in the inductance flows to the commutating capacitor 20 when the GTO is turned off, the secondary power PC of the motor shown in FIG. 6 can be stored in the commutating capacitor 20.

Next, the operation when regenerating the secondary power accumulated in the commutating capacitor 20 to the AC power supply 1 is shown in FIGS. 1, 4, and 5.
This will be explained with reference to the figures.

FIG. 4 shows a specific configuration diagram of the DC/AC converter 22 of FIG. 1 and a connection diagram of the reactor 24 and transformer 25, and the following operation will be explained using the U-phase as an example. ■ phase,
Since the W phase operates in the same manner as the U phase, a description thereof will be omitted.

GTO209, GTO212 and GTO210 in Figure 4
The on/off state of the GTO 211 is controlled by a signal from the PWM control circuit 31 shown in FIG.

FIG. 5 is a diagram for explaining the on/off operation of the GTO, in which Xs is a carrier wave selected at a frequency sufficiently higher than the frequency of the AC power supply 1, es is the output signal of the current control circuit 30, This is the inverted signal of

The PWM control circuit 31 compares the input signals es and Xs,
If Xs≧es, rOJ; if Xs<es, “1”
The signal gAS of is calculated, and es and Xs are compared, and Xs
Signal g is “1” if >es, “0” if Xs≦es
Calculate Bs.

Here, the positive half cycle of the signal es is TAS, and the signal e
Let TBS be the negative half period of s.

And, in the period TAS, GTO209 and GTO in Fig. 4
212 is on/off controlled, and during the period TBS, the GT shown in Fig. 4 is controlled.
Controls on/off of O210 and GTO211.

During the period TAS, the signal gAs is input to the GTO209 and becomes "1".
" is on, and "0" is off. Signal gBS is GT
When input to O212, it is turned on when it is "1" and turned off when it is "0".

During the period TBS, the signal gAs is input to the GTO210 and "
It turns on when it is 0 and turns off when it is 1. Signal TBS is G
When input to TO211, it turns on when it is "O" and turns off when it is "1".

Now, the DC voltage of the commutation capacitor 20 is
When the voltage rises above the voltage of OA, charging current flows to the power capacitor 2OA through the diode 5, and the voltage increases. When this voltage rises above the set voltage set by the voltage setting device 26 and the voltage USV of the U-phase winding of the transformer 25 turns on the GTO 209 and GTO 212 during the TAS period, the voltage UV is output to the input side of the AC reactor 24A. . transformer 2
Since the difference voltage between the voltage USV of the U-phase winding No. 5 and the voltage UV is applied to the AC reactor 24, if UV-USV>0, the U-phase current Iu is as follows: power capacitor 20A → reactor 21 → GTO 209 x AC reactor 24A → U-phase winding 25U of transformer 25 → GTO 212 → Current flows in the closed circuit of power capacitor 2OA. At this time, the secondary power of the electric motor m2 is regenerated to the AC power supply 1. Also, when the GTO209 is turned off, the U-phase current 1u changes from the AC reactor 24A to the transformer U-phase winding 25U-+GTO212 diode 31.
0→Flows in the closed circuit of AC reactor 24A.

Now, the DC voltage of the commutation capacitor 20 is
When the voltage rises above the voltage of OA, charging current flows to the power capacitor 2OA through the diode 5, and the voltage increases. If this voltage rises above the set voltage set by the voltage setting device 26, secondary power is regenerated to the AC power supply 1 via the DC/AC converter 4 in order to suppress the rise.

Therefore, the voltage USV induced in the U-phase winding 25U of the transformer 25 is G, TO209 and GTO2 during the TAS period.
12 on and off, and GTO210 during the TBS period.
and controls the on/off of GTO211.

When GTO 209 and GTO 212 are turned on, a voltage U%' determined by the charging voltage of power capacitor 2OA is applied to the input side of AC reactor 24A.

Voltage USV induced in U-phase winding 25U of transformer 25
Note that the difference voltage between the AC reactor 24 A and the voltage UV is applied to the AC reactor 24 A. If UV - USV > 0, the U-phase current IU is as follows: Power capacitor 20 A → Reactor 21 → GTO 20
9 = AC reactor 24A-U phase winding 25U → GTO2
12→Flows in a closed circuit of power capacitor 2OA. At this time, the secondary power of the electric motor 2 is regenerated to the AC power supply 1.

Next, when GTO209 is turned off, the U-phase current IU changes from AC reactor 24A-+U-phase winding 25U→GTO212→
The current flows in a closed circuit from the diode 310 to the AC reactor 24A.

FIG. 5 shows the operating waveform when such an operation is performed 11 times. The UV dotted line in FIG. 5 shows the voltage waveform induced in the U-phase winding 25U, and UV
This is the A input voltage waveform.

Next, by turning on GTO210 and GTO211 during the TBS period, U-phase current II is changed from power capacitor 20A to reactor 21 to GTO211 to U-phase winding 2
It flows in a closed circuit of 5U-AC reactor 24A 4GTO 210→power capacitor 2OA, and at this time, the secondary power of the motor is regenerated to the AC power supply 1. Next, when the GTO 211 is turned off, the U-phase current IU flows in a closed circuit of AC reactor 24A-GTO 210 → diode 312 → U-phase winding 25U → AC reactor 24A.

As described above, since a sinusoidal current having the same phase as the voltage USV induced in the U-phase winding 25U can be supplied, the current regenerated to the AC power supply 1 is a sinusoidal wave and has a power factor of 1.

[Effects of the Invention] As explained above, according to the present invention, the secondary current of the motor can be made to flow as a sine wave with the same phase as the secondary voltage, and the secondary power can be made to flow as a sine wave with the same phase as the power supply voltage. Since the wave current can be regenerated into the AC power source, it is possible to provide a speed control device for a wound induction motor that can suppress harmonic current and reduce the capacity of the converter.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an embodiment of the present invention, FIG. 2 is a circuit diagram showing a specific embodiment of the AC/DC converter shown in FIG.
3 is a waveform diagram for explaining the operation of the PWM control shown in FIG. 2, FIG. 4 is a circuit diagram showing a specific example of the DC/AC converter shown in FIG. 1, and FIG. FIG. 6 is a waveform diagram for explaining the operation of PWM control, FIG. 6 is a characteristic diagram showing the relationship between speed and power under a square torque load, and FIG. 7 is a single-line circuit configuration diagram of conventional Servian control. 1... AC power supply, 2... Wound induction motor, 3...
・Transformer, 4...AC/DC converter, 5,5A...
Diode, 6... Speed setting device, 7... Speed detector, 8... Speed control circuit, 9... Transformer, 10...
- Multiplier, 11... Secondary current detector, 12... Secondary current control circuit, 13... PWM control circuit, 20...
Commutation capacitor, 2OA...power capacitor, 21.
...Reactor, 22...DC/AC converter, 23...
・Current detector, 24... AC reactor, 25...
Transformer, 26... Voltage setting device, 27... Voltage control circuit, 28... Transformer, 29... Multiplier, 30...
...Current control circuit, 31...PWM control circuit. Applicant's agent Patent attorney Takehiko Suzue No. 3 Figure number of transfers ('/,) to 4a Cabinet festival map

Claims (2)

[Claims] (1) A speed control device for a wound induction motor that performs speed control by regenerating secondary power of a wound induction motor whose primary winding is connected to an AC power source via a power conversion device to the AC power source, comprising: A transformer in which secondary windings are provided independently for each phase and a primary winding is connected to the secondary winding of the wound induction motor, and a secondary winding of the transformer is connected to each phase input terminal on the AC side. a commutating capacitor connected via a diode to the DC side output terminal of the connected AC/DC converter which is PWM controlled; , means for calculating a current reference signal whose phase is the same as the secondary voltage phase of the wound induction motor; The speed of a wound wire induction motor is composed of a PWM control means for PWM controlling a converter, and a DC/AC converter that receives the DC voltage of the commutating capacitor as input, converts the DC to AC, and regenerates the AC power to the AC power source. Control device. (2) A speed control device for a wound induction motor that performs speed control by regenerating secondary power of a wound induction motor whose primary winding is connected to an AC power source via a power conversion device to the AC power source, comprising: A transformer in which secondary windings are provided independently for each phase and a primary winding is connected to the secondary winding of the wound induction motor, and a secondary winding of the first transformer is connected to each phase input terminal on the AC side. a commutating capacitor connected via a first diode to a DC side output terminal of an AC/DC converter to which a winding is connected and which is subjected to PWM control; means for calculating a first current reference signal proportional to the deviation signal of the wound-type induction motor and whose phase is the same as the secondary voltage phase of the wound-type induction motor; The AC/DC converter is set to P depending on the deviation from the current detection signal.
a first PWM control means for WM control; a second transformer having secondary windings provided independently for each phase and a primary winding connected to the AC power supply; a power capacitor connected via a second diode, a DC side input terminal connected to the power capacitor via a reactor, and an AC side each phase output terminal connected to each secondary winding of the second transformer. a connected DC/AC converter, and a second current reference signal whose amplitude is proportional to a deviation signal between the voltage detection signal of the power capacitor and the voltage reference signal and whose phase is the same as the voltage phase of the AC power supply. and second PWM control means for PWM controlling the DC/AC converter according to the deviation between the second current reference signal and the regenerative current detection signal to the AC power source. Control device.