JP2001238455A - Multiple power converter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize regenerative operation of a load apparatus to be driven with a multiple power converter through the addition of only a small number of parts and control, without having to increase the size of the apparatus. SOLUTION: A multiple power converter comprises a multiple power converter 3 of single phase through serial connection of a plurality units of inverter 4 and AC side, and drives a three-phase induction motor 6 with an three-phase AC outputted from connections of a plurality of multiple power converter. A unit inverter 5 of multiple power converter of each phase is provided with a damping resistance unit 51 to process the regenerative energy from a motor, a motor application voltage calculator, a regeneration on/off discriminator, a switching signal generator, a regenerative torque current zero setter, and a regenerative torque current instruction generator, are provided as a controller 8. A terminal voltage of the motor is measured or estimated simultaneously, when deceleration of motor is started when decelerating or stopping of the operation of rotating motor is conducted. When the terminal voltage is lowered from the preset value, the motor is broke regeneratively and stopped.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multiplex power converter having a regenerative function, and more particularly to a regenerative technique for driving an AC motor using the same.

[0002]

2. Description of the Related Art Existing high-voltage AC motors (3.3 kV,
(6.6 kV or the like) by using an inverter to make the speed variable, energy saving can be realized. Therefore, a multiple inverter system has been put into practical use as a high voltage motor driving technology. Since it is difficult to increase the breakdown voltage of the semiconductor element constituting the inverter, a low-voltage inverter is multiplexed to cope with this (for example, Japanese Patent Application Laid-Open No. 10-337042).
Further, by multiplexing low-voltage inverters, distortion of the output voltage of the inverter is reduced, and insulation deterioration due to harmonics of the motor winding is prevented. The high-voltage motor is mainly used for driving a fan, a pump, and the like, and generally does not require a regenerative operation in many cases. Therefore, the DC power supply of each unit inverter constituting the multiplex inverter is constituted by a diode rectifier and a smoothing capacitor.

[0003]

In a conventional multiplex inverter for driving a high-voltage motor, electric power from the high-voltage motor cannot be regenerated to a power source, so that the motor cannot be quickly decelerated. Particularly, in the case of a load with a large inertia such as a fan, it is difficult to suddenly decelerate. If a power regeneration function is added, regeneration is possible, but there are problems in terms of the size of the device and cost. Since multiple inverters require variable speeds of existing motors, it is desirable to avoid increasing the size of the device as much as possible. Also, in order to expand the applications of the high-voltage motor, a device that can apply regenerative braking is desired.

An object of the present invention is to realize a regenerative operation of a load device driven by a multiplex power conversion device by adding and controlling a few components without increasing the size of the device.

[0005]

In order to solve the above-mentioned problems, a multiplex power converter comprising a plurality of multiplex power converters comprising a plurality of unit inverters, or a three-phase inverter and the plurality of multiplex power converters are connected. In a multiplex power converter connected with a multiplex power converter, a braking resistor that consumes regenerative power is added to a DC section of at least one unit inverter or to a DC section of a three-phase inverter, and a three-phase load device is provided. When the regenerative operation is performed, regenerative energy is consumed by using the braking resistor. Here, when decelerating or stopping the rotating induction motor, the current flowing through the secondary winding of the induction motor is controlled to substantially zero, and the exciting current is controlled to a specific value other than zero. In addition, when the rotating induction motor is decelerated or stopped, the terminal voltage of the induction motor is measured or estimated at the same time as the start of deceleration of the induction motor, and when the terminal voltage falls below a predetermined value, the induction motor is deactivated. Is regeneratively braked to stop the induction motor.
Also, when the rotating induction motor is decelerated or stopped, the excitation current of the induction motor is gradually reduced at the same time as the deceleration of the induction motor is started, and at the same time, the terminal voltage of the induction motor is measured or estimated. When the value falls below the set predetermined value, the induction motor is regeneratively braked to stop the induction motor. Also, when the rotating induction motor is decelerated or stopped, the excitation current of the induction motor is gradually reduced at the same time as the deceleration of the induction motor is started, and at the same time, the terminal voltage of the induction motor is measured or estimated. When the induction motor falls below a predetermined value, the induction motor is regeneratively braked. At the same time, the exciting current is controlled so that the terminal voltage is kept near the predetermined value, and the induction motor is stopped. Also, when the rotating induction motor is decelerated or stopped, the excitation current of the induction motor is gradually reduced at the same time as the deceleration of the induction motor is started, and at the same time, the terminal voltage of the induction motor is measured or estimated. When the induction motor falls below a predetermined value, the induction motor is regeneratively braked, and at the same time, the exciting current is controlled so that the terminal voltage is maintained at the predetermined value. To stop.

[0006]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a multiplex power converter according to a first embodiment of the present invention. This embodiment is a three-phase multiplex power converter configured by multiplexing four unit inverters per phase. In FIG. 1, a part number 1 is a three-phase AC power supply, 2 is an input transformer, 3 is a multiplex power converter that outputs each phase voltage, 4 is a unit inverter that outputs a single-phase AC, 41 is a diode rectifier, 42 Is a smoothing capacitor, 43 is a single-phase full-bridge inverter, 5 is a unit inverter to which a braking resistor 51 ″ is added, and 51 is a switch that turns on the switch 51 ′ when the DC voltage of the unit inverter 5 becomes excessive, thereby consuming power. Braking resistance unit,
6 is a load device represented by an induction motor, 7 is a current detector for detecting a load current, and 8 is a controller for controlling the multiplex power converter.

The operation principle of this embodiment will be described. Power is supplied from the three-phase AC power supply 1 to each of the unit inverters 4 and 5 via the transformer 2. The transformer 2 is inserted for step-down of the power supply and insulation between the unit inverters. In the unit inverters 4 and 5, as shown in FIGS.
Outputs a single-phase alternating current. In the unit inverter 5, a braking resistor unit 51 is added to the DC section, and when the DC voltage (smoothing capacitor voltage) becomes excessive, power is consumed by the braking resistor 51 ″. Next, the regenerative operation in FIG. When the induction motor 6 rotates at a high speed and a high voltage is applied to the motor, the regeneration is not performed because the regeneration of only the unit inverter 5 is impossible with respect to the pressure resistance. In the state where the terminal voltage of the motor is low and the motor can be driven only by the unit inverter 5, regeneration is performed in the range shown in FIG.
Since 1 is added, regeneration is possible when the motor is driven at a voltage of about 1/4 or less of the motor rating. At the time of regeneration, all output voltages of the unit inverter 4 are set to zero, the switch 51 'is turned on, and only the unit inverter 5 is switched to perform regeneration. In many applications of high-voltage induction motors, such as fans, pumps, and the like, have a squared torque load, and these loads consume power in proportion to the cube of the speed. That is, since the load increases as the motor speed increases, regenerative energy hardly occurs even in a high speed region even if the deceleration time is shortened (regenerative power and load power are canceled). Conversely, since the load decreases as the speed decreases, it is necessary to increase the deceleration time in a device having no regenerative ability. However, in the multiplex power converter according to the present embodiment, since regeneration in the low speed range can be realized as described above, there is no need to lengthen the deceleration time, and deceleration / stop can be performed quickly. In addition, although a system using a power regeneration converter instead of the diode rectifier in each unit inverter has been proposed, in the present embodiment, braking can be easily applied at a lower cost, and an increase in the size of the device can be avoided. it can.

FIG. 4 shows a second embodiment of the present invention.
This embodiment is a multiplex power converter configured by combining three single-phase unit inverters and one three-phase inverter. In FIG. 4, part numbers 1-4, 41, 4
2 and 51 are the same as those in the embodiment of FIG. 5E is a three-phase inverter unit that outputs a three-phase AC, and 52 is a three-phase full-bridge inverter.

The operation principle of this embodiment will be described. The configuration of the multiplex power converter according to the present embodiment is such that the unit inverter 4E is provided with a three-phase inverter 5E at the neutral point.
Are connected in series. Therefore, only the three-phase inverter unit 5E has a DC power supply common to three phases. The braking resistor unit 51 is provided in the three-phase inverter unit 5E, and is connected to the braking resistor unit 51.
Can be commonly used for the three phases. Next, the regeneration operation in FIG. 4 will be described. The regenerative operation is the same as that of the embodiment of FIG. 1, and the electric motor rotates at a low speed and performs the regeneration within a range where the electric motor can be driven only by the three-phase inverter unit 5E. In the present embodiment, since the braking resistance unit 51 can be made common to the three phases, the size of the device can be further reduced as compared with the embodiment of FIG. Note that the present invention can be similarly applied to a case where the three-phase inverter unit is, for example, a three-level inverter.

FIG. 5 shows an equivalent circuit for one phase of the induction motor 6. The equivalent circuit is a primary resistor R1, a leakage inductor L
σ, the secondary resistance R2 ′, and the excitation inductance M ′. In FIG. 5, a voltage applied by an inverter (including a multiple power converter) is V1, and a current flowing at that time is I1, and I1 is divided into an exciting current I0 and a torque current (secondary current) I2. The torque generated by the induction motor is generated in proportion to the secondary current I2. Therefore, in order to reduce the speed of the induction motor, the generated torque may be reduced by reducing I2. However, if I2 is a negative value,
Regeneration operation is performed, and electric power is regenerated from the induction motor to the inverter. Therefore, if the inverter does not have a regenerative function, controlling I2 to zero is the fastest way to decelerate the motor. To do so, the controller 8 may control the voltage and current applied to the induction motor in a fixed relationship. For example, in FIG. 5, to make I2 zero, I1 =
It can be seen that it is sufficient to control to I0, and to control it so that the phase of the current I1 is delayed by 90 ° with respect to the phase of the voltage V1 (R1 is ignored). As a conventional deceleration method when the inverter has no regenerative ability, there are a method of (1) lowering the speed at a constant rate, and a method of (2) suppressing the inverter (turning off all the switching elements) and naturally decelerating the inverter. . In (1), there is a possibility that I2 is flowing at a positive value, so that the deceleration time is wasted. In (2), by suppressing the inverter, the exciting current I0
However, the processing when the suppression is canceled again becomes complicated (for example, when it is desired to decelerate from high-speed operation and maintain rotation at low speed). In this case, it is necessary to start the exciting current from the identification (detection) of the rotation speed of the motor. On the other hand, according to the embodiment of the present invention, since the exciting current I0 is maintained and only the torque current I2 is controlled to zero, the above problem is solved, and a quick deceleration can be obtained.

FIG. 6 shows an example of the configuration of the controller 8 of the embodiment shown in FIGS. In FIG. 6, part number 9
Is a speed command generator that outputs a speed command ωr * of the induction motor 6, 10 is an adder (subtractor) that adds (subtracts) a signal, 11 is a speed controller that controls the speed of the induction motor,
12 is a magnetic flux command generator for outputting a magnetic flux command Φ * of the induction motor, and 13 is an excitation current command Id * based on the magnetic flux command Φ *.
And 14 are current commands Id * and Iq *
A voltage command calculator for calculating voltages vd * and vq * applied to the induction motor based on the following equation; 15 is a current controller for controlling the torque current Iq of the induction motor; 16 is current control for controlling the excitation current Id of the induction motor Container, 17 is a rotating coordinate axis (dq
The voltage commands vd * and vq * on the coordinate axes) are converted into three-phase voltage commands Vu
*, Vv *, Vw *, a coordinate converter 18 for converting the phase currents Iu, Iv into currents on the dq axes, 1
9 is a slip calculator for calculating slip ωs of the induction motor,
20 is an integrator for calculating the magnetic flux axis phase θ by integrating the primary angular frequency ω1 of the induction motor, 21 is a three-phase voltage command Vu *,
A multiplex PWM modulator for generating a pulse for switching the multiplex converter based on Vv * and Vw *, 22 is a speed detector / estimator for detecting or estimating the rotational speed ωr of the induction motor, and 23 is applied to the induction motor. | V1 | calculator that calculates the magnitude of the voltage | V1 | that is being used, 24 is a regenerative propriety discriminator that determines whether | V1 | is greater than a set value Vrg and outputs a regenerative signal F2, 25 A switching signal generator 26 that receives the deceleration / stop signal F1 of the induction motor and the signal of F2 and generates a switching signal F3, and switches SW1 and SW2 that switch the torque current command Iq * according to the value of F3.
Reference numeral 7 denotes a setter that outputs zero, and reference numeral 28 denotes a regenerative torque current command generator that generates a torque current command Iqrg * during regeneration.

Next, the operation principle of the controller 8 will be described. During normal operation, a torque current command Iq * is calculated by the speed controller 11 according to the difference between the speed command ωr * and the actual speed ωr, and the current controller 15 for Iq and the voltage command calculator via the switch (SW1) 26. It is sent to 14. Normally, the switch (SW1) is connected to the state of “0”. The excitation current command Id * is calculated based on the magnetic flux command Φ *, and is sent to the current controller 16 for Id and the voltage command calculator 14. In the voltage command calculator 14, Id,
The voltage applied to the induction motor is calculated from the interference component on the dq axes of Iq and the speed electromotive voltage. On the other hand, the current controllers 15, 1
Numeral 6 is provided to improve the current response in the transient state and to correct the deviation due to the constant error of the electric motor. The correction is calculated and added to vd * and vq *. The slip frequency ωs of the induction motor is calculated by the slip calculator 19 from the torque current command Iq * and added to the actual speed ωr to obtain the primary angular frequency ω1. ω1 is integrated by the integrator 20 to obtain the rotational coordinate axis phase θ of the electric motor. Based on this θ, the phase current detection values Iu and Iv are coordinate-transformed to obtain actual measured values IdFB and IqFB of the excitation current and the torque current. Further, based on θ, voltage commands vd *, vq * are converted to values Vu *,
The coordinates are converted into Vv * and Vw *. The multiplex PWM modulator 21 calculates a switching pulse signal to be given to each unit inverter based on the values of Vu *, Vv *, and Vw *.
The above is the basic control block of the induction motor, which has a configuration based on the conventional vector control. The configuration characterized by the present invention includes a | V1 | arithmetic unit 23, a regeneration enable / disable discriminator 24, a switching signal generator 25, and a switch (SW1).
26, a zero setter 27, and a regenerative torque current command generator 28.

Next, the operation during deceleration, which is a characteristic part of the present invention, will be described with reference to FIGS. FIG. 7 shows the signal movement from the start of deceleration to the stop of the induction motor. First, when decelerating / stopping the induction motor, a deceleration signal F1 is input from outside. Normally, F1 = 0, but at deceleration time t0, F1 = 1 is set (FIG. 7). The switching signal generator 25 sets the switching signal F3 to “1” in response to F1 = 1 (normally “0”). As a result, the switch (SW1) 26 is switched to “1”, and I
q * is moved from the output of the speed controller 11 to Iq * = 0. When the torque current command Iq * becomes zero, the generated torque of the induction motor disappears, and the induction motor decelerates. During this time, no regenerative operation is performed, and the induction motor naturally decelerates (FIG. 7).
Speed ωr). On the other hand, the | V1 | calculator 23 calculates the absolute value | V1 | of the terminal voltage of the induction motor using voltage commands (vd *, vq * or Vu *, Vv *, Vw *) inside the controller. The calculation of the absolute value | V1 | is as shown in (Equation 1) when the phase voltage command is used. | V1 | = (√2 / 3) (√Vu * ² + Vv * ² + Vw * ² ) (Equation 1) Also, when a voltage command on the dq axes is used, (Equation 2) is obtained. | V1 | = (1 / √3) (√vd * ² + vq * ² ) (Equation 2) It should be noted that there is no problem even if the above calculation is performed using the detected value of the terminal voltage instead of the voltage command. In the regeneration enable / disable discriminator 24,
| V1 | is compared with a preset value Vrg, and | V1 | <
At time t1 when Vrg is reached, the regeneration signal F2 is changed from "0" to "1". In the multiplex power converter of the embodiment of FIG. 1, the braking resistor unit 51 is connected to one of the four unit inverters, so that Vrg is set to about １ ／ of the rated voltage of the motor. It is good. In the switching signal generator 25, when F1 = 1 and F2 = 1, the value of the switching signal F3 is set to “2” and given to the switch (SW1). Switch (SW1) 2
In step 6, it is switched to "2" and Iq * is set to the regenerative current
g * (Iqrg * <0).

The state from deceleration to regeneration will be further described with reference to FIG. In FIG. 7, deceleration is started at time t0, and Iq is controlled to zero immediately after the start of deceleration (switch (S
W1) 26 switches to “1”). As a result, the motor naturally decelerates, and the terminal voltage | V1 | of the motor also decreases in proportion to the speed. At the time point t1 when | V1 | becomes smaller than Vrg, it is determined that regeneration is possible and the switch (SW1) 26
Is switched to “2”, and Iq is a predetermined regenerative current value Iqr.
g * and the motor is braked. At this time,
In the multiple power converter, only the unit inverter to which the regenerative braking unit 51 is added is operated, and the output of the other unit inverters is set to zero. The motor is quickly decelerated and stopped by the regenerative braking. As described above, it is possible to realize an induction motor driving device that quickly decelerates and stops the induction motor by the controller 8 of FIG.

FIG. 8 shows another configuration example of the controller 8 of the embodiment shown in FIGS. In FIG. 8, part numbers 9, 10, 12 to 15, 17 to 21, and 23 to 28 are
It is the same as the same number in FIG. FIG. 8 shows a controller 8A based on speed sensorless vector control. 6, the d-axis current controller 1
6, the speed detector / estimator 22 has been deleted.
The q-axis current controller 15 is not used during normal operation,
Use only during deceleration and regeneration. At this time, the output of the q-axis current controller 15 is added to the primary angular frequency command ω1 of the induction motor as a frequency correction signal Δω1. The deceleration / regeneration operation of the controller 8A of FIG. 8 is the same as that of the controller 8 of FIG. Simultaneously with the start of the deceleration, the switch (SW1) 26 and the switch (SW2) 26 are switched to “1”, and the primary angular frequency ω1 is changed so that the torque current Iq becomes zero. As a result, the motor naturally decelerates and | V1 | <Vrg
At the time t1 when it is determined that regenerative braking is possible, regenerative braking is started. When | V1 | <Vrg, SW1 and SW2 are switched to “2”, and Iq is controlled to be the set value Iqrg * at the time of regeneration. As described above, the present invention can be applied to the speed sensorless vector control.

FIG. 9 shows a configuration example of the magnetic flux command generator 12 in FIGS. 6 and 8. In FIG. 9, part number 1
0, 12, and 27 are the same as the same numbers in FIGS. 121 is a switch SW3 for switching a switch according to the value of the deceleration signal F1, and 122 is a time constant T
The integrator 123 integrates the input at a, and a limiter 123 sets the minimum value of the magnetic flux command to Φmin. Next, the operation of the magnetic flux command generator 12B of FIG. 9 will be described. Φ * is the rated magnetic flux of the induction motor and is normally output as it is as Φ **. The motor starts to decelerate, and the deceleration signal F1 is "1"
, The switch (SW3) 121 switches to “1”. The integrator 122 integrates and outputs Φ *, and the subtractor 10 subtracts from the original Φ *. Therefore, Φ ** gradually decreases simultaneously with the start of deceleration. However, the limiter 12
The minimum value Φmin is set by 3 so that it does not become zero.

Referring to FIG. 10, magnetic flux command generator 1 shown in FIG.
The operation when 2B is applied to the controller 8 in FIG. 6 or the controller 8A in FIG. 8 will be described. In FIG. 10, time t0
Starts deceleration. Since the magnetic flux command generator 12B of FIG. 9 is used, the magnetic flux command Φ ** decreases simultaneously with the deceleration. Since the magnetic flux decreases, the terminal voltage | V1 |
, The voltage drops faster than Vrg in a short time. At time t1 when | V1 | <Vrg, regeneration is determined to be “permitted”, regeneration is performed as in FIG. 6 or FIG. 8, and the motor is stopped. Lower limit value Φmin of Φ ** and integrator 1
If the time constant Ta of 22 is set small, the voltage can be reduced more quickly. However, since the regenerative torque is reduced by the decrease in the magnetic flux, the regenerative braking time may be longer. The magnetic flux command generator 12B is effective when the inertia of the load is large and | V1 | does not readily decrease.

FIG. 11 shows another example of the configuration of the magnetic flux command generator 12 in FIGS. 11, the component numbers 10, 12, 27, 121, 122 are the same as the same numbers in FIGS. 6, 8, and 9. 1
23C sets the magnitude of the magnetic flux command to a minimum value Φmin and a maximum value Φ
*, A limiter 124 for inverting the sign of the magnetic flux command Φ *, a hysteresis comparator 125 for comparing the magnitude of | V1 | with two set values Vrg0 and Vrg1, and outputting a magnetized signal F4. It is. Next, FIG.
The operation of the first magnetic flux command generator 12C will be described. Φ
* Is the rated value of the motor and is normally output as it is as Φ **. When the motor starts decelerating and the deceleration signal F1 becomes "1", the switch (SW3) 121 switches to "1". The integrator 122 integrates and outputs Φ *,
Subtractor 10 subtracts from the original Φ *. Therefore, Φ *
* Gradually decreases as soon as deceleration starts. However, the minimum value Φmin is set by the limiter 123 so that it does not become zero. Due to the deceleration and the demagnetization, the terminal voltage of the motor rapidly decreases. When | V1 | becomes Vrg or less, regenerative braking is started. The regeneration further reduces the speed of the motor, and the terminal voltage further decreases. At this time,
The hysteresis comparator 125 sets the magnetized signal F4 to "1" when | V1 | becomes smaller than the preset value Vrg0. When F4 became "1",
The switch (SW4) 121 is switched to “1”, and the sign of Φ * input to the integrator 122 is inverted. As a result, the magnetic flux once decreased rises again. When the magnetic flux increases, | V1 | rises again. The hysteresis comparator 125 sets F4 to "0" again when | V1 | becomes larger than Vrg1. Here, the hysteresis comparator 125 suppresses the rattling of the switching in the vicinity of Vrg. These operations are repeated, and as a result, the magnetic flux once reduced is restored to the original value (rated value). Note that, in the limiter 123C, a limiter value is also provided for the upper limit value in order to prevent Φ ** from being increased to the rated magnetic flux Φ * or more.

The operation when the magnetic flux command generator 12C of FIG. 11 is applied to the controller 8 of FIG. 6 or the controller 8A of FIG. 8 will be described with reference to FIG. At time t0, deceleration is started, and at the same time as deceleration, the magnetic flux command Φ ** decreases. Since the magnetic flux decreases, the motor terminal voltage | V1 |
It becomes below. At time t1 when | V1 | <Vrg, it is determined that regeneration is possible, regeneration is started, and the speed of the motor further decreases. At this time, the hysteresis comparator 125 shown in FIG. 11 operates to increase the magnetic flux command Φ **, and re-magnetize the magnetic flux once reduced. Even after the start of regeneration | V1 |
Is kept constant for a while. The magnetic flux command generator 12C
Since the magnetic flux at the time of regeneration is larger than that of the magnetic flux command generator 12B of FIG. 9, a larger regenerative torque is obtained, and the deceleration time from the start of regeneration is further shortened.

FIG. 13 shows an example of the configuration of the regenerative torque current command generator 28 shown in FIGS. The regenerative torque current command generator 28D of FIG. 13 is applied to the controller 8 of FIG. 6 or the controller 8A of FIG. 8 to which the magnetic flux command generator 12C of FIG. 11 is applied. In FIG. 13, the part number 281
Is a function generator that inputs the magnetic flux command Φ ** in FIG. 11 and calculates the regenerative torque current command Iqrg * according to the magnitude. In the regenerative torque current command generator 28 shown in FIGS. 6 and 8, the regenerative torque current is fixed at a constant value.
8D makes it possible to change the torque current during regeneration according to the motor magnetic flux. According to FIG. 10, since the motor magnetic flux is weakened at the start of regeneration, a sufficient regenerative torque cannot be obtained. Also, since the magnetic flux is weakened, if an attempt is made to flow an excessively large regenerative torque current, there is a possibility that the control system becomes unstable due to the occurrence of axial misalignment or the like. Therefore, when the magnetic flux is reduced, an excessively large regenerative current cannot flow. However, the magnetic flux command generator 12C of FIG. 11 has a function of gradually increasing the magnetic flux command Φ **, which has been weakened once, at the same time as the start of regeneration, and returning to the rated magnetic flux again. As shown in FIG. 14, the regenerative torque current I
By increasing q (Iq <0), a larger regenerative torque can be stably generated. As mentioned above,
By changing Iqrg * as a function of the magnetic flux command Φ **, the regenerative braking time can be further reduced.

In the above-described embodiments of the present invention, an example is described in which the number of unit inverters per phase is four, but the present invention is applicable to any number of stages. Further, even if a regenerative braking unit is added to a plurality of unit inverters, the deceleration / regeneration method of the present invention can be applied. Also, the deceleration / stop method according to the present invention is shown in FIG.
The description has been given on the assumption that the multiplex power converter has the configuration of FIG. 4, but the present invention can be similarly applied to the multiplex power converter of the configuration of FIG. In the deceleration method of the present invention, the torque current is controlled to zero at the same time as the start of deceleration, and the natural deceleration is performed. However, there is no problem if the motor is decelerated at a constant deceleration rate during this time. Further, in the regenerative system of the present invention, all the regenerative energy is processed by the braking resistor. However, the present invention may be applied to a system in which a power regenerative converter is added instead of the braking resistor unit to regenerate energy to the power source. All the regeneration methods described as above can be applied.

[0022]

As described above, according to the present invention,
A braking resistance unit is provided for some of the unit inverters that make up the multiplex power converter, and the torque current and the motor magnetic flux are appropriately controlled, so that regenerative braking can be effectively realized without increasing the size of the device. Thus, the motor can be quickly decelerated and stopped. In addition, since a braking resistor for regeneration is connected to a part of the unit inverter constituting the multiplex inverter, the number of resistors can be reduced, and an increase in the size of the device can be avoided. In addition, since a three-phase inverter is used as a part of the multiplex inverter and a braking resistor for regeneration is connected to the DC part, it is not necessary to add a braking resistor for each of the three phases. realizable. Also, when the induction motor is driven by multiple inverters, the secondary current of the induction motor is controlled to zero, so that the torque generated by the motor can be reduced to zero. It is possible to quickly decelerate by the torque. When an induction motor is driven by a multiplex inverter, a part of the unit inverter constituting the multiplex inverter is provided with a regenerative function, and the terminal voltage of the motor is detected simultaneously with the start of deceleration of the motor. Waits for a voltage level at which the motor can be regenerated, and regenerates the electric power of the motor at the time when the motor can be regenerated, so that the rotating motor can be quickly decelerated. In addition, at the same time as deceleration, the exciting current of the induction motor is reduced, thereby reducing the terminal voltage earlier and shortening the waiting time until regenerative operation is possible, and regenerating the electric power of the motor. can do. At the same time as the regenerative operation is started, the exciting current of the induction motor is controlled, the motor terminal voltage is controlled to a value as large as possible within a regenerable range, and the regenerative power is increased as much as possible. it can. In addition, since the regenerative power is changed according to the magnitude of the exciting current during regeneration, the regenerative torque can be increased as much as possible, and the motor can be decelerated more quickly. Further, by applying the above-described means to a multiplex power conversion device constituted by a plurality of single-phase unit inverters and at least one three-phase inverter capable of processing regenerative power, further miniaturization and reduction of deceleration time are achieved. Shortening is achieved.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a multiplex power conversion device according to a first embodiment of the present invention.

FIG. 2 is a configuration diagram of a unit inverter according to the present invention.

FIG. 3 is a configuration diagram of a unit inverter with a braking resistance unit according to the present invention.

FIG. 4 is a configuration diagram according to a second embodiment of the present invention.

FIG. 5 is an equivalent circuit model for one phase of an induction motor.

FIG. 6 is a configuration diagram of a controller according to the present invention.

FIG. 7 is an operation waveform diagram of the present invention.

FIG. 8 is another configuration diagram of the controller of the present invention.

FIG. 9 is a configuration diagram of a magnetic flux command generator according to the present invention.

FIG. 10 is an operation waveform diagram of the present invention.

FIG. 11 is another configuration diagram of the magnetic flux command generator of the present invention.

FIG. 12 is an operation waveform diagram of the present invention.

FIG. 13 is a configuration diagram of a regenerative torque current generator according to the present invention.

FIG. 14 is an operation waveform diagram of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Three-phase alternating current power supply, 2 ... Input transformer, 3 ... Power converter for one phase, 4 ... Unit inverter, 5 ... Unit inverter, 6 ... Load device such as induction motor, 7 ... Current detector, 8 ... Controller, 41 ... Diode rectifier, 42 ... Smoothing capacitor, 43 ... Single-phase full-bridge inverter, 51
... Brake resistance unit 12 ... Flux command generator, 23 ... | V1 | Calculator, 24 ...
Regeneration enable / disable discriminator, 25: switching signal generator, 26: switch (SW1) (SW2), 27: zero setting device, 28:
Regenerative torque current command generator 12B, 12C ... magnetic flux command generator, 28D ... regenerative torque current command generator

Continuing from the front page (72) Inventor Koichiro Nagata 7-1-1, Omika-cho, Hitachi City, Ibaraki Prefecture Inside Hitachi Research Laboratory, Hitachi, Ltd. (72) Inventor Shigetoshi Okamatsu 5-2-1 Omika-cho, Hitachi City, Ibaraki Prefecture Hitachi, Ltd., Omika Works

Claims (9)

[Claims] 1. A unit inverter for inputting DC power and converting it to single-phase AC, and a plurality of unit inverters are prepared, and the AC side is connected in series to constitute a single-phase multiplex power converter, In a multiplex power converter that drives a multi-phase load device by connecting a plurality of multiplex power converters, regenerative power is supplied to a DC unit of the unit inverter for at least one unit inverter in the multiplex power converter of each phase. A multiplex power conversion device, comprising: adding a braking resistor for consuming power, and consuming regenerative energy using the braking resistor when the polyphase load device performs a regenerative operation. 2. A three-phase inverter for inputting DC power and converting to three-phase AC, a unit inverter for inputting DC power and converting to single-phase AC, and connecting a plurality of AC units of the unit inverter in series. And a multiplex power converter that drives the three-phase load device by connecting the multiplex power converter to the output of each phase of the three-phase inverter. A braking resistor that consumes regenerative power is added to the DC section of the inverter,
A multiplex power converter, wherein when the three-phase load device performs a regenerative operation, regenerative energy is consumed using the braking resistor. 3. The multiplex power converter according to claim 1, wherein the current flowing through the secondary winding of the induction motor is reduced to substantially zero when the rotating induction motor is decelerated or stopped. A multiplex power converter that controls the excitation current to a specific value other than zero. 4. A unit inverter for inputting DC power and converting it to single-phase AC, and a plurality of unit inverters are prepared, and the AC side is connected in series to constitute a single-phase multiplex power converter, In a multiplex power converter that drives a three-phase induction motor with a three-phase alternating current output by connecting a plurality of the multiplex power converters, the induction motor is connected to at least one unit inverter in the multiplex power converter of each phase. Means for processing the regenerative energy of the motor, and when decelerating or stopping the rotating induction motor, the terminal voltage of the induction motor is measured or estimated at the same time as the deceleration of the induction motor is started, and the terminal voltage is determined in advance. A multiplex power converter, wherein the induction motor is regeneratively braked when the voltage falls below a predetermined value, and the induction motor is stopped. 5. The multiplex power converter according to claim 4, wherein when the rotating induction motor is decelerated or stopped, the exciting current of the induction motor is gradually reduced at the same time as the deceleration of the induction motor is started. At the same time, the terminal voltage of the induction motor is measured or estimated, and when the terminal voltage falls below a predetermined value, the induction motor is regeneratively braked to stop the induction motor. apparatus. 6. The multiplex power converter according to claim 4, wherein, when decelerating or stopping the rotating induction motor, the exciting current of the induction motor is gradually reduced at the same time as the deceleration of the induction motor is started, Simultaneously, the terminal voltage of the induction motor is measured or estimated, and when the terminal voltage falls below a predetermined value set in advance, the induction motor is regeneratively braked, and at the same time, the terminal voltage is kept near the predetermined value. And controlling said exciting current so as to stop said induction motor. 7. The multiplex power converter according to claim 4, wherein, when decelerating or stopping the rotating induction motor, the exciting current of the induction motor is gradually reduced at the same time as the deceleration of the induction motor is started, At the same time, the terminal voltage of the induction motor is measured or estimated, and when the terminal voltage falls below a predetermined value set in advance, the induction motor is regeneratively braked, so that the terminal voltage is maintained at the predetermined value at the same time. A multiplex power converter, comprising: controlling the exciting current; changing regenerative torque as a function of the exciting current value; and stopping the induction motor. 8. The multiplex power converter according to claim 4, wherein said multiplex power converter comprises a combination of a plurality of said unit inverters and one three-phase inverter, A multiplex power converter, comprising: a phase inverter for processing regenerative power of the induction motor. 9. The secondary winding of the induction motor according to claim 4, wherein the induction motor is decelerated until the terminal voltage reaches the predetermined value. Control the current flowing through to substantially zero, and
A multiple power converter, wherein an exciting current is controlled to a specific value other than zero.