JP4140992B2 - Electric motor drive power converter and motor controller - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a power conversion device for driving a motor capable of regeneration processing and a motor control device including the device.
[0002]
[Prior art]
In an application field where the load motor is in a regenerative state, in order to regenerate regenerative power to the AC power supply side, the power necessary for driving is supplied from the AC power supply to the motor drive device during powering of the motor, and the motor side during regeneration It is known to use a power converter for driving an electric motor configured to regenerate regenerative power from an AC power source to an AC power source. Generally, this type of electric power converter for driving an electric motor includes a converter bridge circuit having the same configuration as an inverter bridge circuit constituting an inverter circuit for driving an electric motor, and a plurality of the converter bridge circuits Regenerative power is regenerated to the AC power supply side by PWM (pulse width modulation) control of the semiconductor switching element. For example, an example of this type of motor drive power converter is shown in FIG. 4 of Japanese Patent Laid-Open No. 8-205560.
[0003]
[Problems to be solved by the invention]
Conventionally, a motor drive power conversion device capable of performing power regeneration processing for each motor having different capacities has been individually designed and manufactured. However, the number of electric motors used in application fields that require power regeneration processing is not necessarily large, and there is a problem that the price of the electric power converter for driving the motor becomes high because the number of manufactured motors is small.
[0004]
In addition, the power characteristics of the semiconductor switching elements constituting the converter / bridge circuit are limited, and there is a problem in that this type of motor drive power conversion device cannot be applied to a motor having a certain capacity.
[0005]
An object of the present invention is to provide a motor-driven power conversion device and a motor control device that are easy to design and inexpensive.
[0006]
Another object of the present invention is to provide a motor-converting power converter and motor controller having a desired capacity using a plurality of converter units.
[0007]
Another object of the present invention is to provide a motor drive power conversion device and a motor control device having a desired capacity using a plurality of types of converter units having different capacities.
[0008]
Still another object of the present invention is to provide a motor-driven power conversion device and a motor control device that can easily and surely obtain a desired capacity by using a plurality of converter units.
[0009]
[Means for Solving the Problems]
The present invention provides a power conversion device for driving a motor configured to supply electric power necessary for driving from an AC power source to a driving device of the motor during powering of the motor, and to regenerate regenerative power from the motor side to the AC power source during regeneration. Subject to improvement.
[0010]
In the motor-driven power conversion device of the present invention, a bridge circuit (converter / bridge circuit) configured by bridge-connecting a plurality of semiconductor switching elements and a plurality of diodes connected in antiparallel to these semiconductor switching elements. When powering the motor, the AC power supplied from the AC power source is converted to DC power, and during regeneration, the DC power regenerated from the motor side is converted to AC power and regenerated to the AC power source to be regenerated to the AC power source. A bridge circuit (converter bridge circuit) of a plurality of converter units including a control circuit for controlling the semiconductor switching element is connected in parallel between the AC power supply and the output unit. Usually, the bridge circuit is connected to an AC power source via a reactor.
[0011]
Here, in general, the converter / bridge circuit has the same configuration as the inverter / bridge circuit that constitutes the inverter circuit of the motor drive device. Specifically, in the case of three phases, a three-phase bridge circuit is configured by semiconductor switching elements such as six transistor elements, and a diode is connected in antiparallel to each semiconductor switching element. And the conduction | electrical_connection of the semiconductor switching element of each converter unit is controlled by PWM (pulse width modulation) control.
[0012]
The number of converter units connected in parallel is determined according to the capacity of the motor to be driven. For example, when the capacity of the converter unit is 5 kW and the capacity of the electric motor is 20 kW, bridge circuits of four converter units are connected in parallel. When the capacity of the converter unit is 30 kW and the capacity of the electric motor is 50 kW, the bridge circuits of the two converter units are connected in parallel.
[0013]
Therefore, in the present invention, a control circuit for a plurality of converter units connected in parallel is configured so that the plurality of converter units have a current (current flowing from the output unit during power running and current flowing into the output unit during regeneration) according to the capacity of each converter unit. It is configured to share. For example, when a bridge circuit of n converter units (n is a positive integer) having substantially the same capacity is connected in parallel, the current flowing from the output unit during power running is I, and the current flowing into the output unit during regeneration is Assuming I, the control circuit is configured so that an I / n current flows through each converter unit.
[0014]
As in the present invention, when a bridge circuit of a plurality of converter units is connected in parallel to configure a power converter having a desired capacity, the number and capacity of converter units connected in parallel according to the capacity of the motor are substantially reduced. Therefore, it is possible to obtain a power conversion device for driving a motor having a required capacity. Therefore, it is possible to simply and inexpensively provide a motor-driven power conversion device corresponding to various types of electric motors simply by preparing converter units having a plurality of types of capacities in advance as general-purpose products.
[0015]
The control circuit is provided with a voltage control loop system that outputs a current command for making the voltage of the output unit constant. When a voltage control loop system is provided for each converter unit, if the characteristics of the voltage control loop system provided for each converter unit are different, the value of the current command processed by each converter unit will be different. The system becomes unstable. Therefore, it is preferable to provide one voltage control loop system that outputs a current command for making the voltage of the output unit constant to a plurality of converter units. In this case, each of the control circuits of the plurality of converter units is configured so that each bridge circuit is configured to share a current at a ratio corresponding to each capacity with a current command from one voltage control loop system as an input. What is necessary is just to comprise so that the several semiconductor switching element to perform may be controlled. In this way, since a common current command is input to each converter unit, there is no inconvenience such as system instability.
[0016]
Specifically, the control circuit of each converter unit may be provided with current command level changing means for changing at least the level of the current command input. As described above, for example, when a bridge circuit of n converter units (n is a positive integer) having substantially the same capacity is connected in parallel, the current flowing from the output unit during power running and the output unit flows into the output unit during regeneration. If the current is I, the level of the current command level changing means of each control circuit is set so that a current of I / n flows through the bridge circuit of each converter unit.
[0017]
In some cases, a converter unit can be configured with a single converter unit. To deal with such a case, a current command for making the output voltage constant is output to the control circuit of the converter unit. A voltage control loop system for changing the current command level and a current command level changing means for changing the level of the current command. When a plurality of converter units are connected in parallel, only one voltage control loop system included in the control circuit of one converter unit among the plurality of converter units is connected to the output unit. On that basis, the current command level changing means of each control circuit of the plurality of converter units is input to the current command output from one voltage control loop system connected to the output unit, and the ratio according to each capacity. Set the level to share the current. The current command level changing means can be easily configured by, for example, an adjustable voltage dividing circuit or a gain adjusting circuit. Therefore, even if the current command level changing means is provided in each converter unit, one converter unit The price is not so high. Therefore, in consideration of the productivity of the converter unit and the assemblability of the power converter, it is preferable to provide each converter unit with a voltage control loop system and a current command level changing means.
[0018]
An electric motor control device to which the present invention is directed is an inverter circuit comprising an inverter bridge circuit in which a plurality of semiconductor switching elements and a plurality of diodes connected in antiparallel to these semiconductor switching elements are bridge-connected. The motor drive device including the motor and the motor driven by the motor drive device are configured to supply power from the AC power source to the motor drive device during power running, and to regenerate regenerative power from the motor drive device side to the AC power source during regeneration. An electric motor driving power conversion device and a capacitor connected in parallel to the output unit of the electric motor driving power conversion device are provided. Also in the motor control device of the present invention, the above-described motor drive power conversion device may be used.
[0019]
When the capacity of the motor is large enough to require an energizing current that is equal to or higher than the rated current of the semiconductor switching element (for example, 80 kW or more), the inverter circuit cannot be configured with a simple bridge circuit. In such a case, the inverter circuit may be configured by connecting a plurality of inverter circuits in parallel.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an example of an embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic circuit diagram of an example of an embodiment in which a motor-driven power conversion device of the present invention is applied to a motor control device used for controlling a three-phase induction motor 5. In this embodiment, two converter units CU1 are provided between the three-phase AC power source 1 and the output unit (the input unit of the inverter bridge circuit 4 or both ends of the smoothing capacitor 6 constituting a part of the motor driving device). The converter bridge circuits 3 and 13 of CU2 are connected in parallel, and the two converter units CU1 and CU2 share current according to their capacities.
[0021]
In FIG. 1, reference numeral 1 denotes a three-phase AC power source, and reference numeral 2 denotes a reactor that is arranged between each phase from the AC power source 1 and the input of the three-phase converter / bridge circuit 3 and exhibits a current adjusting function. The bridge circuit 3 is configured by bridge-connecting six insulated gate bipolar transistors 3T, each called a IGBT, in which diodes 3D are connected in parallel to a collector-emitter circuit. In addition, each diode 3D is arrange | positioned with the polarity which does not flow a regenerative current. A semiconductor switching element called IPM in which a protection circuit is attached to the IGBT can be used in place of the transistor 3T.
[0022]
The output part of the converter / bridge circuit 3 is connected to an inverter / bridge circuit 4 of a three-phase inverter circuit used as an electric motor driving device for supplying driving power to the three-phase induction motor 5 and a smoothing capacitor 6 made of an electrolytic capacitor. And connected in parallel to the output terminal of the three-phase converter / bridge circuit 13. The three-phase inverter circuit applies a control signal to the bridge circuit 4 and the insulated gate bipolar transistors 4T, which are formed by bridge-connecting six insulated gate bipolar transistors 4T having diodes 4D connected in parallel to the collector-emitter circuit. An inverter driving device (not shown) that outputs AC power of a predetermined frequency from the bridge circuit 4 is configured.
[0023]
The DC voltage appearing at both ends of the smoothing capacitor 6 is differentiated from the output voltage input from the command control unit (not shown) at the addition point SM1, that is, the DC voltage command for commanding the voltage across the terminals of the smoothing capacitor 6. The voltage is input to a proportional-integral controller or PI controller 7. The PI controller 7 outputs a current command for instructing the value of the current supplied from the output part of the converter / bridge circuit 3 to the inverter / bridge circuit 4 necessary for making the output voltage a predetermined voltage based on the difference voltage. Output. The PI controller 7 calculates the voltage between the terminals of the smoothing capacitor 6 (the voltage of the output unit) from the difference voltage between the voltage between the terminals of the smoothing capacitor 6 (the input terminal of the inverter / bridge circuit 4) and the reference voltage (DC voltage command). ) Becomes equal to or higher than the reference voltage, it is determined that the regenerative state has been entered. The PI controller 7 determines whether the charge control or the discharge control is based on whether the differential voltage is equal to or higher than the reference voltage, and outputs a current command for powering control and a current command for regenerative control. . Therefore, the current command is reversed between power running and regeneration. In other words, a current command that keeps the voltage across the smoothing capacitor 6 constant is output during power running and regeneration, but a current command that raises the voltage across the smoothing capacitor 6 to a predetermined voltage during power running. During regeneration, the current command is such that the voltage across the smoothing capacitor 6 is lowered to a predetermined voltage.
[0024]
In this example, the feedback line from the smoothing capacitor 6 to the adding point SM1 and the voltage at the output section (voltage between the terminals of the smoothing capacitor 6) from the adding point SM1 and the PI controller 7 are made constant. One voltage control loop system that outputs a current command is configured. This current command is also input to the control circuit 19 of the second converter unit CU2.
[0025]
Reference numeral 9 denotes a control circuit of the first converter unit CU1. The control circuit 9 includes three-phase current control systems 9 u to 9 w for controlling the current of each phase flowing through the converter / bridge circuit 3. FIG. 1 shows only the configuration of one current control system 9u for controlling one phase. 9A is a current command level changing means. The current command level changing means 9A is for changing the level of the current command input from the PI controller 7 so as to share the current at a ratio corresponding to the capacity of the converter unit. Specifically, the current command level changing means 9A can be constituted by a voltage dividing circuit. For example, when the capacities of the first and second converter units CU1 and CU2 are equal, the current command level changing means 9A outputs a current command in which the level of the current command input from the PI controller 7 is halved. Output. In this case, the first converter unit CU1 shares a half current, and the second converter unit CU2 also shares a half current. When the ratio of the capacities of the first and second converter units CU1 and CU2 is in a one-to-two relationship, the current command level changing means 9A sets the level of the current command input from the PI controller 7 to 1. The current command set to / 3 is output. In this case, the first converter unit CU1 shares 1/3 of the current, and the second converter unit CU2 shares 2/3 of the current. In the above example, the current is shared in a relationship that is completely proportional to the capacity of the converter unit, but the present invention is not limited to this. For example, when the capacity ratio of two converter units is 1: 1, the current sharing may be 1: 1. In short, sharing current according to capacity in the present invention means sharing current to the extent that the capacity of each converter unit is not exceeded. Therefore, when two converter units having the same capacity are connected in parallel, if the capacity is within an allowable range, one converter unit shares 1/3 of the current and the other converter unit shares 2/3. The current may be shared. However, when considering the life of each converter unit, when two converter units having the same capacity are connected in parallel, one converter unit shares a half current and the other converter unit also has a 1 / Of course, it is preferable to share the two currents. Note that this current sharing is the same both when the electric motor is powered and regenerated.
[0026]
The current command level changing means 9A may be provided for each of the current control systems 9u to 9w for three phases, but one current command level changing means is provided for the current control systems 9u to 9w for three phases. It may be provided and shared by the current control systems 9u to 9w of the respective phases. The current command whose level has been changed by the current command level changing unit 9A is input to the multiplier 9B. The multiplier 9B multiplies the current command whose level has been changed by the power supply voltage phase of the corresponding phase, so that the current command becomes a sine wave current. In order to multiply the power supply voltage phase, the power supply voltage is directly input from the power supply line between the three-phase AC power supply 1 and the converter / bridge circuit 3 to the multipliers 9B of the current control systems 9u to 9w of the respective phases. In FIG. 1, for simplification of illustration, the power supply voltages for three phases are illustrated as being input to one current control system 9u. Are respectively input to the multipliers 9B of the current control systems 9u to 9w.
[0027]
The power supply current (AC current) of the corresponding phase is subtracted from the sine wave current as a result of multiplication of the level-changed current command output from the multiplier 9B and the power supply voltage phase at the second addition point SM2. Is done. Corresponding phase power supply currents are input from current detectors 8 formed of current transformers or the like provided in power supply lines between the three-phase AC power supply 1 and the converter / bridge circuit 3. In FIG. 1, for simplification of illustration, power supply currents for three phases are illustrated as being input to one current control system 9u. Are respectively input to the second addition points SM2 of the current control systems 9u to 9w. Eventually, the power source current is fed back with respect to the sine wave current, and the difference between the sine wave current and the corresponding phase power source current is input to the current regulator 9C.
[0028]
The current regulator 9C outputs a converter voltage command that brings the charging current and discharging current (regenerative current) close to the current command value that is a sine wave current. The converter voltage command output from the current regulator 9C is a signal proportional to the difference signal between the AC current detected by the current detector 8 and the current command (sine wave current). In one current control system 9u, a pulse width modulation control signal generation circuit, that is, PWM 9D, is connected to the six insulated gate bipolar transistors 3T of the converter bridge circuit 3 based on the converter voltage command output from the current regulator 9C. A conduction control signal for controlling the conduction angle of the two insulated gate bipolar transistors 3T... In a period in which the value of the converter voltage command is large, the conduction angle of the corresponding transistor is large, and when the value of the converter voltage command is small, the conduction angle of the corresponding transistor is small. In the other current control systems 9v and 9w, the same control is performed on the two insulated gate bipolar transistors 3T.
[0029]
The second converter unit CU2 is configured in the same manner as the first converter unit CU1. Therefore, description of each member is abbreviate | omitted by attaching | subjecting the code | symbol of the number which added 10 to the code | symbol attached | subjected to the member which comprises 1st converter unit CU1 to 2nd converter unit CU2. The second converter unit CU2 is different from the first converter unit CU1 in that there is no first addition point SM1 and PI controller 7 constituting one voltage control system loop, and the first converter unit CU2 The current command output from the PI controller 7 of the unit CU1 is input to the current command level changing means 19A of each current control system 19u to 19w. Although not shown in FIG. 1, in this example, since the units having the same structure are used as the first and second converter units CU1 and CU2, voltage control is actually applied to the second converter unit CU2. A configuration corresponding to the first addition point for configuring the loop system and the PI controller is included. However, in this example, since these members are not used, these members are omitted from FIG. When a voltage control loop system is provided for each converter unit, the current command value processed by each converter unit differs if the characteristics of the voltage control loop system provided for each converter unit are different. The system becomes unstable. In this example, therefore, one voltage control loop system that outputs a current command for making the voltage of the output section (the voltage across the terminals of the smoothing capacitor 6) constant for the two converter units is provided. is there.
[0030]
In this example, since the units having the same structure and the same capacity are used as the first and second converter units CU1 and CU2, the current control systems 9u to 9w and 19u of the control circuits 9 and 19 of the converter units are used. The current command level changing means 9A and 19A provided at .about.19w are set so as to output a current command in which the level of the current command output from the PI controller 7 is reduced to 1/2. Therefore, the drive current supplied to the inverter / bridge circuit 4 when the motor 5 is controlled to power and the regenerative current that flows when the motor 5 regenerates the regenerative power to the AC power source 1 are the first and second converter units CU1 and Each CU2 is assigned 1/2.
[0031]
In the motor-driven power conversion device used in this example, when the motor 5 is powered, an alternating current synchronized with the power supply voltage of the alternating current power supply 1 flows through the transistors 3T, 13T, and the diodes 3D, 13D, and rectifies, It operates so as to keep the voltage of the smoothing capacitor 6 constant. When the electric motor 5 is actually powered, the voltage across the smoothing capacitor 6 decreases. Therefore, the charging current flows from the three-phase AC power source 1 through the converter / bridge circuits 3 and 13 to the smoothing capacitor 6, and the smoothing capacitor 6 is charged. The voltage of the smoothing capacitor 6 is kept constant. When the electric motor 5 is regenerated, the smoothing capacitor 6 is charged by the regenerative power, and the terminal voltage of the smoothing capacitor 6 rises. From the smoothing capacitor 6, the converter bridge circuit 3 of the first and second converter units CU1 and CU2 and 13 is discharged to the three-phase AC power source 1, and an AC current whose phase is synchronized with the power source current is regenerated to the three-phase AC power source 1. Also at this time, control is performed so as to keep the voltage of the smoothing capacitor 6 constant.
[0032]
In the above example, two converter units are connected in parallel. However, according to the capacity of the motor and the capacity of the converter unit to be used, more converter units are connected in parallel to provide a power converter for driving the motor. May be configured. When the capacity of the motor increases, not only the bridge circuits of a plurality of converter units are connected in parallel, but also the bridge circuits of a plurality of inverter / bridge circuits 4 may be connected in parallel. When the bridge circuits are connected in parallel as described above, even if there is a limit on the capacity of the semiconductor switching element to be used, it is possible to drive and control an electric motor having a capacity exceeding the limit.
[0033]
In the above example, a hysteresis comparator can be used in place of the PI controller 7 constituting a part of the DC voltage control loop. The hysteresis comparator has an advantage that the digital processing in the control circuits 9 and 19 becomes easy when the hysteresis comparator is used because the input is analog and the output is digital.
[0034]
【The invention's effect】
As in the present invention, when a bridge circuit of a plurality of converter units is connected in parallel to configure a power converter having a desired capacity, the number and capacity of converter units connected in parallel according to the capacity of the motor are substantially reduced. Therefore, it is possible to obtain a power conversion device for driving a motor having a required capacity. Therefore, there is an advantage that it is possible to easily and inexpensively provide a power conversion device for driving a motor corresponding to a motor having various capacities only by preparing a converter unit having a plurality of capacities as a general-purpose product in advance.
[Brief description of the drawings]
FIG. 1 is a schematic circuit diagram of an example of an embodiment in which a power conversion device for driving a motor according to the present invention is applied to a motor control device used for controlling a three-phase induction motor 5;
[Explanation of symbols]
CU1 and CU2 First and second converter units 1 Three-phase AC power source 2, 12 Reactor 3, 13 Converter bridge circuit 4, Inverter bridge circuit 5, Three-phase induction motor 6 Smoothing capacitor 7 PI controller 8 Current detector 9 , 19 Control circuits 9A, 19A Current command level changing means 9B, 19B Multipliers 9C, 19C Current regulators 9D, 19D Pulse width modulation control signal generation circuit (PWM)

Claims (3)

An electric power conversion device for driving an electric motor configured to supply electric power necessary for driving from an AC power source to the electric motor during powering of the electric motor and to regenerate electric power from the electric motor side to the AC power source during regeneration. ,
A plurality of semiconductor switching elements and a plurality of diodes connected in reverse parallel to the semiconductor switching elements, and a bridge circuit configured to be connected to the AC power supply via a reactor; and a power running of the electric motor Sometimes the AC power supplied from the AC power source is converted to DC power, and at the time of regeneration, the DC power regenerated from the motor side is converted to AC power and regenerated to the AC power source to be regenerated to the AC power source. A bridge circuit of a plurality of converter units comprising a control circuit that performs PWM control of conduction of the semiconductor switching element is connected in parallel between the AC power supply and the output unit,
The control circuit of the plurality of converter units includes a voltage control loop system that outputs a current command for making the voltage of the output unit constant, and a current command level changing unit that changes the level of the current command. And
Only one voltage control loop system included in the control circuit of one converter unit of the plurality of converter units is connected to the output unit,
The current command level changing means of the control circuit of each of the plurality of converter units has the current command output from one voltage control loop system connected to the output unit as an input to each capacity. A power conversion device for driving an electric motor, characterized in that a level is set so as to share a current at a corresponding ratio. An electric motor drive device including an inverter circuit composed of an inverter bridge circuit configured by bridge-connecting a plurality of semiconductor switching elements and a plurality of diodes connected in reverse parallel to the semiconductor switching elements;
For driving an electric motor configured to supply electric power from an AC power source to the electric motor driving device during powering of the electric motor driven by the electric motor driving device and to regenerate electric power from the electric motor driving device side to the AC power source during regeneration. A power converter,
An electric motor control device comprising a capacitor connected in parallel to the output unit of the electric motor driving power conversion device,
The electric power drive device for driving an electric motor is similar to the inverter bridge circuit in which a plurality of semiconductor switching elements and a plurality of diodes connected in reverse parallel to the semiconductor switching elements are bridge-connected to constitute the inverter circuit. The converter bridge circuit configured as described above and the AC power supplied from the AC power source when the motor is powered are converted to DC power, and the DC power regenerated from the motor side is converted to AC power during regeneration The converter bridge circuit of a plurality of converter units comprising a control circuit that PWM-controls the plurality of semiconductor switching elements of the converter bridge circuit so as to regenerate to an AC power source, the AC power source, the output unit, Having a configuration connected in parallel between
The control circuits of each of the plurality of converter units are configured such that the plurality of converter units share current according to their respective capacities ,
The control circuit of the plurality of converter units includes a voltage control loop system that outputs a current command for making the voltage of the output unit constant, and a current command level changing unit that changes the level of the current command. And
Only one voltage control loop system included in the control circuit of one converter unit of the plurality of converter units is connected to the output unit,
The current command level changing means of the control circuit of each of the plurality of converter units has the current command output from one voltage control loop system connected to the output unit as an input to each capacity. An electric motor control device , characterized in that a level is set so as to share current at a ratio corresponding to the electric current . The motor control device according to claim 2 , wherein the motor driving device has a configuration in which a plurality of inverter circuits are connected in parallel.

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