JP2012110138A - Motor drive system - Google Patents

Abstract

In a system for driving a motor in which a DC power source is connected to a neutral point of a stator winding, AC power can be output to the outside without providing a dedicated inverter.
In a motor drive system in which at least two motor drive devices each having a smoothing capacitor, an AC motor, and a power converter are connected in parallel with a smoothing capacitor as a DC link unit, neutral points of motors 40 and 50 are provided. And a DC power source 60 connected between one end of the DC link unit, a switch 12 connected between the power converter 20 and the motor 40, and the power converter 30 with the switch 12 turned off. To control the voltage of the DC link unit to a predetermined value while using the AC motor 50 as a reactor, and operate the power converter 20 to convert the DC power of the DC link unit to AC power, And a control device 70 for outputting.
[Selection] Figure 1

Description

  The present invention relates to a motor drive system for driving an AC motor connected to each power converter by a plurality of power converters connected in parallel to a DC link unit. The present invention relates to a motor drive system that can output AC power to the outside.

In a motor drive system in which a plurality of AC motors are driven by a power converter, for example, a method described in Patent Document 1 is a method for improving the efficiency of the entire system while driving each motor independently by a DC constant voltage. There is.
FIG. 5 is a configuration diagram of the motor drive system described in Patent Document 1. In FIG. In FIG. 5, 101 and 102 are inverters, 103 is a capacitor connected to the DC link unit, 201 and 202 are AC motors such as synchronous motors connected to the AC side of the inverters 101 and 102, and 104 is one motor 202. A battery 105 as a DC power source connected between the neutral point of the stator winding and the negative DC bus is a control unit.

  In the above configuration, one inverter 102 drives the motor 202 by outputting an AC voltage while boosting so that the voltage of the capacitor 103 becomes higher than the voltage of the battery 104, and the other inverter 101 performs the boost operation. Instead, the AC voltage is output and the motor 201 is driven and controlled independently of the motor 202. With this configuration, the motor input current can be reduced, and the overall efficiency of the apparatus can be improved.

  On the other hand, a conventional technique using an electric vehicle or the like as an AC power source using a motor driving device mounted on a hybrid vehicle or an electric vehicle (referred to as an electric vehicle or the like) is known. That is, an electric vehicle or the like is to be used as an emergency power source in the event of a disaster or a power source when there is no commercial power supply facility in the vicinity. Such a method of use is attracting attention as a means for increasing the commercial value of electric vehicles and the like.

As a method of outputting AC 100V from a hybrid vehicle equipped with a battery, for example, there is a method described in Patent Document 2.
FIG. 6 is a flowchart of an AC 100V output control routine described in Patent Document 2. According to Patent Document 2, as shown in FIG. 6, based on the state of an inverter that outputs AC 100V, a vehicle control system, an AC outlet, and a battery that exchanges power with a motor, AC 100V by an inverter Is determined whether or not to be output (S100 to S106, S109).
Moreover, the charge / discharge state of the battery is determined, and the output of AC 100V by the inverter is limited according to the result (S107, S108, S110, S111).
According to this prior art, it is possible to ensure good drive control of the vehicle and to output AC 100V using the power of the battery of the hybrid vehicle depending on the situation.

In Patent Document 1 described above, no means for generating AC power and outputting it to the outside is provided. However, according to Patent Document 2, AC power can be generated using a vehicle-mounted battery.
However, in Patent Document 2, it is necessary to provide an inverter exclusively for AC output, which hinders downsizing, weight reduction, and cost reduction of the system.

As a method for solving the above-described problem of Patent Document 2, for example, there are methods described in Patent Document 3 and Patent Document 4.
FIG. 7 shows the prior art described in Patent Document 3. In FIG. 7, 301 is a DC / DC converter that controls the voltage of the DC power supply 302 to a predetermined value, 311 and 312 are inverters that share a DC link unit, and MG ₁ and MG ₂ are energized and controlled by inverters 311 and 312, respectively. Motor generators MG ₁ , MG ₂ , 321 are AC outlets, ENG is an engine connected to _one motor generator MG ₁ , 400 is a control device, Q ₁ , Q ₂ , Q _{11 to} Q ₁₆ , Q _{21 to} Q ₂₆ Is a semiconductor switch constituting the DC / DC converter 301 and the inverters 311 and 312.

In this prior art, the inverter 311 controls the neutral point of the motor generator MG ₁ to a predetermined zero phase voltage, and the inverter 312 controls the U, V, and W phase arms connected to the motor generator MG _2. Thus, the voltage of the U-phase distribution line is controlled to a predetermined value, and a commercial AC voltage can be output from the AC outlet 321.
In Patent Document 4, the neutral point of the motor generator MG ₂ is connected to the AC outlet 321 like the motor generator MG _1, and the AC voltage generated between the two neutral points is output to the AC outlet 321. is doing.

JP 2002-10670 A (paragraphs [0022] to [0025], FIG. 1 etc.) JP 2002-374604 A (paragraphs [0029] to [0035], FIG. 3 etc.) Japanese Patent Laying-Open No. 2005-318682 (paragraphs [0037] to [0064], FIG. 2 etc.) JP 2006-158010 A (paragraphs [0022] to [0039], FIG. 1 and the like)

According to the prior art described in Patent Documents 3 and 4, AC power can be output from the motor drive device to the outside without providing a dedicated inverter. However, in a system in which a DC power source such as a battery is connected to the neutral point of a motor as in Patent Document 1, AC power cannot be output to the outside by the methods of Patent Documents 3 and 4.
SUMMARY OF THE INVENTION Accordingly, a problem to be solved by the present invention is to provide a motor drive system that can output AC power to the outside without providing a dedicated inverter in a system for driving an AC motor having a DC power source connected to a neutral point. It is in.

In order to solve the above-mentioned problem, a motor drive system according to claim 1 transfers power between a smoothing capacitor, an AC motor in which a stator winding is star-connected, and the smoothing capacitor and the AC motor. And a power converter in which the semiconductor switch is controlled to be turned on and off to constitute a motor drive device,
In a motor drive system in which at least two motor drive devices are connected in parallel with the smoothing capacitor as a DC link unit,
A DC power source connected between the neutral point of the stator windings of all AC motors and one end of the DC link;
A switch connected between the power converter in the first motor drive and the AC motor;
With the switch turned off, the power converter in the second motor drive device is operated and the AC motor connected to the power converter is used as a reactor while the voltage of the DC link unit is set to a predetermined value. Control means for controlling and controlling the DC power of the DC link unit to be converted into AC power by operating a power converter in the first motor driving device and outputting the AC power to the outside. It is.

According to a second aspect of the present invention, there is provided a motor drive system in which a smoothing capacitor, an AC motor in which a stator winding is star-connected, and a semiconductor switch on / off controlled so as to transfer power between the smoothing capacitor and the AC motor. And a power converter to constitute a motor driving device,
In a motor drive system in which at least two motor drive devices are connected in parallel with the smoothing capacitor as a DC link unit,
A switch connected between the power converter in the first motor drive and the AC motor;
A DC power source connected between the neutral point of the stator winding of the AC motor in the second motor driving device and one end of the DC link unit;
With the switch turned off, the power converter in the second motor drive device is operated and the AC motor connected to the power converter is used as a reactor while the voltage of the DC link unit is set to a predetermined value. Control means for controlling and controlling the DC power of the DC link unit to be converted into AC power by operating a power converter in the first motor driving device and outputting the AC power to the outside. It is.

  A motor drive system according to a third aspect is the motor drive system according to the first or second aspect, wherein the control means limits the output of each power converter in accordance with the voltage or temperature of the DC power supply. is there.

  A motor drive system according to a fourth aspect is the motor drive system according to any one of the first to third aspects, wherein a direct current is applied to a stator winding of an AC motor in the second motor drive device by the control means. The voltage of the DC link portion is controlled without causing a current to flow and generating a torque for rotating the AC motor.

According to the present invention, in a system for driving an AC motor in which a DC power source is connected to a neutral point, the power of the DC power source is converted into AC power by a power converter through a smoothing capacitor of a DC link unit. AC power can be output to the outside.
In addition, since AC power is output to the outside using a power converter for driving an AC motor, there is no need for an inverter dedicated to AC output, and the number of parts can be reduced to suppress an increase in cost. .
Furthermore, if the output of each power converter is limited according to the state of the voltage or temperature of the DC power supply such as a battery, the state of the DC power supply can be maintained satisfactorily and a DC current can be applied to the stator winding of the AC motor. By flowing, it is possible to control the voltage of the DC link unit to a predetermined value without generating rotational torque.

It is a block diagram which shows 1st Embodiment of this invention. It is operation | movement explanatory drawing of one power converter in FIG. It is operation | movement explanatory drawing of the other power converter in FIG. It is a block diagram which shows 2nd Embodiment of this invention. It is a block diagram of the prior art described in patent document 1. FIG. 10 is a flowchart of the conventional technique described in Patent Document 2. It is a block diagram of the prior art described in patent document 3. FIG.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following embodiments, a motor drive system including two motor drive devices will be described. However, the present invention is applied to a motor drive system in which three or more motor drive devices are connected in parallel at a DC link unit. Is also applicable.

First, FIG. 1 is a block diagram showing a first embodiment of the present invention, and corresponds to claim 1.
As shown in FIG. 1, the first embodiment is an anti-parallel arrangement of two AC motors (hereinafter also simply referred to as motors) 40 and 50 having stator windings connected in a star shape, and transistors and free-wheeling diodes. The power converters 20 and 30 each composed of semiconductor switches Tr _{1 to} Tr ₆ and Tr _{7 to} Tr ₁₂ each including a connection circuit, and the neutral points of the stator windings of the motors 40 and 50 and the power converters 20 and 30. A DC power source 60 such as a battery that is connected to one end of the DC link unit and supplies DC power, a smoothing capacitor 13 that constitutes the DC link unit, and a voltage detector that detects the voltage of the smoothing capacitor 13 14, a voltage detector 15 that detects the voltage of the DC power supply 60, a current detector 16 that detects the output current of the DC power supply 60, a temperature detector 17 that detects the temperature of the DC power supply 60, The switch 12 provided between the data converter 40 and the power converter 20, the output filter 11 such as an LC filter to which the output voltage of the power converter 20 is supplied, and the AC outlet 10 connected to the output filter 11 And a control device 70 that PWM-controls the power converters 20 and 30 based on the detection values V _dc , V _b , I _b , and T _b respectively output from the detectors 14, 15, 16, and 17. Has been.
Here, the smoothing capacitor 13, the power converter 20 and the motor 40 constitute the first motor driving device in the claims, and the smoothing capacitor 13, the power converter 30 and the motor 50 constitute the second motor driving device in the claims. It is composed.

Next, a method for outputting AC power using this motor drive system will be described.
The DC power of the DC power supply 60 is supplied to the smoothing capacitor 13 via the motor 50 and the freewheeling diode in the power converter 30 to charge the smoothing capacitor 13. At this time, if the stator winding of the motor 50 is regarded as a reactor, the lower arm of the power converter 30 is regarded as a switch, and the upper arm is regarded as a diode, the power converter 30 can be operated as a step-up chopper.

FIG. 2 shows the operation of the power converter 30. The power converter 30 is PWM-controlled using a zero voltage vector. When the power converter 30 outputs a zero voltage vector, the upper arm and the lower arm are simultaneously turned on / off. Here, the upper arm semiconductor switches Tr ₇ , Tr ₉ , Tr ₁₁ are collectively displayed as Tr _p , The arm semiconductor switches Tr ₈ , Tr ₁₀ , Tr ₁₂ will be collectively described as Tr _n for explanation.

2A shows the operation when Tr _n is on, FIG. 2B shows the operation when Tr _p is on, and FIG. 2C shows the voltage / current waveform in this circuit.
In the on time T _non of Tr _n , the reactor of the motor 50 stores energy from the DC power source 60 (FIG. 2A). Further, the on-time _{T pon} the Tr _p, the energy stored in the reactor of the DC power supply 60 and the motor 50, releases the smoothing capacitor 13 (Figure 2 (b)). That is, as shown in FIG. 2 (c), by turning on and off the _Tr n, Tr _p by outputting a zero voltage vector to the power converter 30, the step-up chopper for boosting the voltage _{V b} of the DC power supply 60 to the _{V dc} Can be operated as

Returning to FIG. 1, the control device 70 includes a signal V _dc from the voltage detector 14 that detects the voltage of the smoothing capacitor 13, a signal V _b from the voltage detector 15 that detects the voltage of the DC power supply 60, and a direct current. calculates the PWM pulse PWM ₂ based on the output current of the power supply 60 to the signal _{I b} from the current detector 16 for detecting the DC link part and outputs the PWM pulse PWM ₂ to the power converter 30 (the smoothing capacitor 13 ) To control the voltage. The temperature detector 17 detects overheating of the DC power supply 60 due to overload or the like and reflects it in the control of the power converters 20 and 30 as will be described later.

While the DC power of the DC link unit is controlled by the above operation of the power converter 30, the other power converter 20 turns on and off the semiconductor switches Tr _{1 to} Tr ₆ by the PWM pulse PWM ₁ from the control device 70. Converts DC power to AC power. This AC power is output to the AC outlet 10 via the output filter 11 for removing harmonics.

Here, the operation of the power converter 20 will be described.
First, the power converter 20 and the motor 40 are disconnected by turning off the switch 12 in advance so that the AC power output from the power converter 20 is not input to the motor 40.
Next, as shown in FIG. 3A, a single-phase inverter is configured using the two-phase arms (Tr _{1 to} Tr ₄ ) of the power converter 20, and the DC power of the DC link unit is converted to AC power. To do. FIG. 3B is a conceptual diagram of PWM control, and a PWM pulse can be easily generated by comparing a sine wave voltage command with a triangular wave carrier as shown in the upper part of the figure. The output line voltage V _uv (see the lower part of FIG. 3B) of the single-phase inverter controlled using this PWM pulse includes harmonics due to switching, as shown in FIGS. 2 and 3A. If the output filter 11 (LC filter here) is used, harmonic components can be removed.
By controlling the power converter 20 as described above, a sine wave AC voltage can be generated and output to the outside from the previous stage of the switch 12 in the off state.

Next, FIG. 4 is a block diagram showing a second embodiment of the present invention, and corresponds to claim 2. In the second embodiment, unlike the first embodiment, the neutral point of the motor 40 is not connected to the DC power source 60. Other configurations are the same as those of the first embodiment.
As described above, when AC power is output by the power converter 20, the switch 12 is turned off to open the stator winding of the motor 40, so whether or not the neutral point is connected to the DC power source 60. This does not affect the operation of the power converter 20.
Therefore, even with the configuration as shown in FIG. 4, the same operation as in the first embodiment is possible. However, if the neutral point of the stator winding of the motor 40 is also connected to the DC power source 60 as shown in FIG. 1, the power converter 20 outputs a zero voltage vector with the switch 12 turned on, Similar to the power converter 30, the smoothing capacitor 13 can be charged by operating the power converter 20 as a step-up chopper.

According to the third aspect of the present invention, when the voltage detector 15 and the temperature detector 17 detect a decrease in voltage or an increase in temperature of the DC power supply 60 and each detected value reaches a preset output limit value. It is desirable to control the operation of the power converters 20, 30 to limit their output. Further, when each detected value reaches a preset output stop value, the operation of the power converters 20 and 30 may be stopped.
Thereby, it is possible to prevent the deterioration or breakage of the DC power supply 60 due to overload operation or the like.

  Further, in each of the above-described embodiments, when the power converter 30 (or the power converter 20) outputs a zero voltage vector, the stator winding of each phase of the motor 50 is provided in the stator winding as described in claim 4. Since direct current flows and no rotating magnetic field is generated, no rotating torque is generated. Therefore, the voltage of the DC link unit can be controlled to a predetermined value without rotating the motor 50.

10: AC outlet 11: Output filter 12: Switch 13: Smoothing capacitor 14, 15: Voltage detector 16: Current detector 17: Temperature detector 20, 30: Power converter 40, 50: AC motor 60: DC power supply 70 : Control device Tr _{1 to} Tr ₁₂ : Semiconductor switch

Claims (4)

Motor driving by a smoothing capacitor, an AC motor in which a stator winding is star-connected, and a power converter in which a semiconductor switch is controlled to be turned on and off so as to transfer power between the smoothing capacitor and the AC motor Configure the device,
In a motor drive system in which at least two motor drive devices are connected in parallel with the smoothing capacitor as a DC link unit,
A DC power source connected between the neutral point of the stator windings of all AC motors and one end of the DC link;
A switch connected between the power converter in the first motor drive and the AC motor;
With the switch turned off, the power converter in the second motor drive device is operated and the AC motor connected to the power converter is used as a reactor while the voltage of the DC link unit is set to a predetermined value. Control means for controlling and converting the direct current power of the direct current link unit into alternating current power by operating a power converter in the first motor driving device, and outputting to the outside, and
A motor drive system comprising: Motor driving by a smoothing capacitor, an AC motor in which a stator winding is star-connected, and a power converter in which a semiconductor switch is controlled to be turned on and off so as to transfer power between the smoothing capacitor and the AC motor Configure the device,
In a motor drive system in which at least two motor drive devices are connected in parallel with the smoothing capacitor as a DC link unit,
A switch connected between the power converter in the first motor drive and the AC motor;
A DC power source connected between the neutral point of the stator winding of the AC motor in the second motor driving device and one end of the DC link unit;
With the switch turned off, the power converter in the second motor drive device is operated and the AC motor connected to the power converter is used as a reactor while the voltage of the DC link unit is set to a predetermined value. Control means for controlling and converting the direct current power of the direct current link unit into alternating current power by operating a power converter in the first motor driving device, and outputting to the outside, and
A motor drive system comprising: In the motor drive system according to claim 1 or 2,
The motor control system characterized in that the control means limits the output of each power converter according to the voltage or temperature of the DC power supply. In the motor drive system according to any one of claims 1 to 3,
The control means controls the voltage of the DC link section without causing a torque to rotate the AC motor by causing a DC current to flow through the stator winding of the AC motor in the second motor driving device. Motor drive system.

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