JP2010239765A - Motor drive device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem of a motor drive device which drives a motor by directly switching an AC voltage, in which a switching element included in a converter has various characteristics and there are various driving conditions, so that motor driving with switching loss, conduction loss, drive loss, and the like suppressed in response to conditions cannot be easily achieved. <P>SOLUTION: At least one of a voltage detection unit 5 which detects characteristics of a switching element included in a converter 2 as well as a voltage applied to the converter 2, a phase detection unit 6 for detecting an AC power supply phase, a current detection unit 7 for detecting a motor current, a rotational speed detection unit 8 for detecting a rotational speed of a motor, and a carrier frequency variable part 9 for varying a PWM carrier frequency is provided. Further, a signal output switching part 10 is provided which switches the number of PWM outputs from a signal output unit 4 based on the motor drive condition detected by any of them, for simply achieving high efficiency of the entire device. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a motor driving device that can directly switch an AC voltage from an AC power source to drive a three-phase motor at a variable speed.

  Conventionally, this type of motor drive apparatus realizes motor drive by a PWM signal modulated by carrier comparison for turning on and off a switching element provided in a converter unit so as to prevent a power supply short circuit and a load release. In this case, the same number of PWM signals as the number of gate terminals are input to the gate terminal for inputting the ON / OFF signal of the switching element (see Non-Patent Documents 1 and 2).

  7 and 8 show a typical switching element configuration and a PWM signal input to each gate terminal.

  As shown in FIG. 8, a PWM signal modulated by carrier comparison so as not to cause a power supply short circuit and a load release is input to the gate terminal of each switching element.

  Further, as a simpler commutation method, there is a method of inputting an always-on signal to the gate terminal of the switching element in a state where the switching element may be on or off at the time of commutation (see Patent Document 1). In this method, effects such as improvement of voltage utilization rate and reduction of output voltage error can be expected by simplifying the commutation period corresponding to dead time.

FIG. 9 shows typical signals input to each gate terminal, and the commutation pattern is simplified by inputting the always-on signal to the gate terminal of the switching element in the freewheeling diode mode. ing.
Japanese Patent Laid-Open No. 2005-210805 Sakurai, Takeshita: “3-step commutation method of matrix converter”, 2007 IEEJ National Conference on Industrial Applications, 1-14, pp. 219-222 (2007) Practical application of direct AC power conversion circuit and application technology research technical committee edition: “Technology trend and application of matrix converter”, IEEJ Technical Report, No. 1111, March 2008, pp. 17

  In general, various types of devices (for example, combinations of unidirectional elements such as IGBT and RB-IGBT and bidirectional elements such as SiC and GaN) are used as switching elements provided in this type of converter section. In addition, there are various motor driving conditions. In accordance with these conditions, motor driving that suppresses switching loss of the switching element, conduction loss and drive loss for driving the signal output unit in the converter unit that is a loss when driving the motor is performed. There was a problem that it could not be easily realized.

  The present invention solves the above-described conventional problems, and motor drive that can easily suppress loss during motor drive by switching the number of PWM outputs according to the characteristics of the switching element provided in the converter unit and the motor drive conditions. An object is to provide an apparatus.

In order to solve the above-described conventional problems, the motor driving device of the present invention includes an AC power supply and a switching element capable of bidirectionally controlling the AC power supply output in a bidirectional manner. As a signal output from the signal output unit in a motor drive device including a converter unit that drives a motor with an alternating current output of a variable frequency and a signal output unit that outputs a signal for turning on and off the switching element of the converter unit. A signal output switching unit that switches between a PWM signal modulated by carrier comparison and an output fixed signal that maintains an on / off state during a plurality of carrier periods is provided.

  Thereby, the loss at the time of motor drive can be easily suppressed by switching the number of PWM outputs by the characteristic of the switching element with which a converter part is equipped, and motor drive conditions.

  The motor driving device of the present invention can easily suppress loss during motor driving by performing motor driving with a PWM output pattern according to the situation.

1st invention is provided with the alternating current power supply and the switching element which can carry out current control of this alternating current power supply bidirectionally, and the converter part which drives a motor by the alternating current output of the variable voltage and the variable frequency obtained by switching bidirectionally directly And a motor drive device including a signal output unit that outputs a signal for turning on and off the switching element of the converter unit,
The converter unit includes a signal output switching unit that switches between a PWM signal modulated by carrier comparison as a signal output from the signal output unit and an output fixed signal that maintains an on / off state during a plurality of carrier periods. PWM pattern output according to the characteristics of the switching element used for the motor can be made possible, and loss (particularly drive loss) during motor driving can be suppressed.

  According to a second aspect of the present invention, in the motor drive device according to the first aspect of the present invention, the motor drive device includes a voltage detection unit that detects an AC voltage input to the converter unit, and a PWM signal generated by the signal output switching unit based on a detection result of the voltage detection unit. By switching the number of outputs, loss (especially switching loss) during motor driving can be suppressed by the PWM output pattern corresponding to the voltage applied to the converter.

  According to a third aspect of the present invention, in the motor drive device according to the first aspect of the present invention, the motor drive device includes a phase detection unit that detects a voltage phase of the AC voltage input to the converter unit, and the signal output switching unit is detected based on a detection result of the phase detection unit. By switching the number of outputs of the PWM signal, loss (particularly switching loss) at the time of motor driving can be suppressed by the PWM output corresponding to the AC power supply phase applied to the converter.

  According to a fourth aspect of the present invention, in the motor drive device according to the first aspect of the present invention, the motor drive device includes a current detection unit that detects the motor current, and switches the number of PWM signal outputs by the signal output switching unit according to a detection result of the current detection unit. Thus, the loss (particularly switching loss) at the time of driving the motor can be suppressed by the PWM output corresponding to the motor current flowing through the converter.

  According to a fifth aspect of the present invention, in the motor drive device according to the first aspect of the present invention, the motor drive device includes a rotation speed detection unit that detects the drive rotation speed of the motor, and the PWM signal generated by the signal output switching unit is detected by the detection result of the rotation speed detection unit. By switching the number of outputs, it is possible to achieve both reduction in loss during motor driving and control performance necessary for motor driving.

According to a sixth aspect of the present invention, in the motor drive device according to the first aspect of the present invention, the motor drive device includes a carrier frequency variable unit that varies a carrier frequency for modulating the PWM output from the signal output unit. By switching the number of outputs of the PWM signal, loss (particularly switching loss) at the time of motor driving can be suppressed by PWM output corresponding to the carrier frequency.

  According to a seventh aspect of the present invention, in the motor drive device according to any one of the first to sixth aspects, the signal output switching unit switches an output signal in which the switching element operates in a freewheeling diode mode according to a signal from the signal output unit. By performing the above, loss (especially drive loss) at the time of driving the motor can be suppressed.

  According to an eighth aspect of the present invention, in the motor drive device according to any one of the first to seventh aspects, the bidirectional switching element included in the converter unit is composed of GaN having at least one of a normally-off type and a double gate type. As a result, it is possible to reduce conduction loss in the converter, increase efficiency by reducing switching loss due to high-speed switching, and improve device reliability.

  According to a ninth aspect of the present invention, there is provided an apparatus for directly switching an AC voltage to drive a motor by providing the air conditioner with the motor driving apparatus according to any one of the first to eighth aspects of the invention. Can be realized.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the present invention is not limited to the embodiments.

(Embodiment 1)
1 and 2 are configuration diagrams of a motor driving device according to an embodiment of the present invention.

  The motor drive apparatus of FIGS. 1 and 2 is supplied with electric power from an AC power source 1 and directly converts the supplied AC voltage into an AC output of a desired variable voltage and variable frequency by the converter unit 2 to drive the motor 3. The converter unit 2 includes a switching element (QRU to QTW in the case of a three-phase AC power supply input, QRU to QSW in the case of a three-phase AC power supply input) capable of bidirectionally switching the current, and the switching element has a gate terminal (three In the case of phase AC power supply input, ON / OFF is controlled by a signal from the signal output unit 4 for RU1, RU2 to TW1, TW2, and in the case of single phase AC power supply input RU1, RU2, SW1, SW2. Furthermore, a voltage detection unit 5 that detects a voltage value of the AC power supply 1, a phase detection unit 6 that detects a voltage phase of the AC power supply 1, a current detection unit 7 that detects a motor current flowing through the motor 3, and At least one of a rotation speed detection unit 8 that detects the drive rotation number of the motor 3 and a carrier frequency variable unit 9 that varies the carrier frequency of the PWM signal output from the signal output unit 4 is provided. A signal output switching unit 10 for switching the PWM signal output from the signal output unit 4 is provided.

  Here, the signal output switching unit 10 includes a voltage detection unit 5 that detects a voltage value of the AC power supply 1, a phase detection unit 6 that detects a voltage phase of the AC power supply 1, and a motor current flowing through the motor 3. At least one of a current detection unit 7 to detect, a rotation number detection unit 8 to detect the drive rotation number of the motor 3, and a carrier frequency variable unit 9 to vary the carrier frequency of the PWM signal output from the signal output unit 4. The PWM signal output from the signal output unit 4 is switched according to any detected value.

  About the motor drive device comprised as mentioned above, the operation | movement and an effect | action are demonstrated below.

  First, the operation of the switching element of the converter unit 2 by the signal output unit 4 will be described.

FIG. 3 shows a configuration of a typical bidirectional switching element provided in the converter unit 2. FIGS. 3A, 3B, and 3C are modeled on a combination of two IGBTs that are unidirectional switching elements, a combination of two reverse blocking IGBTs, and a double gate type GaN. The switching control by the gate terminals G1 and G2 is equivalent.

  FIG. 4 is an equivalent circuit of the double gate type GaN switching element Q, and Table 1 shows the operation state in each mode.

  In Table 1, “1” represents on and “0” off, and the operating state of the switching element Q is shown at the bottom. When an off signal is input to both G1 and G2, no current flows in both directions. When an ON signal is input to both G1 and G2, current can flow in both directions. When an ON signal is input to G1 and an OFF signal is input to G2, a current can flow only in the downward direction. When an OFF signal is input to G1 and an ON signal is input to G2, the current can only flow upward. it can.

  FIG. 5 shows the relationship between the gate signal of such a switching element, the voltage applied to the switching element, and the current flowing through the switching element. Tp, Ton, Tdon, and Tdoff in the figure are the carrier period of the PWM signal inputted to the gate terminal of the switching element, the on period inputted to the gate terminal of the switching element, the delay time until the switching element is turned on, The delay time until the switching element is turned off is shown. Thus, when the switching element is turned on / off, a loss as indicated by the hatched portion occurs.

  In addition to the conduction loss due to the on-resistance, the loss related to the switching element, in the case of using GaN for the switching element, is for driving the signal output unit 4 while the switching element is held in the on state. Drive loss occurs.

  Next, switching of the switching element drive signal from the signal output unit 4 by the signal output switching unit 10 will be described.

  Here, a pattern for outputting a PWM signal modulated by carrier comparison of the same number as the number of gate terminals of the switching element is A, and a pattern for outputting a signal including an output fixed signal that is kept on / off for a plurality of carrier periods. B.

  First, switching based on the detection result of the voltage detection unit 5 will be described. The voltage detection unit 5 detects a PWM output pattern B for suppressing a surge voltage generated by an output voltage change when the voltage value is equal to or higher than a predetermined voltage value V1, and detects a PWM output pattern A and a voltage for suppressing a drive loss accompanying an increase in the PWM ON period when the voltage is less than V1. By switching the PWM output pattern based on the detection result by the unit 5, the performance at the time of driving the motor is secured and the loss is reduced.

Further, the switching based on the detection result of the phase detection unit 6 is performed when the phase between the zero crosses of the AC power supply 1 (power supply half cycle) is 0 <θ <π. ) To switch the PWM output pattern as follows. First, FIG. 6 shows an input voltage waveform and a motor current waveform to the converter unit 2 when the AC power source 1 is a single-phase AC power source. As shown in FIG. 6, when the phase range is θ1 ≦ θ ≦ θ2, the voltage applied to the switching element and the flowing current increase. That is, since the area of the shaded portion in FIG. 5 increases and the switching loss increases, switching to the PWM output pattern B suppresses the switching loss and suppresses the surge voltage generated due to the output voltage change. Further, when θ <θ1 and θ> θ2, the output is switched to the PWM output pattern A in order to suppress drive loss accompanying an increase in the PWM ON period.

  Next, switching by the detection result of the current detection unit 7 is switched to the PWM output pattern A by the current detection unit 7 to suppress drive loss during the ON period in the PWM output when the current value is equal to or greater than I1, and when less than I1, the switching is performed at the time of switching. Switch to PWM output pattern B to suppress switching loss.

  Next, switching according to the detection result of the rotation speed detection unit 8 switches the PWM output pattern as follows according to predetermined rotation speeds rps1 and rps2 (0 <rps1 <rps2) with respect to the motor rotation speed rps. First, when starting from a motor stopped state or during high-speed rotation, a higher torque is required. Therefore, at a rotational speed rps <rps1, rps> rps2, it is driven by a PWM pattern B that has a high voltage utilization rate and can output a higher torque. When the rotational speed is rps1 ≦ rps ≦ rps2, the PWM output pattern A is switched to realize high-efficiency driving with suppressed drive loss.

  Next, in the switching by the carrier frequency, the total area of the hatched portion in FIG. 5 per unit time increases and the switching loss increases at a predetermined carrier frequency fc1 or more with respect to the carrier frequency fc varied by the carrier frequency variable unit 9. Therefore, switching to the PWM pattern B is performed to suppress the switching loss, and when the carrier frequency is less than fc1, the switching to the PWM output pattern A is performed in order to realize high-efficiency driving with suppressed drive loss.

  In addition, when switching according to the characteristics of the switching element (device), if an IGBT, RB-IGBT, or the like that is more affected by switching speed or operating resistance loss (switching loss, conduction loss) than drive loss is used as the switching element, PWM output When pattern B is set and GaN, etc., which has a high switching speed and low operating resistance, is used as a switching element, low loss motor drive that matches the characteristics of the switching element used is achieved by setting PWM output pattern A it can.

  As described above, in the present embodiment, by providing the signal output switching unit 10 that switches the number of PWM outputs from the signal output unit 4 according to the characteristics of the switching elements provided in the converter unit 2 and the motor driving conditions, High efficiency can be easily realized.

    As described above, since the motor drive device according to the present invention can perform PWM output corresponding to the characteristics of the switching elements to be used and various motor drive conditions, the motor drive device includes a compressor (motor) such as an air conditioner. Applicable to all devices.

The block block diagram of the motor drive device in embodiment of this invention The block block diagram of the motor drive device in embodiment of this invention AC switching element model diagram Equivalent circuit diagram of AC switching element Waveform diagram of each part in switching element Waveform diagram of each part in the embodiment of the present invention AC switching element connection diagram Schematic showing the flow of motor startup in a conventional motor drive device Schematic showing the flow of motor startup in a conventional motor drive device

DESCRIPTION OF SYMBOLS 1 AC power supply 2 Converter part 3 Motor 4 Signal output part 5 Voltage detection part 6 Phase detection part 7 Current detection part 8 Rotation speed detection part 9 Carrier frequency variable part 10 Signal switching part

Claims (9)

An AC power supply and a switching element capable of bidirectionally controlling the AC power supply output bidirectionally, and a converter unit for driving a motor by an AC output of variable voltage and variable frequency obtained by direct bidirectional switching; In the motor drive device including a signal output unit that outputs a signal for turning on and off the switching element,
A signal output switching unit that switches between a PWM signal modulated by carrier comparison as a signal output from the signal output unit and an output fixed signal that maintains an on / off state during a plurality of carrier periods is provided. Motor drive device. The motor according to claim 1, further comprising a voltage detection unit that detects an AC voltage input to the converter unit, wherein the number of PWM signals output by the signal output switching unit is switched according to a detection result of the voltage detection unit. Drive device. The phase detection part which detects the voltage phase of the alternating voltage input into the said converter part is provided, The output number of the PWM signal by the said signal output switching part is switched by the detection result of the said phase detection part, The motor drive device described. The motor drive device according to claim 1, further comprising: a current detection unit that detects the motor current, wherein the number of PWM signal outputs by the signal output switching unit is switched based on a detection result of the current detection unit. 2. The motor drive according to claim 1, further comprising: a rotation number detection unit that detects a drive rotation number of the motor, wherein the output number of the PWM signal by the signal output switching unit is switched based on a detection result of the rotation number detection unit. apparatus. The carrier frequency variable part which changes the carrier frequency which modulates PWM output from the said signal output part, The output number of the PWM signal by the said signal output switch part is switched by this carrier frequency, The signal output part is characterized by the above-mentioned. Motor drive device. The motor drive according to any one of claims 1 to 6, wherein the signal output switching unit switches an output signal in which the switching element operates in a freewheeling diode mode according to a signal from the signal output unit. apparatus. 8. The motor drive device according to claim 1, wherein the bidirectional switching element included in the converter unit is made of GaN having at least one of a normally-off type and a double gate type. An air conditioner comprising the motor drive device according to any one of claims 1 to 8.

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