JP2010148199A - Motor drive device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a motor drive device controlling the bouncing of a DC intermediate voltage, even when the drive device has an extremely small capacitor capacitance. <P>SOLUTION: A motor voltage phase correction unit 31 is provided in a control unit 300 for performing the drive control of a three-phase inverter. The motor voltage phase correction unit 31 corrects a motor voltage phase command value so that a motor voltage current phase difference comes within a range of -90° to +90°, based on: a motor voltage current phase difference, the phase difference between the motor voltage and the motor current, generated by a phase difference operator 27; and on a target phase difference deviation, the deviation with regard to a preset target phase difference, outputted from a target phase difference setting device 28. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a motor drive device applicable to, for example, a home air conditioner.

  In general, in a motor drive device using a single-phase AC power source, the single-phase AC power source is converted to DC by a diode rectifier, and a smoothing capacitor (hereinafter simply referred to as a “capacitor”) is connected to the output to accumulate energy, and ripple is generated. The DC power source that has been removed and smoothed is converted into AC power source by an inverter to drive the motor. However, since the input current increases as the load (motor) capacity increases, it is necessary to increase the capacitor capacity. Therefore, in a motor drive device used for a normal home air conditioner, a large-capacity electrolytic capacitor of several hundred μF is used.

  On the other hand, when the capacitor capacity is increased, the DC voltage is increased and the flow angle of the diode rectifier is decreased. Therefore, the power factor is decreased and the harmonics of the input current are increased, which may cause a system failure due to the harmonic current. This countermeasure is taken by connecting a reactor to the input to suppress harmonics or using a PFC (Power Factor Control) using a semiconductor switching element.

  However, these countermeasures increase the cost of the apparatus and the external dimensions. Moreover, since the electrolytic capacitor is a life-span component, it is a factor that reduces the reliability of the apparatus.

  From the above problem, a technique for driving a motor using a small-capacitance capacitor has been disclosed (for example, Patent Documents 1 and 2).

  First, Patent Document 1 discloses a technique for controlling a torque current so that an input current becomes a sine wave in an inverter control device using a small-capacitance capacitor. Specifically, the field weakening control of the motor is performed, the harmonic current of the power supply current is controlled by controlling the torque current, and the direct current voltage is reduced by suppressing the current flowing from the power supply to the capacitor through the single-phase rectifier circuit. An attempt is made to improve the input current waveform by increasing the conduction width of the rectifier by allowing a current to flow even in a low place.

  In Patent Document 2, in an inverter control apparatus using a small-capacitance capacitor and a small-capacity reactor, a waveform improvement voltage that compensates for a distortion voltage caused by switching of the inverter is calculated based on the phase of the motor command voltage. A technique for improving an input power factor by applying a motor to a motor and suppressing a harmonic component of an AC power supply voltage is disclosed.

JP 2002-354826 A JP 2007-129866 A

  However, the technique disclosed in Patent Document 1 requires a complicated calculation for performing field-weakening control, which complicates the configuration of the control system and increases the amount of calculation. In addition, the technique disclosed in Patent Document 2 has a problem in that it is necessary to provide a small-capacity reactor in order to suppress the harmonic component of the AC power supply voltage, which affects the downsizing of the apparatus.

  Furthermore, in the techniques disclosed in Patent Document 1 and Patent Document 2, when a regenerative current is generated from the motor, the regenerative current flows into the DC intermediate circuit and the DC intermediate voltage jumps (hereinafter, “DC intermediate voltage jumps”). Occurs). Therefore, there is a problem that the capacitor capacity cannot be reduced unless the jump of the DC intermediate voltage is suppressed.

  The present invention has been made in view of the above, and suppresses the jump of the DC intermediate voltage while avoiding complication and enlargement of the device even when the capacitor capacity is extremely small. An object of the present invention is to provide a motor drive device capable of achieving the above.

  In order to solve the above-described problems and achieve the object, a motor drive device according to the present invention is connected to a single-phase AC power source and converts a direct current converted by the rectifier into a three-phase structure. Based on a three-phase inverter that converts to alternating current and supplies power to the motor, a capacitor connected in parallel between the rectifier and the three-phase inverter, and a motor voltage phase command value determined based on the rotational speed command value A control unit that performs drive control of the three-phase inverter, and the control unit is a deviation between a motor voltage current phase difference that is a phase difference between the motor voltage and the motor current and a preset target phase difference. A motor voltage phase correction unit that corrects the motor voltage phase command value so that the motor voltage current phase difference falls within a range of −90 ° to + 90 ° based on a certain target phase difference deviation is provided. It is characterized by.

  In the motor drive device according to the present invention, the motor voltage phase correction unit includes a phase adjuster that calculates a phase correction value obtained by multiplying the target phase difference deviation by a predetermined gain. The motor voltage phase command value is corrected using the phase correction value output from the regulator.

  In the motor drive device according to the present invention, in the above invention, the motor voltage / current phase difference is calculated based on the corrected motor voltage phase command value corrected using the phase correction value and the detected motor current. It is calculated as a phase difference from the motor current phase calculated based on the above.

  The motor driving device according to the present invention is characterized in that, in the above invention, a voltage limiting element having a function of limiting the magnitude of the applied voltage is connected in parallel with the capacitor.

  A motor driving device according to the present invention is connected to a phase AC power source, and converts a direct current into a direct current converted into direct current, converts the direct current converted by the rectifier into a three-phase alternating current, and supplies power to the motor. A voltage limiting element connected in parallel between the rectifier and the three-phase inverter, and a motor voltage phase command value determined based on the rotational speed command value. Based on the motor voltage current phase difference, which is a phase difference between the motor voltage and the motor current, and a preset target phase difference. A motor voltage phase correction unit that corrects the motor voltage phase command value so that the motor voltage current phase difference is within a range of −90 ° to + 90 ° based on a target phase difference deviation that is a deviation is provided. It is characterized by.

  In the motor drive device according to the present invention, the motor voltage phase correction unit includes a phase adjuster that calculates a phase correction value obtained by multiplying the target phase difference deviation by a predetermined gain. The motor voltage phase command value is corrected using the phase correction value output from the regulator.

  In the motor drive device according to the present invention, in the above invention, the motor voltage / current phase difference is calculated based on the corrected motor voltage phase command value corrected using the phase correction value and the detected motor current. It is calculated as a phase difference from the motor current phase calculated based on the above.

  In the motor drive device according to the present invention as set forth in the invention described above, the target phase difference is set to a value that maximizes the efficiency of the motor.

  In the motor drive device according to the present invention, in the above invention, the control unit calculates an effective current in the motor current based on the motor voltage current phase difference and the amplitude value of the motor current. And a rotation speed command value correction unit that corrects the rotation speed command value that determines the rotation speed of the motor by using the effective current output from the active current calculator as an effective current correction value. Features.

  Further, in the motor drive device according to the present invention as set forth in the invention described above, the rotation speed command value correction unit generates a DC component of the effective current from the effective current and a frequency component more than twice the single-phase AC power supply frequency. A bandpass filter for removal is provided.

  According to the present invention, the motor voltage phase correction unit is based on a target phase difference deviation that is a deviation between a motor voltage current phase difference that is a phase difference between the motor voltage and the motor current and a preset target phase difference. Since the motor voltage phase command value determined based on the rotation speed command value is corrected so that the motor voltage current phase difference is within the range of −90 ° to + 90 °, the generation of regenerative current can be suppressed. It is possible to suppress the jump of the DC intermediate voltage accompanying the generation of the regenerative current.

  Embodiments of a motor drive device according to the present invention will be described below in detail with reference to the drawings. In addition, this invention is not limited by embodiment shown below.

<Embodiment 1>
FIG. 1 is a diagram illustrating a configuration example of a motor drive device 100 according to the first embodiment. As shown in FIG. 1, the motor drive device 100 according to the first embodiment is configured to be supplied with single-phase AC power from a single-phase AC power supply 1 and drive a three-phase motor 9.

(Configuration of motor drive device)
First, the configuration of the motor drive device 100 will be described. In FIG. 1, the motor drive device 100 includes a main circuit unit 200 as a component of the drive system. The main circuit unit 200 includes, as main components, a single-phase rectifier 2 that receives AC power of a single-phase AC power source 1 that is a supply source of single-phase AC power, and a DC output of the single-phase rectifier 2 that is input. Phase inverter 6 and DC intermediate circuit 3 provided between single-phase rectifier 2 and three-phase inverter 6 are provided. The DC intermediate circuit 3 includes a very small capacitor 4 and a Zener diode 5 connected in parallel to the capacitor 4, and is connected in parallel between the single-phase rectifier 2 and the three-phase inverter 6. Connected to the three-phase inverter 6 is a three-phase motor 9 driven by the AC output of the three-phase inverter 6. In addition, as the three-phase motor 9, an induction motor, a synchronous motor, etc. are suitable.

  In addition, the motor drive device 100 has, as a component of the control system, detection values of current detectors (for example, CT) 7a, 7b, 7c and current detectors 7a, 7b, 7c that detect an input current of the three-phase motor 9. A control unit 300 that outputs a PWM signal that is input and drives the three-phase inverter 6, and a drive circuit 8 that converts the drive signal of the three-phase inverter 6 based on the PWM signal input from the control unit 300. Yes.

(Schematic function of the motor driving device 100)
Next, general functions of each part constituting the motor drive device 100 will be described. The single-phase rectifier 2 converts the alternating current supplied from the single-phase alternating current power source 1 into direct current and supplies it to the three-phase inverter 6. The three-phase inverter 6 includes, for example, three sets of switching arms including upper arm side switching elements U, V, and W and lower arm side switching elements X, Y, and Z. The direct current supplied from the single phase rectifier 2 is supplied as U It is converted into a three-phase AC of phase, V phase, and W phase and supplied to the three-phase motor 9. The DC intermediate circuit 3 smoothes the DC intermediate voltage applied from the single-phase rectifier 2. The current detectors 7a, 7b, and 7c detect the input current to the three-phase motor 9, and output it as a U-phase current, a V-phase current, and a W-phase current.

(Concept of control in motor drive device 100)
Next, the concept of control in the motor drive device 100 according to the first embodiment will be described. The phase difference between the phase voltage of the three-phase motor 9 and the phase current of the three-phase motor 9 (hereinafter referred to as “motor voltage / current phase difference”) is −90 ° or less or + 90 ° or more, that is, the motor power factor is a negative value. In this case, a regenerative current is generated from the three-phase motor 9, and the regenerative current flows into the DC intermediate circuit 3. Here, when the capacity of the capacitor 4 is extremely small, the regenerative current flowing into the DC intermediate circuit 3 cannot be sufficiently absorbed. For this reason, when the regenerative current flows into the DC intermediate circuit 3, the DC intermediate voltage jumps as described above. On the other hand, if the motor voltage / current phase difference is controlled to be within the range of −90 ° to + 90 °, that is, the motor power factor is always set to a positive value, no regenerative current is generated. Therefore, if the motor voltage / current phase difference is controlled to be within the range of −90 ° to + 90 °, it is possible to suppress the jump of the DC voltage caused by the regenerative current.

  In addition to the above control, if the motor voltage / current phase difference is controlled to be constant, the input current to the motor driving apparatus 100 has the same waveform as the input voltage. That is, if the input voltage is a sine wave, the input current can be a sine wave, and the flow angle of the input current can be widened. Therefore, the input power factor can be improved by performing constant control of the motor voltage / current phase difference.

  As described above, the motor driving apparatus 100 according to the first embodiment has the amplitude and phase of the phase voltage of the three-phase motor 9 so that the motor voltage / current phase difference is constant within the range of −90 ° to + 90 °. While performing control, the power factor control which improves the input power factor of the motor drive device 100 is performed.

  When power factor control is performed on the motor drive device, the stability of the control system may be reduced due to the influence of a DC component included in the motor current and a frequency component twice the single-phase AC frequency. Therefore, in the motor drive device 100 according to the first embodiment, control for increasing the stability of the control system is also performed. Details of this control will be described later.

(Configuration and function of control unit 300)
Next, the configuration and functions of the control unit according to the first embodiment will be described with reference to FIG. FIG. 2 is a diagram illustrating a detailed configuration example of the control unit 300 illustrated in FIG. 1.

  In FIG. 2, the control unit 300 includes a rotation speed command value correction unit 30, a motor voltage phase correction unit 31, and a motor voltage amplitude correction unit 32 as main components, and generates an input signal for these components. The three-phase / two-phase converter 11, the phase calculator 12, the amplitude calculator 13, the rotation speed setting device 14, the integrator 16, the sine wave generator 18, the phase difference calculator 27, and the target phase difference setting device 28. , And a subtractor 29, and further includes a comparator 20, a NOT calculator 21, and a carrier generator 22 as components for generating a PWM signal to the three-phase inverter 6.

  The three-phase / two-phase converter 11 converts the U-phase current, V-phase current, and W-phase current detected by the current detectors 7a, 7b, 7c (see FIG. 1) into two-axis components of the stationary coordinate system. To do. The phase calculator 12 calculates the phase (hereinafter referred to as “motor current phase”) of the phase current (hereinafter referred to as “motor current”) flowing through the three-phase motor 9 from the output of the three-phase / two-phase converter 11. The amplitude calculator 13 calculates the amplitude of the phase current flowing through the three-phase motor 9 from the output of the three-phase / two-phase converter 11 (hereinafter referred to as “motor current amplitude”).

  The phase difference calculator 27 is a motor current phase output from the phase calculator 12 and a phase voltage (hereinafter referred to as “motor voltage”) applied to a three-phase motor 9 output from a motor voltage phase correction unit 31 described later. Is calculated as a phase difference between the two phases (hereinafter referred to as “motor voltage phase”) and output as a motor voltage / current phase difference.

  The target phase setter 28 is preset with a target phase difference, which is a predetermined set value for the phase difference between the motor voltage and the motor current. Here, the target phase difference is set to a different value for each motor model. For example, when performing control that maximizes the motor efficiency, the target phase difference is set to a value in a range of approximately −45 ° to −20 °. The For such control that maximizes the efficiency of the motor, for example, a method described in Japanese Patent Application Laid-Open No. 2008-199706 may be used. The driving state of the synchronous motor is almost uniquely determined by the motor voltage current phase difference (described as power factor in Japanese Patent Application Laid-Open No. 2008-199706) and torque, so that the optimum motor voltage current level with high power consumption efficiency according to the torque is obtained. By setting the relationship with the phase difference as a table and setting the target phase difference, the motor can be operated with high efficiency.

  FIG. 3 is a diagram showing an optimum motor voltage / current phase difference characteristic with high power consumption efficiency when the torque of an IPM (Interior Permanent Magnet) motor is used as a parameter. The upper part of FIG. 3 shows changes in motor voltage / current phase difference with respect to changes in current Id using torque as a parameter, and the lower part of FIG. 3 shows changes in magnitude of motor current I with respect to changes in current Id using torque as a parameter. Is shown. Here, the current Id is a d-axis current component when a three-phase motor current is converted into a two-phase rotational coordinate system (dq coordinate system). From the upper part of FIG. 3, it can be seen that the range of possible motor voltage / current phase difference Φpf is limited by the magnitude of the torque.

  Further, since the magnitude of the current in the lower part of FIG. 3 corresponds to the resistance loss, the resistance loss is minimized when the current magnitude is the smallest, and the power consumption efficiency is maximized. When the plurality of points P1 at which the power consumption efficiency is maximized are plotted as points P2 on the corresponding torque line in the upper part of FIG. 3, the maximum efficiency line L is obtained. That is, the relationship of the motor voltage / current phase difference that maximizes the power consumption efficiency with respect to the torque is obtained.

  Accordingly, the target phase difference setting unit 28 is provided with a table in which the relationship of the motor voltage / current phase difference that maximizes the power consumption efficiency with respect to the torque described above is provided, and the motor that maximizes the power consumption efficiency with respect to the input torque. The voltage / current phase difference is output from the target phase difference setting unit 28. The input torque includes the U-phase, V-phase, and W-phase currents detected by the current detectors 7a to 7c and the motor voltage command value or the U-phase, V-phase, and W-phase detected by a motor voltage detector (not shown). Torque calculation may be performed using the above voltage.

  In the above-described control for maximizing the motor efficiency, the target value of the motor voltage / current phase difference that maximizes the power consumption efficiency with respect to the torque is set. However, the torque is the angular frequency of the synchronous motor. Since it is inversely proportional to ω, this angular frequency ω may be detected, and a target value of the motor voltage / current phase difference that maximizes the power consumption efficiency may be set with respect to the torque in consideration of the detected angular frequency. .

  In the motor drive device of the present embodiment, since the gist is to control the motor voltage / current phase difference to always be within the range of −90 ° to + 90 °, the target phase difference is equal to the motor voltage / current phase difference. It is desirable that the value be as far as possible from the upper limit of + 90 ° and the lower limit of −90 °. Therefore, as a target phase difference for performing maximum efficiency control, for example, when a value within a range of −45 ° to −20 ° can be set, it is farthest from −90 ° and + 90 °, that is, most It is preferable to select −20 ° having a phase margin as the target phase difference. By this selection, it is possible to achieve both further improvement in control accuracy when driving the motor and higher efficiency in operation.

  The subtractor 29 subtracts the motor voltage / current phase difference from the target phase difference and outputs the result as a target phase difference deviation. A rotational speed command value that determines the rotational speed of the three-phase motor 9 is preset in the rotational speed setter 14. The rotational speed command value is a set value corresponding to the mechanical angle (mechanical phase).

  The rotation speed command value correction unit 30 includes a subtracter 15, a band pass filter 25, and an active current calculator 26. The rotation speed command value correction unit 30 is a control unit that corrects the rotation speed command value based on the motor current amplitude and the motor voltage current phase difference, and is twice the DC component and single-phase AC frequency included in the motor current. It also functions as a stabilization control unit that performs control to stabilize the control system by suppressing the influence of the frequency components.

  In the rotation speed command value correction unit 30, the active current calculator 26 calculates an effective current from the motor current amplitude and the motor voltage current phase difference. The effective current is calculated by the active current calculator 26 and the motor current amplitude value obtained by calculating the amplitude calculator 13 from the output of the 3-phase / 2-phase converter 11 and the motor voltage current level output from the phase difference calculator 27. It is obtained by performing an operation of multiplying the cosine (COS) of the phase difference. When motor control becomes unstable due to sudden fluctuations in load, vibration of torque and motor current occurs. This torque or motor current vibration appears as a vibration component of the effective current, which is a direct current amount in the steady state. By feeding back the vibration component to the rotational speed command value, the vibration of the torque and motor current is suppressed and the control system is stabilized. Can be realized. In this embodiment, the band-pass filter 25 generates an effective current correction value obtained by removing the DC component included in the effective current and the frequency component more than twice the power supply frequency from the effective current, and the subtractor 15 makes the effective current value from the rotation speed command value. A reference rotational speed command value obtained by subtracting the current correction value is generated and output to the integrator 16.

  In the configuration of the rotation speed command value correction unit 30, the band pass filter 25 may be omitted, and the output of the active current calculator 26 may be input to the subtracter 15. Further, a high pass filter may be used instead of the band pass filter 25. However, in addition to the active current component, the output of the active current calculator 26 also includes a DC component and a frequency component that is twice the power supply frequency, and these components are removed by the bandpass filter 25. Therefore, stabilization control can be performed more effectively.

  The integrator 16 generates a motor voltage phase command value obtained by integrating the reference rotation speed command value. This motor voltage phase command value is a phase command value determined based on the rotation speed command value. Since the reference rotational speed command value input to the integrator 16 is a command value based on the mechanical angle (mechanical phase), the integrator 16 performs a process of multiplying the number of poles of the three-phase motor 9 by electric power. The command value is changed based on the angle (electrical phase).

  The motor voltage phase correction unit 31 is a control unit that performs control for instantaneously correcting the motor voltage phase (hereinafter referred to as “instantaneous phase correction control”), and includes an adder 17 and an instantaneous phase adjuster 24. The instantaneous phase adjuster 24 is, for example, a proportional controller (P control), and calculates an instantaneous phase correction value obtained by multiplying a target phase difference deviation by a predetermined gain. The gain of the instantaneous phase adjuster 24 is preferably set to 1 or less so that the control system does not diverge. The adder 17 adds the instantaneous phase correction value to the motor voltage phase command value, and outputs the added value as the motor voltage phase.

  Note that the meaning of “instantaneous” here means that the control input is reflected in the control system without delaying rather than being controlled with a certain delay time like an integrator, for example. is there.

  The sine wave generator 18 generates sine wave command values before amplitude modulation in the U phase, V phase, and W phase from the motor voltage phase, and U phase sine wave command value, V phase sine wave command value, and W phase sine wave. The command value is output to the motor voltage amplitude correction unit 32.

  The motor voltage amplitude correction unit 32 is a control unit that generates a voltage command value obtained by correcting each phase sine wave command value based on the target phase difference deviation, and includes a multiplier 19 and a voltage amplitude adjuster 23. The voltage amplitude adjuster 23 is, for example, an integral controller (I control) or a proportional integral controller (PI control), and generates a voltage amplitude command value to be multiplied by the sine wave command value based on the target phase difference deviation. The multiplier 19 generates a U-phase voltage command value, a V-phase voltage command value, and a W-phase voltage command value obtained by multiplying the voltage amplitude command value and each phase sine wave command value, and outputs them to the comparator 20.

  The carrier generator 22 generates a PWM carrier necessary for generating a drive signal for driving the three-phase inverter 6. The comparator 20 compares the U-phase, V-phase, and W-phase voltage command values with the PWM carrier, and each U-phase PWM signal is a PWM signal of the upper arm side switching elements U, V, and W of the three-phase inverter 6. The V-phase PWM signal and the W-phase PWM signal are output. The NOT calculator 21 performs a NOT calculation of the U-phase PWM signal, the V-phase PWM signal, and the W-phase PWM signal, and an X-phase PWM signal that is a PWM signal of the lower arm side switching elements X, Y, and Z of the three-phase inverter 6. , Y phase PWM signal and Z phase PWM signal are output.

(Effects of the motor driving device of the present embodiment)
Next, the effect of the motor drive device 100 according to the first embodiment will be described in relation to the control operation of each component described above.

First, the operation principle of the motor driving apparatus according to the first embodiment will be described again.
This operating principle is
(1) The regenerative current does not flow if the voltage can be controlled between the phase difference between the voltage and the current being always −90 ° to + 90 °.
(2) If the voltage-current phase difference is constant, the current has the same waveform as the input voltage. That is, if the input voltage is a sine wave, the input current can be a sine wave.
It was that.

In this embodiment, a motor voltage phase correction unit 31 that performs instantaneous phase correction control is provided as a control unit that controls the motor voltage current phase difference to be −90 ° to + 90 ° (see FIG. 2). ). Here, without providing the motor voltage phase correction unit 31 that performs instantaneous phase correction control, a control unit that controls the voltage amplitude so that the phase difference becomes the target phase difference (a normal power factor control system, an example of FIG. 2). Then, it is considered that only “corresponding to“ motor voltage amplitude correction unit 32 ”) may be used. Therefore, FIG. 4 shows the result of the simulation performed under these conditions. The main parameters in the simulation of FIG. 4 are as follows.
・ Single phase AC voltage: AC200V
・ Single-phase AC frequency: 50Hz
・ Reactance of input system: 100μH
・ PWM carrier frequency: 40 kHz
・ Capacitance of DC intermediate circuit: 2μF

  As shown in FIG. 4, the motor voltage / current phase difference fluctuates rapidly during a half cycle of single-phase alternating current (see FIG. 4 (a)), and when the motor voltage / current phase difference becomes −90 ° or less. A regenerative current is generated, and the DC intermediate voltage jumps (see FIG. 4C). In addition, the input current does not flow in the second half of the half cycle of the single-phase alternating current (see FIG. 4D), and the input power factor is deteriorated.

  That is, when the instantaneous phase correction control is not performed, it can be seen that the voltage / current phase difference fluctuates rapidly according to the cycle of the input current. This is because when the DC voltage fluctuates due to ripple voltage generated due to the extremely small capacity of the DC intermediate capacitor, the responsiveness of the voltage control is slow, so the motor voltage current phase difference is dominated by the current of the motor current. This means that the voltage / current phase difference cannot be controlled. At this time, since the motor voltage current phase difference exceeds −90 °, a regenerative current flows and a DC voltage jumps. Also, the input current does not flow in the latter half of the half cycle of the waveform, and the power factor is deteriorated.

  On the other hand, FIG. 5 shows a simulation result when instantaneous phase correction control by the instantaneous phase adjuster 24 is performed. Here, the simulation conditions are the same as in FIG.

  As shown in FIG. 5, the motor voltage / current phase difference gradually varies within a range of −90 ° to + 90 ° during a half-cycle period of single-phase alternating current (see FIG. 5A). No regenerative current is generated, and no jump of DC intermediate voltage occurs (see FIG. 5C). Further, the flow angle of the input current is widened (see FIG. 5D), and the input power factor is improved as compared with FIG.

  Here, when instantaneous phase correction control is performed, the motor voltage / current phase difference is not constant (see FIG. 5A), but control is performed so that the motor voltage / current phase difference approaches the target phase difference. Therefore, as compared with FIG. 4, the fluctuation of the motor voltage current phase difference is gentle, and there is no movement in which the motor voltage current phase difference exceeds −90 °. Therefore, no regenerative current flows and no DC voltage jumps. Also, the input current waveform has a wider distribution angle, and the input power factor is improved.

  By the way, when the direct current intermediate voltage is close to 0, there is a concern that the control of the motor voltage / current phase difference cannot be controlled due to insufficient voltage. This phenomenon is because the input voltage is smaller than the induced voltage when the input voltage is near zero. In this case, since the current cannot be controlled due to nonlinearity due to the diode, the motor voltage / current phase difference cannot be sufficiently controlled. For this reason, when the input voltage is around 0, the DC voltage may jump up.

  On the other hand, in motor drive device 100 of the present embodiment, zener diode 5 that is a DC voltage limiting element is connected to capacitor 4 in parallel, so that jumping of DC intermediate voltage can be suppressed. For this reason, each switching element provided in the inverter 6 can be protected from overvoltage.

  Note that the jump of the DC intermediate voltage when the input voltage is near 0 has a large voltage difference up to the allowable voltage, and a certain amount of jump can be absorbed by the capacitor 4. Therefore, it is not necessary to increase the capacity of the DC voltage limiting element.

  Further, as a factor of the jump of the DC intermediate voltage, there is regeneration of the motor reactance energy to the DC circuit side when the motor is stopped. Therefore, it is necessary to select a DC voltage limiting element having a capacity capable of absorbing energy exceeding the allowable voltage. However, since the energy stored in the reactance is not so large, it is not necessary to increase the capacity of the DC voltage limiting element. That is, the DC overvoltage can be protected by the small-capacity DC voltage limiting element.

  The capacitor 4 has a function for filtering a voltage that varies depending on the carrier and for absorbing a sudden change in current until the voltage across the Zener diode 5 (zener voltage) is limited. Therefore, the capacitance of the capacitor 3 depends on the filter effect of the carrier frequency, the energy absorption capability of the motor reactor, the allowable value for the jump of the DC voltage associated with the absorption of the motor current in the vicinity of the voltage 0, and the like. With a carrier of 20 kHz and a motor capacity of 2 kW, even with about 2 μF functions sufficiently due to parallel connection with a Zener diode.

  As described above, according to the motor driving apparatus of the first embodiment, the motor voltage phase command value is corrected so that the motor voltage / current phase difference falls within the range of −90 ° to + 90 °. Even when the capacitor of the DC intermediate circuit has a very small capacity (for example, 2 μF or less), the generation of the regenerative current can be suppressed, and the jump of the DC intermediate voltage accompanying the generation of the regenerative current can be suppressed. .

  Further, according to the motor drive device of the first embodiment, the input current waveform of the motor drive device is improved by controlling the motor voltage / current phase difference to be constant within the range of −90 ° to + 90 °. The input power factor can be improved.

  Further, according to the motor driving apparatus of the first embodiment, the target phase difference is set so that the motor efficiency is maximized, thereby efficiently converting the electric power supplied from the AC power source into the driving force of the motor. Is possible.

  Further, according to the motor driving apparatus of the first embodiment, the control system is calculated by calculating the effective current correction value obtained by removing the DC component of the effective current and the frequency component more than twice the power supply frequency from the effective current of the motor. It becomes possible to improve the stability.

  Further, according to the motor drive device of the first embodiment, since it is not necessary to perform complicated control such as field weakening control, the device can be prevented from becoming complicated and large, and a simple control system can be configured. Become.

<Embodiment 2>
FIG. 6 is a diagram illustrating a configuration example of the motor drive device 100a according to the second embodiment. As shown in FIG. 6, the main circuit unit 200a, which is a component of the drive system of the motor drive device 100a according to the second embodiment, includes only the Zener diode 5 in the DC intermediate circuit 3a and omits the capacitor 4. Yes. The control unit 300 is the same as FIG. 2 described in the first embodiment. Note that the same or similar components as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

  In the motor drive device of the first embodiment, since the method of correcting the motor voltage phase command value is adopted so that the motor voltage current phase difference is within the range of −90 ° to + 90 °, the generation of regenerative current is suppressed. The capacitor of the DC intermediate circuit can be made extremely small (for example, 2 μF or less).

  On the other hand, many voltage limiting elements such as Zener diodes and varistors have a certain capacitance value. Therefore, it is possible to substitute a voltage limiting element such as a Zener diode or a varistor as a capacitor. That is, the motor driving apparatus of the second embodiment shown in FIG. 6 makes the Zener diode 5 function as a capacitive element and a voltage limiting element.

  The configuration of the control system is the same as that of the motor drive device of the first embodiment, and therefore the same effect as that of the first embodiment can be obtained.

  Further, according to the motor drive device of the second embodiment, since the capacitor can be omitted, an ultimate capacitor-less motor drive device can be realized.

  Note that the configuration shown in the above embodiment is an example of the configuration of the present invention, and can be combined with another known technique, and a part of the configuration is omitted without departing from the gist of the present invention. Of course, it is possible to change and configure.

  In the embodiment, the drive control of the motor drive device to which the present invention is applied is described as being implemented by power factor control. However, the drive control method is not limited to this, and vector control or other Of course, it is possible to apply to the control method.

  Furthermore, in the embodiment, the contents of the invention have been described for a motor drive device that is assumed to be applied to a home air conditioner as a motor drive device to which the present invention is applied, but the application field is not limited to this. Of course, application to various industrial application fields is possible.

  As described above, the motor drive device according to the present invention is useful as an invention capable of suppressing the jump of the DC intermediate voltage even when the capacitor capacity is extremely small.

1 is a diagram illustrating a configuration example of a motor drive device according to a first exemplary embodiment; It is a figure which shows the detailed structural example of the control part 300 shown in FIG. It is a figure which shows the optimal motor voltage electric current phase difference characteristic with high power consumption efficiency when the torque of an IPM motor is used as a parameter. It is a figure which shows the simulation result at the time of providing only the control part which controls a voltage amplitude so that a phase difference may turn into a target phase difference, without providing the motor voltage phase correction part which performs instantaneous phase correction control. It is a figure which shows the simulation result at the time of performing the instantaneous phase correction control by an instantaneous phase adjuster. FIG. 6 is a diagram illustrating a configuration example of a motor drive device according to a second exemplary embodiment;

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Single-phase alternating current power supply 2 Single-phase rectifier 3, 3a DC intermediate circuit 4 Capacitor 5 Zener diode 6 Three-phase inverter 7a, 7b, 7c Current detector 8 Drive circuit 9 Three-phase motor 11 Three-phase / two-phase converter 12 Phase calculation 13 Amplitude calculator 14 Rotation speed setter 15 Subtractor 16 Integrator 17 Adder 18 Sine wave generator 19 Multiplier 20 Comparator 21 NOT calculator 22 Carrier generator 23 Voltage amplitude adjuster 24 Instantaneous phase adjuster 25 Band Pass filter 26 Effective current calculator 27 Phase difference calculator 28 Target phase difference setter 29 Subtractor 30 Speed command value correction unit 31 Motor voltage phase correction unit 32 Motor voltage amplitude correction unit 100, 100a Motor drive device 200, 200a Main Circuit unit 300 Control unit

Claims (10)

A rectifier connected to a single-phase AC power source and converting AC to DC;
A three-phase inverter that converts the direct current converted by the rectifier into a three-phase alternating current and supplies electric power to the motor;
A capacitor connected in parallel between the rectifier and the three-phase inverter;
A control unit that performs drive control of the three-phase inverter based on a motor voltage phase command value determined based on a rotation speed command value;
With
The control unit determines the motor voltage / current phase difference based on a target phase difference deviation that is a deviation between a motor voltage / current phase difference that is a phase difference between the motor voltage and the motor current and a preset target phase difference. A motor drive device comprising a motor voltage phase correction unit that corrects the motor voltage phase command value so as to be within a range of -90 ° to + 90 °.   The motor voltage phase correction unit includes a phase adjuster that calculates a phase correction value obtained by multiplying the target phase difference deviation by a predetermined gain, and uses the phase correction value output from the phase adjuster to output the motor voltage phase command. The motor driving apparatus according to claim 1, wherein the value is corrected.   The motor voltage / current phase difference is calculated as a phase difference between a corrected motor voltage phase command value corrected using the phase correction value and a motor current phase calculated based on the detected motor current. The motor drive device according to claim 1, wherein:   The motor drive device according to any one of claims 1 to 3, wherein a voltage limiting element having a function of limiting a magnitude of an applied voltage is connected in parallel with the capacitor. A rectifier connected to a single-phase AC power source and converting AC to DC;
A three-phase inverter that converts the direct current converted by the rectifier into a three-phase alternating current and supplies electric power to the motor;
A voltage limiting element having a function of limiting the magnitude of an applied voltage, and connected in parallel between the rectifier and the three-phase inverter;
A control unit that performs drive control of the three-phase inverter based on a motor voltage phase command value determined based on a rotation speed command value;
With
The control unit determines the motor voltage / current phase difference based on a target phase difference deviation that is a deviation between a motor voltage / current phase difference that is a phase difference between the motor voltage and the motor current and a preset target phase difference. A motor drive device comprising a motor voltage phase correction unit that corrects the motor voltage phase command value so as to be within a range of -90 ° to + 90 °.   The motor voltage phase correction unit includes a phase adjuster that calculates a phase correction value obtained by multiplying the target phase difference deviation by a predetermined gain, and uses the phase correction value output from the phase adjuster to output the motor voltage phase command. The motor driving apparatus according to claim 5, wherein the value is corrected.   The motor voltage / current phase difference is calculated as a phase difference between a corrected motor voltage phase command value corrected using the phase correction value and a motor current phase calculated based on the detected motor current. The motor drive device according to claim 5 or 6, wherein   The motor drive device according to claim 1, wherein the target phase difference is set to a value that maximizes the efficiency of the motor.   The control unit includes an active current calculator that calculates an effective current in the motor current based on the motor voltage / current phase difference and the amplitude value of the motor current, and the effective current output by the effective current calculator is effective. The rotation speed command value correction | amendment part which correct | amends the said rotation speed command value which determines the rotation speed of the said motor using as an electric current correction value was further provided, The any one of Claims 1-8 characterized by the above-mentioned. Motor drive device.   The rotation speed command value correction unit includes a band-pass filter that removes a DC component of the effective current and a frequency component more than twice the single-phase AC power supply frequency from the effective current. The motor drive device described in 1.

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