JP5718474B2 - Power conversion device, electric motor drive device, and air conditioner - Google Patents

Description

  The present invention relates to a control technique for a power converter using a PWM (Pulse Width Modulation) control method.

  There is a strong demand for miniaturization, high efficiency, and high output by reducing the number of parts in electric motor drive devices used in air conditioners and the like, and various technologies for realizing these demands have been developed. As one of the methods for driving the electric power converter used in such an electric motor drive device and the electric motor serving as a load thereof with high efficiency, 180 degree energization is performed in which the current flowing from the electric power converter to the electric motor is PWM-controlled in a sine wave form. Disclosed is a 180 degree / 120 degree energization switching technique that switches between a method and a 120 degree energization method that performs a PWM control every 120 degrees with reference to the phase of the induced voltage depending on the load conditions and drive conditions of the motor. Has been. It is described that by using this method, high-efficiency driving can be performed according to the load condition and driving condition of the motor, and the driving of the motor can be stabilized over a wide range of rotation speeds (see Patent Document 1). .

  Further, as a method of reducing the loss of the motor when the power conversion device that performs PWM control is energized at 120 degrees, the energization angle at the time of 120 degrees energization is expanded to 150 degrees energization by a torque command, so that the current flowing through the motor is sinusoidal. A 120-degree / 150-degree energization switching technique that reduces pulsation of torque close to a wave is disclosed. It is described that, by using this method, the motor can be driven with high performance at the time of starting the motor and from a heavy load to a light load with a rotational force with less noise and vibration (see Patent Document 2). .

  In addition, when operating a motor using a three-phase power converter that performs PWM control, in the case of vector control of the power converter, two-arm modulation is performed without switching only the phase where the current value is close to zero. A technique of a two-phase modulation system that performs (two-phase modulation) is also disclosed. According to this technique, in the case of performing vector control without a position sensor, the zero clamp phenomenon in which the stator current of the motor is zero clamped can be avoided by performing the two-phase modulation at the timing of each constant electrical angle. . As a result, it is possible to improve the stability of the control system in vector control over the entire load range (see Patent Document 3).

JP 2008-172948 A JP 2003-169491 A Japanese Patent Laid-Open No. 11-164597

  The 120-degree energization method and the 150-degree energization method described in Patent Document 1 and Patent Document 2 have a narrower switching operation region in one cycle than the 180-degree energization method, and thus reduce the switching loss of the power conversion device. It is possible. However, in order to detect the magnet position of the motor without using the magnet position sensor (that is, position detection), an induced voltage detection circuit is provided to acquire phase information of the induced voltage during the stop period of the switching operation. It is necessary to switch the phase for performing the switching operation based on the phase information.

  In other words, the 120-degree energization system and the 150-degree energization system of the magnet position sensorless system must always provide a period for stopping the switching operation near the zero cross of the induced voltage of the motor. Therefore, it is difficult to extend the switching operation period to an electrical angle of 150 degrees or more. Further, the switching operation stop period must be performed in synchronization with the induced voltage phase. However, there is a difference between the induced voltage phase and the current phase of the electric motor depending on the load condition and driving condition. Therefore, even if the 150-degree energization method is used, the effect of reducing torque pulsation is not always obtained. Further, if it is attempted to prevent a deviation between the phase of the induced voltage and the current phase of the electric motor, the operation of energization at 150 degrees may be impossible.

  That is, the 120-degree energization method and the 150-degree energization method determine the energization section and the open phase section (section in which both the upper and lower arm switching elements of the inverter are stopped) based on the phase of the induced voltage. In order to acquire a position signal in the magnet position sensorless system, it is necessary to include the zero cross point of the induced voltage in the open phase section. However, since a phase difference between the induced voltage and the motor current phase occurs depending on the load condition and driving condition, the zero cross point of the induced voltage may not be included in the open phase section. As a result, position detection may not be performed accurately when vector control is performed based on the phase of the induced voltage without a magnet position sensor. In other words, although the switching loss can be reduced by stopping the switching operation in a predetermined section, vector control based on accurate position detection cannot be performed.

  As described above, in the methods of Patent Document 1 and Patent Document 2, it is possible to reduce the number of times of switching of the power conversion circuit by providing a section in which switching is stopped during driving of the 120-degree energization method and the 150-degree energization method. . However, the phase information of the induced voltage is obtained using an induced voltage detection circuit and the like, and the phase to be switched is switched based on the phase information of the induced voltage. Position detection cannot be performed. As a result, current distortion may increase and torque pulsation of the motor may increase. In addition, in the 180-degree energization drive according to Patent Document 1, the current flowing through the motor can be controlled in a sine wave without using an induced voltage detection circuit or the like, but the switching operation is always performed during one cycle of voltage and current. Therefore, switching loss increases and the efficiency of the power conversion circuit decreases.

  In the technique disclosed in Patent Document 3, when performing vector control using a three-phase power converter that performs PWM control, only the phase whose current value is close to zero is paused to perform two-phase modulation. Is going. However, since there is no current rest period, the copper loss of the motor occurs. That is, even if the two-phase modulation method described in Patent Document 3 is used, the switching loss of PWM control cannot be reduced and the efficiency of the power converter cannot be improved.

  This invention is made | formed in view of such a situation, and makes it a subject to reduce the switching loss at the time of PWM control, and to provide a highly efficient power converter device.

In order to solve the above problems, a power conversion device according to the present invention is a power conversion device that performs power conversion for driving an electric motor by PWM control using a vector control method, and performs the PWM control. A power control circuit configured to include a pulse control unit that outputs a pulse signal, and a switching element having a three-phase configuration, and that converts DC power into AC power using the pulse signal output from the pulse control unit; and A current detection unit that detects a current of a power conversion circuit; a vector control unit that performs vector control based on the current detected by the current detection unit and generates a command voltage to the pulse control unit; and the power conversion circuit to stop the positive and negative sides of the switching elements of a given phase, it determined the said pulse signal of a defined section a current phase of the power conversion circuit based Over the interval generates Rupa pulse stop control signal is stopped, includes a pulse stop control section for outputting a pulse stop control signal to the pulse control unit.

  ADVANTAGE OF THE INVENTION According to this invention, the switching loss at the time of PWM control can be reduced, and a highly efficient power converter device can be provided.

It is a block diagram which shows the circuit structure of the power converter device of the PWM control system which concerns on 1st Embodiment. In a comparative example, it is a wave form chart showing the relation of the alternating voltage which flows into an electric motor, an alternating current, and a pulse signal, (a) expresses a PWM carrier signal and an applied voltage command, (b) expresses a U phase alternating current, (C) represents a pulse signal. It is a wave form diagram which shows the relationship between the alternating voltage which flows into an electric motor in 1st Embodiment, an alternating current, and a pulse signal, and a phase pulse stop control signal, (a) represents a PWM carrier signal and an applied voltage command, ( b) represents a U-phase alternating current, (c) represents a pulse signal, and (d) represents an open phase control signal. It is a wave form chart showing the relation of U phase voltage, U phase current, and a pulse signal at the time of driving a real machine provided with a power converter of a 1st embodiment, (a) expresses U phase terminal voltage, (b) Represents a U-phase current, and (c) represents a pulse signal. It is a characteristic view which shows the relationship of the power conversion circuit loss with respect to a phase pulse stop area (open phase area), the motor loss, and the total loss which added them with the power converter device of 1st Embodiment. It is a block diagram which shows the circuit structure of the power converter device of the PWM control system of a comparative example. It is a wave form diagram which shows the relationship between the alternating voltage which flows into an electric motor, an alternating current, and a pulse signal, and a phase pulse stop control signal in the modification of the power converter device which concerns on 1st Embodiment, (a) is a PWM carrier signal and (B) represents a U-phase alternating current, (c) represents a pulse signal, and (d) represents an open phase control signal. It is a block diagram which shows the circuit structure of the power converter device of the PWM control system which concerns on 2nd Embodiment. It is a characteristic view which shows the example of a setting of the phase pulse stop area (open phase area) in the power converter device of 2nd Embodiment, (a) represents the case where it sets to the rotational speed N1 ideally, (b) is A case where the rotation speed N2 is changed at a constant change rate from the rotation speed N3 is represented, and (c) represents a case where the rotation speed N2 is changed from the rotation speed N2 to the rotation speed N3 by a predetermined curve. It is a whole block diagram of the air conditioner using the power converter device which concerns on 3rd Embodiment. It is a characteristic view which shows the relationship of the efficiency with respect to the rotational speed of the compressor drive motor in the air conditioner shown in FIG.

  Next, modes for carrying out the invention (hereinafter referred to as “embodiments”) will be described in detail with reference to the drawings as appropriate.

"Overview"
The power conversion device according to the present embodiment includes a power conversion circuit (inverter) that converts DC power into AC power using a PWM control pulse signal, detects a current flowing through the power conversion circuit, and vectorizes the power conversion circuit. And a vector control unit for controlling. Further, an open phase section is provided in which the pulse signal in the section determined with reference to the zero cross point of the current phase flowing through the power conversion circuit is stopped, and the switch elements of the upper and lower arms of the same phase are stopped. As a result, the number of switching operations during PWM control can be reduced to reduce switching loss, and accurate position information of the magnet position of the motor can be obtained from the zero cross point of the current phase by providing an open phase section. Can do. As a result, it is possible to perform stable vector control and improve the efficiency of the power conversion circuit (inverter) and the electric motor.

  Hereinafter, embodiments of a power conversion device according to the present invention will be described in detail with reference to the drawings. Note that components having the same function are denoted by the same reference symbols throughout the drawings for describing the embodiments, and the repetitive description thereof will be omitted. In the embodiment described below, the contents of this embodiment will be described in comparison with a comparative example using a conventional method in order to facilitate understanding.

<< First Embodiment >>
FIG. 1 shows a circuit configuration of a PWM control power converter 1a according to the first embodiment. In the power conversion device 1a of the first embodiment, as shown in FIG. 1, the AC motor 3 that is a permanent magnet synchronous motor is driven by vector control by the power conversion circuit 4 that is constituted by a three-phase inverter driven by PWM control. The control method when a phase pulse stop section (that is, an open phase section) is provided in the pulse signal of the power conversion circuit 4 will be described.

<Circuit configuration of power converter>
As shown in FIG. 1, the power conversion device 1 a includes a power conversion circuit 4 including a three-phase inverter that converts DC power into AC power, and a motor current that flows through an AC motor (motor) 3 connected to the power conversion circuit 4. And a control device 5a that performs vector control using a pulse signal that performs PWM control based on phase current information (current) 6A detected by the phase current detection unit 6. Is done. The power conversion circuit 4 includes a power conversion main circuit 41 including three-phase semiconductor switching elements Sup, Sun, Svp, Svn, Swp, and Swn in which IGBTs (Insulated Gate Bipolar Transistors) and diodes are anti-parallel. And a gate driver 42 that generates a gate signal supplied to the IGBT of the power conversion main circuit 41 based on the pulse signal 7A from the pulse control unit 7.

The control device 5a also includes a pulse control unit 7 that supplies a pulse signal 7A controlled based on an applied voltage command (command voltage) V ^* to the gate driver 42, and a phase current detected by the phase current detection unit 6. A vector control unit 8 that performs vector control using the information 6A and calculates the applied voltage command V ^* , and a phase pulse stop section near the current zero cross based on the current phase information (current phase) 8A calculated by the vector control (Open phase section) It is constituted by a pulse stop control unit 9 that outputs a phase pulse stop control signal (pulse stop control signal) 9A for stopping the pulse signal 7A of δ to the pulse control unit 7.

  Here, the vector control unit 8 is, for example, Non-Patent Document 1 (Sakamoto et al., “Simple Vector Control of a Position Sensorless Permanent Magnet Synchronous Motor for Home Appliances”, D. Vol. 124, No. 11 (2004) pp. 1133-1140) and Non-Patent Document 2 (Tohari et al., "Study of a New Vector Control Method for a High-Speed Permanent Magnet Synchronous Motor", D. Vol. 129, No. 1 (2009) pp. 36-45) As described in, the inverter output current is detected, three-phase to two-phase conversion (dq conversion; direct-quadrature conversion) is performed and fed back to the control system, and the inverter is driven again by two-phase to three-phase conversion. This can be realized by using general vector control, and the control method is not specified. Therefore, since the operation of the vector control unit 8 is a well-known technique, a detailed description thereof is omitted.

<Comparative example>
Here, in order to clarify the switching operation at the time of PWM control in the power conversion device 1a of the first embodiment, the PWM control in the power conversion device 1b (see FIG. 6) of the comparative example using the conventional method is illustrated in FIG. This will be described with reference to FIG. FIG. 2 is a waveform diagram showing the relationship between an AC voltage, an AC current, and a pulse signal flowing through the AC motor 3 in a comparative example, where the horizontal axis indicates the voltage phase, and the vertical axis indicates the levels of the voltage, current, and pulse signal. ing. FIG. 6 shows a circuit configuration of a power conversion device 1b of the PWM control method of the comparative example. In FIG. 6, elements having the same reference numerals as those in FIG. 1 have the same functions. The vector control performed by the vector control unit 8 is the same control method as in FIG.

As shown in FIG. 2A, the control device 5b shown in FIG. 6 generates a PWM pulse signal by comparing the PWM carrier signal and the applied voltage command V ^* as shown in FIG. Further, the command value of the applied voltage command V ^* is obtained by performing calculation by the vector control unit 8 based on the phase current information 6A detected by the phase current detection unit 6. Here, the acquisition of the phase current information 6A by the phase current detection unit 6 is performed by directly detecting the AC output current by CT (Current Transformer) as disclosed in FIG. 1 of JP-A-2004-48886, for example. Alternatively, as disclosed in FIG. 12 of the same publication, the current information of the DC bus may be acquired by a shunt resistor, and the phase current may be reproduced based on this current information.

Next, the relationship between the AC voltage and AC current supplied from the power converter 1b (see FIG. 6) to the AC motor 3 and the pulse signal will be described in detail with reference to FIG. FIG. 2A shows the PWM carrier signal and the applied voltage command V ^*, and the U-phase applied voltage command Vu ^* is representatively shown. Here, θv represents a voltage phase based on the U phase.

In the PWM control method, as shown in FIG. 2A, the pulse control unit 7 performs the pulse shown in FIG. 2C based on the U-phase applied voltage command Vu ^* and the triangular wave carrier signal (PWM carrier signal). To generate the signals “GPU +: U-phase upper element (Sup) pulse signal” and “GPU−: U-phase lower element (Sun) pulse signal”, and drive the power conversion main circuit 41 with this pulse signal. To the gate driver 42. In other words, the GPU + pulse signal and the GPU- pulse signal are opposite in positive and negative (1, 0).

  The power conversion main circuit 41 performs PWM control by this pulse signal (GPU + / GPU− pulse signal), whereby a U-phase AC current Iu as shown in FIG. Here, φ represents the phase difference between voltage and current.

  Further, the vector control unit 8 controls the amplitude of the voltage and the phase difference φ between the voltage and the current by performing vector control based on the phase current information 6A including the U-phase AC current Iu.

  As shown in FIG. 2, in the PWM control according to the comparative example, the switching operation is always performed during one period of the voltage / current, and the current is supplied by 180 degrees. More switching times than current energization. Therefore, with 180 degree energization, the switching loss resulting from this increases.

<Operation of Pulse Stop Control Unit in First Embodiment>
In the following description, the operation of the pulse stop control unit 9 (see FIG. 1) for temporarily stopping the switching operation of the pulse signal for performing the PWM control will be described with reference to FIGS. Therefore, the description of the basic operation of the PWM control described in the comparative example is omitted to avoid duplication.

  FIG. 3 is a waveform diagram showing the relationship between the AC voltage, AC current and pulse signal flowing through the AC motor 3 and the phase pulse stop control signal in the first embodiment, with the horizontal axis representing the voltage phase and the vertical axis representing the voltage. , Current, pulse signal, and open phase control signal (phase pulse stop control signal) levels. That is, FIG. 3 is a waveform diagram of this embodiment shown in contrast to the waveform diagram of FIG.

  As shown in FIG. 3D, the pulse stop control unit 9 uses the zero cross point φ of the current phase controlled by the vector control as a reference, and the phase φ and the phase φ + π are as shown in the following formula (1). During the phase pulse stop period (open phase period) δ, the pulse signals GPU + and GPU− both output a phase pulse stop control signal (open phase control signal) 9A for stopping switching to the pulse controller 7. The phase pulse stop control signal 9A outputs “0” when switching is stopped for both the pulse signals GPU + and GPU−, and “1” when switching in the PWM control system of the comparative example is performed without stopping switching.

  That is, as can be seen from equation (1), when φ is the phase difference between voltage and current and δ is the phase pulse stop period (open phase period), the voltage phase θv with respect to the U phase is φ−δ / When 2 <θv <φ + δ / 2 and φ + π−δ / 2 <θv <φ + π + δ / 2, switching by the pulse signals GPU + and GPU− is stopped. In other cases, switching is performed using pulse signals GPU + and GPU−.

  For this reason, both the pulse signals GPU + and GPU− are turned off in the phase pulse stop section δ of the phase pulse stop control signal 9A. Therefore, as shown in FIG. 3C, the pulse controller 7 outputs a signal train of pulse signals paused in the phase pulse stop period δ. In other words, the phase pulse stop section (open phase section) δ is set twice during one period of voltage and current. In the case of the configuration of the first embodiment, not only the sinusoidal PWM control method but also the two-phase modulation type PWM control method and the third harmonic addition type PWM control method are the target PWM control modulation methods. It is possible to provide a pulse stop interval δ.

  As described above, the pulse signals GPU + and GPU− provided with the period for stopping the switching operation by the pulse stop control unit 9 of the first embodiment are applied to the applied voltage phase and the AC motor 3 in the switching stop period and the switching operation period. The shape is not provided based on the induced voltage phase. That is, the switching stop period and the switching operation period of the pulse signals GPU + and GPU− are set with reference to the zero cross point of the current phase.

  In other words, in the comparative example, since the pulse signal is based on the voltage phase of the induced voltage, as shown in FIG. 2 (c), the pulse signal sequence has symmetrical ON / OFF duty before and after the zero cross point of the voltage. It becomes the shape to become. However, in the first embodiment, since the phase pulse stop section δ is provided based on the current phase (that is, not a pulse signal based on the voltage phase), as shown in FIG. The ON / OFF duty of the pulse signal train is not symmetrical before and after the voltage zero-cross point. That is, in the first embodiment, the ON / OFF duty of the pulse signal train is asymmetric before and after the current zero-cross point.

  Thus, in the first embodiment, since the phase pulse stop section δ is provided in the section including the zero cross point of the current, as shown in FIG. 3C, before and after the phase pulse stop section δ as the center. The pulse signal trains A and B have an asymmetric shape. From this, when the phase pulse stop section δ is provided in the section including the zero cross point of the current as in the first embodiment, it is observed whether the pulse signals before and after the phase pulse stop section δ are asymmetric. Thus, it can be easily determined whether or not the first embodiment is applied.

<Waveforms when driving with actual machine>
FIG. 4 is a waveform diagram showing the relationship between the U-phase voltage, the U-phase current, and the pulse signal when the real machine including the power conversion device 1a according to the first embodiment is driven. Fig. 4 shows voltage, current, and pulse signal levels. That is, FIG. 4 is a method in which a phase pulse stop period is provided in the vicinity including the zero cross point of the current according to the first embodiment, and the actual machine is driven by setting the phase pulse stop period in the two-phase modulation type PWM control method. Shows the voltage, current and pulse signal.

  4A shows the U-phase terminal voltage Vun of the power conversion main circuit 41, FIG. 4B shows the U-phase current Iu flowing through the AC motor 3, and FIG. 4C shows the pulse signals GPU + and GPU−. .

  As shown in FIG. 4C, the switching signals of the pulse signals GPU + and GPU− are both turned off in the section (indicated by δ) sandwiched by the alternate long and short dash line, and the phase pulse stop section δ is set. I can confirm that. Further, since the phase pulse stop section δ is set, it can be confirmed that the U-phase current Iu becomes zero in the section sandwiched by the alternate long and short dash line.

<Effects of First Embodiment>
FIG. 5 is a characteristic diagram showing a relationship between the power conversion circuit loss, the motor loss, and the total loss obtained by adding them to the phase pulse stop period (open phase period) δ by the power conversion device 1a of the first embodiment. The horizontal axis represents the phase pulse stop interval (open phase interval) δ, and the vertical axis represents the loss. That is, FIG. 5 shows the characteristics of the total pulse loss including the phase pulse stop interval δ set by the pulse stop control unit 9 and the loss of the power conversion circuit 4, the loss of the AC motor 3, and these two losses.

  As shown in FIG. 5, the loss (power conversion circuit loss) of the power conversion circuit 4 of the first embodiment is caused by the fact that the number of switching times decreases as the phase pulse stop interval δ increases. To reduce. Further, the loss of the AC motor 3 (motor loss) increases due to the increase in the harmonic component of the current by providing the phase pulse stop section δ. Furthermore, since the increase of the harmonic component of the current becomes significant due to the increase of the phase pulse stop section δ, the increase in loss (motor loss) of the AC motor 3 due to this increases. For this reason, as shown in FIG. 5, there is a phase pulse stop section δopt in which the total loss obtained by adding these two losses (power conversion circuit loss and motor loss) is minimum, and the phase pulse stop section δ is represented by this phase pulse. By setting the stop section δopt, it is possible to reduce the loss of the entire power conversion device 1a.

  As described above, by using the pulse stop control unit 9, it is possible to reduce the number of switching of the pulse signal for performing the PWM control with the configuration of the power conversion circuit 4 similar to the PWM control method of the comparative example. Become. In other words, when the pulse stop control unit 9 that is controlled by the microcomputer is configured by software, the configuration of the power conversion circuit 4 of the comparative example is not changed, and the power converter 1a is not added without adding new hardware. High efficiency can be achieved. Moreover, since the switching operation is stopped near the zero cross of the current of the AC motor 3, an increase in torque pulsation can be suppressed compared to the 150-degree energization method.

<Modification of First Embodiment>
Here, as a modification of the first embodiment, a case where the phase pulse stop section δ is only one of the one cycle sections and a case where the phase of the phase pulse stop section is in a fixed state will be described. FIG. 7 is a waveform diagram showing a relationship between an AC voltage, an AC current and a pulse signal flowing through the electric motor, and a phase pulse stop control signal in the power conversion device according to the modification of the first embodiment, with the voltage on the horizontal axis. The phase θv, and the vertical axis represents the levels of voltage, current, pulse signal, and open phase control signal.

  In this modification, a method of setting the phase pulse stop section δ of the pulse stop control unit 9 shown in FIG. 1 only once for one cycle of current (one cycle) will be described. In addition, description is abbreviate | omitted about the content which is common in the power converter device 1a of 1st Embodiment mentioned above.

  When the control device 5a shown in FIG. 1 is realized by an integrated circuit such as a microcomputer, it is preferable to reduce the calculation load of the microcomputer. Therefore, as shown in FIG. 7D, if the pulse stop control unit 9 sets the phase pulse stop section δ only once per current cycle, it is possible to reduce the calculation load of the microcomputer.

  That is, in this modified example, the pulse stop control unit 9 performed by the control of the microcomputer uses the zero cross point φ of the current phase controlled by the vector control as a reference at the phase φ + π (see FIG. 7D), As shown in the equation (2), the phase pulse stop control signal 9A for stopping both the switching signals of the pulse signals GPU + and GPU− during the phase pulse stop period δ is output to the pulse controller 7.

  That is, as can be seen from Equation (2), when φ is the phase difference between voltage and current and δ is the phase pulse stop period (open phase period), the voltage phase θv with respect to the U phase is φ + π−δ. Only when / 2 <θv <φ + π + δ / 2, switching by the pulse signals GPU + and GPU− is stopped only once. In other cases, switching is performed using pulse signals GPU + and GPU−. Note that the phase pulse stop section δ may be set only once per current cycle in the phase difference φ between the voltage and current.

  Thus, by setting the phase pulse stop section δ to be set once per current cycle, it is possible to halve the calculation load of the pulse stop control unit 9 by the microcomputer. Further, by measuring the phase difference φ between the voltage and the current under the load condition to be driven in advance, and setting the phase difference φ between the voltage and the current in the phase pulse stop control signal 9A of the pulse stop control unit 9 as a fixed value. This further reduces the computational load on the microcomputer.

  As described above, the power conversion circuit 4 according to the first embodiment performs PWM control by the switching operation using the pulse signal 7 </ b> A output from the pulse control unit 7, and outputs AC power to the AC motor 3. At this time, the vector control unit 8 outputs the phase information 8A of the current calculated based on the phase current information 6A from the phase current detection unit 6 to the pulse stop control unit 9. Accordingly, the pulse stop control unit 9 outputs a phase pulse stop control signal 9A generated based on the current phase information 8A to the pulse control unit 7. Therefore, the pulse control unit 7 stops the pulse signal 7A in a predetermined section with reference to the zero cross of the current phase of a predetermined phase (for example, U phase) of the power conversion circuit 4. Therefore, the power conversion circuit 4 stops switching near the current zero crossing, so that the switching loss is reduced. As a result, the efficiency of the power conversion device 1a can be improved and distortion of the output current can be reduced.

<< Second Embodiment >>
In the second embodiment, switching between the PWM control method in which the phase pulse stop interval δ is provided as in the first embodiment and the normal PWM control method in which the phase pulse stop interval δ is not provided will be described. That is, in 2nd Embodiment, the power converter device which can switch phase pulse stop area (delta) with driving | running conditions (for example, rotation speed of AC motor) is demonstrated.

FIG. 8 shows a circuit configuration of the PWM control type power converter 11 according to the second embodiment. As shown in FIG. 8, the power converter 11, instead of the phase current detection unit 6 of the power converting apparatus 1a of the first embodiment shown in FIG. 1, the DC bus current detector for detecting a DC bus current I _DC ( A current detection unit) 10. That is, the power converter 11 of the second embodiment is configured such that the DC bus current detection unit 10 outputs DC bus current information (current) 10 </ b> A to the vector control unit 8.

  In FIG. 8, the vector control unit 8 is configured to output current phase information 8 </ b> A calculated by vector control and rotation speed information 8 </ b> B that is the rotation speed of the AC motor 3 to the pulse stop control unit 91. . Thereby, the pulse stop control part 91 of 2nd Embodiment can switch the phase pulse stop area (delta) with an operating condition (namely, rotational speed of AC motor 3). The other configuration contents are the same as those of the power conversion device 1a of the first embodiment shown in FIG.

  FIG. 9 is a characteristic diagram showing a setting example of a phase pulse stop section (open phase section) in the power converter 11 of the second embodiment, where the horizontal axis represents the rotation speed and the vertical axis represents the open phase section δ. . That is, in the power conversion device 11 of the second embodiment, the pulse stop control unit 91 determines the magnitude of the current rotation speed N of the AC motor 3 and a preset rotation speed N1 as shown in FIG. When the current rotational speed N is less than the rotational speed N1, the phase pulse stop control signal 91A in which the phase pulse stop section δ is set is output to the pulse controller 7. When the current rotational speed N is equal to or higher than the rotational speed N1, the phase pulse stop section δ is set to 0, and a phase pulse stop control signal 91A that does not set the phase pulse stop section δ is output to the pulse controller 7.

  In other words, when the current rotational speed N of the AC motor 3 is less than the rotational speed N1, the pulse control unit 7 outputs a pulse signal having a phase pulse stop section δ, and when the rotational speed is equal to or higher than the rotational speed N1, the pulse control unit. 7 outputs a pulse signal without a phase pulse stop section δ.

  In order to suppress excessive fluctuations in the rotational speed and torque of the AC motor 3 when switching the phase pulse stop section δ depending on the operating conditions, the phase pulse stop section δ is set to the rotational speed as shown in FIG. A method of changing from N2 to the rotational speed N3 at a constant change rate may be used. Further, in order to make the switching of the phase pulse stop section δ even smoother, as shown in FIG. 9C, from the rotational speed N2 to the rotational speed N3, the phase pulse is stopped at a non-linear change rate along a predetermined curve. A method of changing the section δ may be used.

Further, instead of switching the phase pulse stop intervals δ based on the rotational speed of the AC motor 3, based on the average value I _DCave the DC-bus current I _DC detected by the DC bus current detection unit 10 in FIG. 8, a phase A configuration may be employed in which the pulse stop interval δ is switched. In this case, the horizontal axis in the characteristic diagrams of FIGS. 9A, 9 _{</ b> B,} and _{9 </ b> C} is read as the DC bus current average value I _DCave instead of the rotational speed N.

  Further, the phase pulse stop section δ may be switched based on the torque τ output from the AC motor 3 instead of switching the phase pulse stop section δ based on the rotation speed of the AC motor 3. In this case, the horizontal axis in the characteristic diagrams of FIGS. 9A, 9 </ b> B, and 9 </ b> C is read as output torque τ instead of the rotational speed N.

As described above, by switching the phase pulse stop section δ according to the operating conditions of the AC motor 3 (the rotational speed N of the AC motor 3, the output torque τ, the DC bus current average value I _DCave, etc.), the AC motor 3 When in the low-speed rotation range, setting the phase pulse stop interval δ enables the power converter to be driven more efficiently than the PWM control method of the comparative example. Further, when the AC motor 3 is in the high speed rotation range, the phase pulse stop section δ is set to 0, and it is possible to smoothly shift to 180-degree energization without setting the phase pulse stop section.

  In addition, when changing to the direction which narrows phase pulse stop area (delta) according to the driving | running condition of AC motor 3, it switches from a predetermined stop area to the state of zero stop area immediately, and it is constant from the predetermined stop area to the state of zero stop area. It can be performed by changing at a rate of change or changing at a non-linear rate of change from a predetermined stop interval to a stop interval zero state.

  In addition, when changing the phase pulse stop section δ in the direction of widening according to the operating conditions of the AC motor 3, the phase is stopped immediately from the stop section zero state to the predetermined stop section. It can be performed by either changing at a change rate or changing at a non-linear change rate from a stop zone zero state to a predetermined stop zone.

<< Third Embodiment >>
3rd Embodiment demonstrates the case where the power converter device 1a of 1st Embodiment or the power converter device 11 of 2nd Embodiment is applied to the compressor drive of an air conditioner.
FIG. 10 illustrates an overall configuration diagram of an air conditioner 100 according to the third embodiment.

  As shown in FIG. 10, the air conditioner 100 according to the third embodiment includes an outdoor unit 101 that exchanges heat with the outside air, an indoor unit 102 that exchanges heat with the indoor atmosphere, and the outdoor unit 101 and the indoor unit 102. And a pipe 103 to be connected.

  The outdoor unit 101 includes a compressor 104 that compresses refrigerant, a compressor drive motor 105 that drives the compressor 104, an electric motor drive device 106 that drives and controls the compressor drive motor 105, and outside air and heat using the compressed refrigerant. It is comprised with the heat exchanger 107 which performs exchange. Here, the electric power drive device 106 uses the power conversion device 1a of the first embodiment or the power conversion device 11 of the second embodiment. The indoor unit 102 includes a heat exchanger 108 that exchanges heat with the room and a blower 109 that blows air into the room.

  Here, the efficiency of the compressor drive motor 105 will be described with reference to FIG. FIG. 11 is a characteristic diagram showing the relationship of efficiency with respect to the rotational speed of the compressor drive motor 105 in the air conditioner 100 shown in FIG. 10, the horizontal axis shows the rotational speed of the compressor drive motor 105, and the vertical axis shows the compressor. The efficiency of the drive motor 105 is shown.

  When applying PWM control to the motor drive device 106, if the rotational speed of the compressor drive motor 105 is N4 or higher, field weakening control is performed in a voltage saturation region exceeding the voltage that can be output by the sine wave modulation method of the power conversion circuit 4. By reducing the current of the field coil by causing the reactive current to flow, stable driving in the high speed rotation region of the compressor drive motor 105 can be realized. However, since such field weakening control is performed, the efficiency is reduced in the high speed rotation region (rotation speed N4 or more) of the compressor drive motor 105 as shown by the solid line in FIG.

  Therefore, in the third embodiment, for example, the power conversion device 1a of the first embodiment is applied to the air conditioner 100, and the pulse signal 7A in which the phase pulse stop section δ is provided from the pulse control unit 7 to the pulse stop control unit 9 is provided. Is output to control the power conversion circuit 4. In other words, since the number of times of switching of the power conversion circuit 4 can be reduced by providing the phase pulse stop section δ, the loss of the motor driving device 106 can be reduced as a result.

  In this way, by reducing the switching loss of the power conversion circuit 4, the rotational speed at which the efficiency of the motor driving device 106 for driving the compressor driving motor 105 reaches its peak as shown by the one-dot chain line characteristic in FIG. It is possible to improve the efficiency in a region where the rotation speed is lower than N4. In the voltage saturation region where the rotational speed is N4 or higher, the pulse stop controller 9 in FIG. 1 outputs a pulse signal with the phase pulse stop interval δ set to 0, and switches to the 180-degree energization PWM control method to weaken it. It is possible to drive the field control region.

  As described above, according to the third embodiment, the number of switching operations of the power conversion circuit 4 can be reduced with the configuration of the power conversion circuit 4 similar to that of the PWM control method of the comparative example. When the control unit 9 is configured by software, it is possible to realize high efficiency of the air conditioner 100 without adding hardware.

  The power converters 1a, 11 according to the present invention, the motor drive device 106 using the power converters 1a, 11 and the air conditioner 100 using the motor drive device 106 have been specifically described. Needless to say, the present invention is not limited to the contents of the above-described embodiments, and various modifications can be made without departing from the scope of the invention.

  That is, the present invention is not limited to the contents of the first to third embodiments, and various modifications can be made. In other words, the above-described embodiments are illustrated in detail in order to easily understand the contents of the present invention, and are not necessarily limited to those having all the configurations described above. Further, a part of the configuration of an embodiment can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of an embodiment.

  Moreover, it is also possible to add, delete, and replace the configuration of the other embodiment with respect to a part of the configuration of each embodiment. Furthermore, each of the above-described configurations, functions, processing units, processing means, and the like may be realized by hardware by designing a part or all of them with, for example, an integrated circuit. Each of the above-described configurations, functions, and the like may be realized by software by having a processor interpret and execute a program that realizes each function. Information such as programs, tables, and files for realizing each function is stored in a memory, a hard disk, a recording device such as an SSD (Solid State Drive), an IC (integrated circuit) card, an SD card, a DVD (Digital Versatile Disc). Etc. can be placed on a recording medium. Further, the control lines and information lines indicate what is considered necessary for the explanation, and not all the control lines and information lines on the product are necessarily shown. Actually, it may be considered that almost all the components are connected to each other.

  According to the present invention, not only a power conversion device that drives an electric motor used in an air conditioner but also an electric power conversion device that drives an electric motor used in household appliances such as a refrigerator, a washing machine, and a vacuum cleaner, etc. are effectively used. can do.

1a, 11 Power converter 2 DC power source 3 AC motor (motor)
4 Power Conversion Circuit 41 Power Conversion Main Circuit 42 Gate Driver 5a Control Device 6 Phase Current Detection Unit (Current Detection Unit)
7 Pulse control unit 8 Vector control unit 9, 91 Pulse stop control unit 10 DC bus current detection unit (current detection unit)
6A Phase current information (current)
7A Pulse signal 8A Phase information (current phase)
8B Rotational speed information 9A, 91A Phase pulse stop control signal (pulse stop control signal)
10A DC bus current information (current)
V ^* Applied voltage command (command voltage)
δ phase pulse stop section 100 Air conditioner 101 Outdoor unit 102 Indoor unit 103 Piping 104 Compressor 105 Compressor drive motor 106 Motor drive unit 107, 108 Heat exchanger 109 Blower

Claims (13)

A power conversion device that performs power conversion for driving an electric motor by PWM control using a vector control method,
A pulse control unit for outputting a pulse signal for performing the PWM control;
A power conversion circuit configured to include a switching element having a three-phase configuration and using the pulse signal output from the pulse control unit to convert DC power to AC power;
A current detection unit for detecting a current of the power conversion circuit;
A vector control unit that performs vector control based on the current detected by the current detection unit and generates a command voltage to the pulse control unit;
In order to stop the positive-side and negative-side switch elements of a predetermined phase of the power conversion circuit, the pulse signal of a section determined with reference to the current phase of the power conversion circuit is passed over the determined section. generates Rupa pulse stop control signal is stopped, the power conversion apparatus characterized by comprising a pulse stop control section for outputting a pulse stop control signal to the pulse control unit. The pulse stop control unit
For each predetermined phase, a pulse stop control signal is generated to stop the pulse signal in the predetermined section over the predetermined section, and the pulse stop control signal is output to the pulse control unit The power conversion device according to claim 1, wherein: The power converter according to claim 2, wherein the pulse signal in the predetermined section is a pulse signal in a section including a zero-cross point of a current flowing in the power conversion circuit. The pulse stop control unit
Wherein one or two times a cycle period of the current flowing through the power conversion circuit, a power converter according to billed to claim 2 you and generates the pulse stop control signal. The pulse stop control unit
In the power conversion circuit, a DC bus current information, the AC output current information, and the AC output frequency information, based on at least one information out of the which it is possible to change the stop section of the pulse signal at a predetermined rate The power converter according to claim 2, wherein a pulse stop control signal is generated. The pulse stop control unit
In the power conversion circuit, a DC bus current information, the AC output current information, and the AC output frequency information, based on at least one information among, switching the switch period of said pulse signal between zero and the predetermined section The power converter according to claim 2, wherein the pulse stop control signal is generated. An electric motor drive device driven by a power conversion device that performs power conversion for driving an electric motor by PWM control using a vector control method,
The power converter is
A pulse control unit for outputting a pulse signal for performing the PWM control;
A power conversion circuit configured to include a switching element having a three-phase configuration and using the pulse signal output from the pulse control unit to convert DC power to AC power;
A current detection unit for detecting a current of the power conversion circuit;
A vector control unit that performs vector control based on the current detected by the current detection unit and generates a command voltage to the pulse control unit;
In order to stop the positive-side and negative-side switch elements of a predetermined phase of the power conversion circuit, the pulse signal of a section determined with reference to the current phase of the power conversion circuit is passed over the determined section. It generates Rupa pulse stop control signal is stopped, and a pulse stop control section for outputting a pulse stop control signal to the pulse control unit,
An electric motor driving apparatus for driving an electric motor with AC power output from the power conversion circuit. The pulse stop control unit
Depending on the operating conditions of the motor, for each of the predetermined phase, to generate the pulse stop control signal for changing the stop section of the pulse signal in the section including the zero-crossing point of the current flowing through the power conversion circuit The electric motor drive device according to claim 7 . The operating condition of the electric motor is at least one operating state among a rotational speed of the electric motor, an output torque of the electric motor, a DC bus current of the power conversion circuit, an AC output current, and an AC output frequency. The electric motor drive device according to claim 8 . The pulse stop control unit
Changing the stop period of the pulse signal,
Immediately switch from a predetermined stop section to a stop section zero state,
Change from a predetermined stop section to a stop section zero state at a constant rate of change,
Change from a predetermined stop section to a stop section zero state at a non-linear change rate,
The motor driving device according to claim 8, wherein the motor driving device is performed by any one of the following. The pulse stop control unit
Changing the stop period of the pulse signal,
Immediately switch from the stop zone zero state to the predetermined stop zone,
Change from a stop zone zero state to a predetermined stop zone at a constant rate of change,
Change from a stop zone zero state to a predetermined stop zone at a non-linear rate of change,
The motor driving device according to claim 8, wherein the motor driving device is performed by any one of the following. The electric motor drive device according to claim 8 , wherein the pulse train of the pulse signal has an asymmetric ON / OFF duty waveform before and after the stop period of the pulse signal. The motor driving device according to any one of claims 7 a stone claim 12, and characterized in that the drive control of the compressor drive motor for driving a compressor for compressing a refrigerant for performing outside air heat exchange Air conditioner to do.

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