JP5961949B2 - Power converter - Google Patents

Description

  The present invention relates to a power conversion device that converts input power to predetermined power by switching.

  In a motor used for an electric compressor of an air conditioner or the like, a harmonic component such as a five-fold component or a seven-fold component of the fundamental frequency may be included in the induced voltage. In the conventional control, the inverter circuit that supplies power to the motor is controlled so that the phase current flowing through the motor becomes a sine wave. However, this control may cause problems such as distortion of the motor current due to the influence of motor voltage distortion, and torque ripple.

  Therefore, a technique has been proposed in which a compensation voltage component that cancels out the torque ripple of the motor is prepared in advance in a table, and this compensation voltage is added to the voltage command to reduce the torque ripple (see, for example, Patent Document 2).

  On the other hand, in a so-called capacitorless inverter (see, for example, Patent Document 1), in an inverter that does not have an energy storage element therein, when torque ripple occurs, the harmonic component is also included in the energy input to the inverter. Therefore, there arises a problem that the power supply harmonic regulation cannot be satisfied. Therefore, a technique for reducing current distortion and torque ripple by separately controlling the harmonic component of the motor current has been proposed (see, for example, Patent Document 3).

JP 2002-51589 A JP 2008-219966 A JP 2006-262700 A

  However, in the example of Patent Document 3, when the ripple frequency to be reduced is high, such as when the motor rotates at high speed, a general-purpose control CPU cannot obtain a sufficient control band, and conversely increases harmonic components. May cause problems. Although it is conceivable to use a high-performance CPU, this increases the cost.

  The present invention has been made paying attention to the above-described problem, and an object of the present invention is to prevent an increase in power supply harmonics caused by motor voltage distortion in a power converter.

In order to solve the above-mentioned problem, the first invention
A switching element (Su, Sv, Sw, Sx, Sy, Sz) is provided, the AC power supplied from the AC power source (6) is converted into AC power of a predetermined voltage and frequency, and the connected motor (7 Power conversion device to supply to
A control unit (5) for controlling switching of the switching element ;
A converter circuit (2) for full-wave rectification of the power supply voltage (vin) of the AC power supply (6);
A DC link section (3) having a capacitor (3a) connected in parallel to the output of the converter circuit (2) and outputting a pulsating DC voltage (vdc);
An inverter circuit (4) for switching the output of the DC link part (3) to convert to AC and supplying the connected motor (7) ;
The control unit (5) includes a current control unit (53) that controls the current of the motor (7), and a harmonic component removal unit (52 that reduces harmonic components input to the current control unit (53). ), And the switching is controlled so that the current (iu, iv, iw) of the motor (7) pulsates in synchronization with the pulsation of the power supply voltage (vin) .

In this configuration, since the harmonic component removal unit (52) reduces the harmonic component input to the current control unit (53), a signal with the reduced harmonic component is input to the current control unit (53). Become .

In this configuration, in a so-called capacitor-less inverter circuit, so that the signal having reduced harmonic components are an input current control unit (53).

In addition, the second invention,
In the power converter of the first invention ,
The harmonic component removal unit (52) includes an input current (iin), an actual current value (id, iq) of the motor (7), a current command value (id ^* , iq ^* ) of the motor (7), and the It functions for at least one of the deviation between the actual current value (id, iq) and the current command value (id ^* , iq ^* ).

In this configuration, the input current (iin), the actual current value (id, iq), the current command value (id ^* , iq ^* ), the actual current value (id, iq) and the current command value (id ^*) , iq ^* ) and the like are reduced to higher harmonic components and input to the current controller (53).

In addition, the third invention,
In power conversion device of the first or second aspect of the invention,
The harmonic component removing unit (52) removes a signal in a predetermined frequency region from an input signal to the harmonic component removing unit (52) and outputs the signal.

  In this configuration, a signal in a predetermined frequency region (for example, a signal having a certain frequency or higher) is removed from the input to the current control unit (53).

In addition, the fourth invention is
In power conversion device of the first or second aspect of the invention,
The harmonic component removal unit (52) extracts a signal having a predetermined frequency included in the input signal to the harmonic component removal unit (52) as a removal component to be reduced, and the input signal The removal component is subtracted.

  In this configuration, a signal having a predetermined frequency (for example, a sixth-order component of the voltage of the motor (7)) is removed from the input to the current control unit (53).

In addition, the fifth invention,
In the power converter of the fourth invention,
The harmonic component removing unit (52) extracts the removed component by Fourier transform.

  In this configuration, since the removal component is extracted by Fourier transform, the target removal component can be accurately extracted.

In addition, the sixth invention,
In the power conversion device of the fourth or fifth invention,
The harmonic component removing unit (52) corrects the removed component so that the harmonic component contained in the subtracted signal subjected to the subtraction is reduced.

  In this configuration, the removal component is corrected according to the subtraction result.

In addition, the seventh invention,
In power conversion device of the first or second aspect of the invention,
The harmonic component removing unit (52) is characterized in that the harmonic component is reduced by Fourier-transforming a state quantity input to the harmonic component removing unit (52).

  In this configuration, since the harmonic component is extracted by Fourier transform, the target frequency component can be accurately extracted.

Further, the eighth invention is
In the power converter of the fifth or seventh invention,
The harmonic component removing unit (52) performs Fourier transform based on a period that is an integral multiple of a half cycle of the AC power supply (6).

  In this configuration, the magnitude of the harmonic component of the target frequency can be accurately grasped by performing the Fourier transform for a period that is an integral multiple of a half cycle of the AC power supply (6).

In addition, the ninth invention,
In any one of the power converters of the first to eighth inventions,
The harmonic component includes a frequency component obtained by multiplying the fundamental frequency of the voltage of the motor (7) by 6n (n is an integer).

  In this configuration, a relatively high frequency component can be extracted as the harmonic component.

The tenth aspect of the invention is
In any one of the power converters of the first to ninth inventions,
The harmonic component removal unit (52) changes the removal amount of the harmonic component according to any of the rotational speed, torque, and electric power of the motor (7).

  In this configuration, it is possible to change the removal amount of the harmonic component by following the operating state.

  According to the first aspect of the invention, since the signal with the reduced harmonic component is input to the current control unit (53), the power converter is configured not to increase the power supply harmonic caused by the motor voltage distortion. Is possible.

Further, according to the first invention, in the so-called capacitorless inverter circuit, it is possible to prevent the power source harmonics caused by the motor voltage distortion from increasing.

According to the second invention, the input current (iin), the actual current value (id, iq), the current command value (id ^* , iq ^* ), the actual current value (id, iq) and the Since the harmonic component is removed from at least one of the deviations of the current command value (id ^* , iq ^* ), it is possible to prevent the power supply harmonic caused by the motor voltage distortion from increasing.

According to the third aspect of the invention, since the signal in which the component in the predetermined frequency region is reduced is input to the current control unit (53), in the power conversion device, the power supply in the frequency region caused by motor voltage distortion It becomes possible not to increase the harmonics.

According to the fourth aspect of the invention, since the signal in which the predetermined frequency component is reduced is input to the current control unit (53), the power converter has a power supply at the frequency caused by motor voltage distortion. It becomes possible not to increase the harmonics.

Further, according to the fifth aspect , since the target frequency component can be accurately extracted, it is possible to more reliably suppress an increase in power supply harmonics.

According to the sixth aspect of the invention, the removal component is corrected, so that the harmonic component can be more reliably reduced.

Further, according to the seventh aspect , since the target frequency component can be accurately extracted, it is possible to more reliably suppress an increase in power supply harmonics.

Further, according to the eighth invention, since the magnitude of the harmonic component of the target frequency can be accurately grasped, it is possible to more reliably suppress an increase in the power supply harmonic.

Further, according to the ninth aspect , since a relatively high frequency component can be extracted as the harmonic component, it is possible to more reliably suppress an increase in power supply harmonics.

According to the tenth aspect , even if the operating state changes, it is possible to more reliably suppress an increase in power harmonics.

FIG. 1 is a block diagram showing a configuration of a power converter according to an embodiment of the present invention. FIG. 2 is a block diagram illustrating a configuration example of the control unit. FIG. 3 is a block diagram illustrating a configuration example of the current command generation unit. FIG. 4 is a block diagram illustrating a configuration example of the harmonic component removing unit. FIG. 5 is a block diagram illustrating a configuration example of the voltage distortion correction unit. FIG. 6 is a flowchart for explaining the compensation voltage operation performed by the voltage distortion correction unit. FIG. 7A is a waveform diagram showing motor input power, U-phase phase voltage, and motor current when no compensation voltage is superimposed. FIG. 7B is a waveform diagram showing input power, phase voltage, and motor current when the compensation voltage is superimposed. FIG. 8 is a block diagram illustrating a configuration example of the matrix converter. FIG. 9 is a block diagram illustrating a configuration example of the power conversion device when a three-phase AC power source is used as the AC power source.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. The following embodiments are essentially preferable examples, and are not intended to limit the scope of the present invention, its application, or its use.

"overall structure"
FIG. 1 is a block diagram showing a configuration of a power conversion device (1) according to an embodiment of the present invention. As shown in the figure, the power converter (1) includes a converter circuit (2), a DC link unit (3), an inverter circuit (4), and a control unit (5), and a single-phase AC power source (6). The AC power supplied from is converted into power of a predetermined frequency and supplied to the motor (7). In addition, the motor (7) of this embodiment is a three-phase alternating current motor, and is for driving the compressor provided in the refrigerant circuit of the air conditioner. More specifically, the motor (7) is a 4-pole 6-slot concentrated winding motor. In this motor (7), the harmonic components of the induced voltage tend to include many fifth and seventh order components of the fundamental wave. The harmonic component based on the motor voltage distortion also appears in the power supply current and DC link voltage (described later).

<Converter circuit (2)>
The converter circuit (2) is connected to the AC power source (6) via the reactor (L), and full-wave rectifies the AC output from the AC power source (6) to DC. In this example, the converter circuit (2) is a diode bridge circuit in which a plurality (four in the present embodiment) of diodes (D1 to D4) are connected in a bridge shape. These diodes (D1 to D4) perform full-wave rectification on the AC voltage of the AC power supply (6) and convert it to a DC voltage.

<DC link (3)>
The DC link part (3) includes a capacitor (3a). The capacitor (3a) is connected in parallel to the output of the converter circuit (2), and the DC voltage (DC link voltage (vdc)) generated across the capacitor (3a) is connected to the input node of the inverter circuit (4). ing. The capacitor (3a) is constituted by, for example, a film capacitor. This capacitor (3a) has a capacitance capable of smoothing only the ripple voltage (voltage fluctuation) generated corresponding to the switching frequency when the switching element (described later) of the inverter circuit (4) performs switching operation. ing. That is, the capacitor (3a) is a small-capacitance capacitor that does not have a capacitance that smoothes the voltage rectified by the converter circuit (2) (voltage fluctuation caused by the power supply voltage). Therefore, the DC link voltage (vdc) output from the DC link unit (3) has a large pulsation such that the maximum value is twice or more the minimum value.

<Inverter circuit (4)>
The inverter circuit (4) has an input node connected in parallel to the capacitor (3a) of the DC link section (3), and switches the output of the DC link section (3) to convert it to three-phase AC, and is connected to the motor (7) to supply. The inverter circuit (4) of the present embodiment is configured by a plurality of switching elements being bridge-connected. Since this inverter circuit (4) outputs three-phase alternating current to the motor (7), it has six switching elements (Su, Sv, Sw, Sx, Sy, Sz). Specifically, the inverter circuit (4) includes three switching legs formed by connecting two switching elements in series with each other, and in each switching leg, an upper arm switching element (Su, Sv, Sw) and a lower arm switching element. The midpoints of (Sx, Sy, Sz) are respectively connected to coils (not shown) of each phase of the motor (7). In addition, free-wheeling diodes (Du, Dv, Dw, Dx, Dy, Dz) are connected in antiparallel to each switching element (Su, Sv, Sw, Sx, Sy, Sz). The inverter circuit (4) switches the DC link voltage (vdc) input from the DC link unit (3) by turning on and off these switching elements (Su, Sv, Sw, Sx, Sy, Sz). Convert to phase AC voltage and supply to motor (7). The control unit (5) controls the on / off operation.

<Control part (5)>
The control unit (5) performs switching in the inverter circuit (4) so that the current flowing through the motor (7) (motor current (iu, iv, iw)) pulsates in synchronization with the pulsation of the power supply voltage (vin). (ON / OFF operation) is controlled. That is, the power converter (1) is an example of a so-called capacitorless inverter. FIG. 2 is a block diagram illustrating a configuration example of the control unit (5). In this example, the control unit (5) includes a speed control unit (50), a current command generation unit (51), a harmonic component removal unit (52), a dq-axis current control unit (53), and a voltage distortion correction unit (54 ) And a PWM calculation unit (55).

-Speed control unit (50)-
The speed controller (50) obtains a deviation between the rotation angle frequency (ωm) of the mechanical angle of the motor (7) and the command value (ωm ^* ) of the mechanical angle, and proportional / integral calculation (PI calculation) to the deviation. ) To output the torque command value (T ^* ) to the current command generator (51).

-Current command generator (51)-
FIG. 3 is a block diagram illustrating a configuration example of the current command generation unit (51). As shown in the figure, the current command generation unit (51) includes a fundamental wave component calculation unit (51a), an absolute value calculation unit (51b) (abbreviated as abs in FIG. 3), an input current control unit (51c), A dq current command value generation unit (51d), a multiplier (51e, 51f), and an adder (51g) are provided. The torque command value (T ^* ) and the sine value of the phase angle (θin) of the power supply voltage (vin) ( sin (θin)) and the absolute value (| iin |) of the input current (iin).

  In this current command generation unit (51), the fundamental wave component calculation unit (51a) performs a Fourier transform for a period that is an integral multiple of a half cycle of the AC power supply (6), and calculates the power supply from the absolute value of the input current (iin). The fundamental wave component of the voltage is extracted. Thus, it becomes possible to appropriately extract a desired frequency component by setting the Fourier transform to an integral multiple of a half cycle of the AC power supply (6). In this example, specifically, the fundamental wave component calculation unit (51a) sets twice the value obtained by averaging the product of sin (θin) and the input current (iin) as the first value (iin_1st). Looking for.

The absolute value calculation unit (51b) obtains the absolute value of sin (θin). The multiplier (51e) obtains a command value (| iin ^* |) of the absolute value of the input current by multiplying the absolute value of sin (θin) by the first value (iin_1st).

The input current controller (51c) commands the deviation between the absolute value of the input current (iin) (| iin ^* |) and the absolute value of the input current (iin) (| iin |) to be small. Generate a value.

The multiplier (51f) multiplies the absolute value of sin (θin) and the torque command value (T ^* ). This multiplication result pulsates at a frequency twice the power supply frequency. The multiplication result is input to the adder (51g). The adder (51g) adds the output of the multiplier (51f) and the command value output from the input current control unit (51c). The addition result is input to the dq current command value generation unit (51d) as a current command value (idq ^* ).

The dq current command value generation unit (51d) calculates a d-axis current command value (id ^* ) and a q-axis current command value (iq) from a current command value (idq ^* ) and a current phase command value (β ^* ) described later. ^* ) Is obtained and output to the harmonic component removal unit (52). Specifically, the dq current command value generation unit (51d) multiplies the current command value (idq ^* ) by a negative sine value (−sin β ^* ) of a predetermined value (β ^* ) and a cosine value (cos β ^* ). Thus, a d-axis current command value (id ^* ) and a q-axis current command value (iq ^* ) are generated. Here, β ^* is a command value of the phase β of the current flowing through the motor (7).

-Harmonic component removal unit (52)-
The harmonic component removing unit (52) reduces the harmonic component based on the motor current distortion from the input signal. As shown in FIG. 2, the harmonic component removal unit (52) is provided at two locations. In FIG. 2 and the like, branch numbers (−1, 2) are added to the reference numerals to distinguish the two. FIG. 4 is a block diagram illustrating a configuration example of the harmonic component removing unit (52). FIG. 4 illustrates the harmonic component removal unit (52-1) connected to the current command generation unit (51). The current command value (id ^* , iq ^* ) is input to the harmonic component removal unit (52-1). The harmonic component removal unit (52-2) removes harmonic components when the input signal is the deviation between the current command value (id ' ^* , iq' ^* ) and the actual current value (id, iq). Part (52-1).

In the harmonic component removal unit (52-1), the Fourier transform is performed based on a period that is an integral multiple of a half cycle of the AC power supply (6) to obtain the motor (7) from the current command value (id ^* , iq ^* ). The sixth-order component of the voltage is extracted. Specifically, the harmonic component removing unit (52-1) calculates the product of the d-axis current command value (id ^* ) and sin (6θ) and the product of the d-axis current command value (id ^* ) and cos (6θ). A value twice the averaged value is obtained, and the product of the value and sin (6θ) and cos (6θ) is added to obtain the sixth-order component (id_6th ^* ) of the d-axis current command value (id ^* ). Here, θ is the phase of the fundamental wave component of the voltage of the motor (7). The harmonic component removal unit (52-1) outputs a value obtained by subtracting the sixth-order component (id_6th ^* ) from the d-axis current command value (id ^* ). That is, twice the value of the averaged value of the id ^* × sin6θ and Id_sin6shita, When id_cos6θ twice the value of the averaged value of the id ^* × cos6θ, id_6th ^* can be expressed as follows.

id_6th ^* = id_sin6θ × sin6θ + id_cos6θ × cos6θ
The harmonic component removal unit (52-1) adds the product of the q-axis current command value (iq ^* ) and sin (6θ) and the product of the q-axis current command value (iq ^* ) and cos (6θ). Then, a value twice the averaged value is obtained, and the product of that value and sin (6θ) and cos (6θ) is added to obtain the sixth-order component (iq_6th ^* ) of the q-axis current command value (iq ^* ). . The harmonic component removal unit (52-1) outputs a value obtained by subtracting the sixth-order component (iq_6th ^* ) from the q-axis current command value (iq ^* ).

  The harmonic component based on the motor current distortion has a frequency component that is 6n times (n is an integer) the fundamental frequency (basic frequency phase (θ)) of the voltage of the motor (7).

-Dq axis current controller (53)-
The dq axis current control unit (53) is an example of the current control unit of the present invention. The dq-axis current control unit (53) is configured so that the deviation between the command value (id ' ^* , iq' ^* ) of the motor current (iu, iv, iw) and the actual current value (id, iq) is small. A command value (vd ^* , vq ^* ) is generated.

-Voltage distortion correction section (54)-
The control unit (5) compensates for the voltage command values (vd ^* , vq ^* ) to the inverter circuit (4) so that harmonic components (described later) contained in the power supply side based on motor voltage distortion are reduced. The value (compensation voltage (vd_h, vq_h) described later) is adjusted. The voltage distortion correction unit (54) generates this compensation voltage (vd_h, vq_h).

  FIG. 5 is a block diagram illustrating a configuration example of the voltage distortion correction unit (54). As shown in the figure, the voltage distortion correction unit (54) includes a phase adjustment unit (54a), a gain adjustment unit (54b), and a multiplier (54c). The voltage distortion correction unit (54) has a signal (a harmonic based on the motor voltage distortion) having a frequency 6 times the fundamental wave component of the induced voltage included in the DC link voltage (vdc) (that is, a frequency 6 times the fundamental frequency). Wave component). Specifically, the voltage distortion correction unit (54) obtains a frequency component that is six times the fundamental frequency by Fourier transforming the DC link voltage (vdc). Further, ωφ is input to the voltage distortion correction unit (54). This ωφ is a no-load induced voltage.

  The gain adjustment unit (54b) adjusts the gain of ωφ (hereinafter referred to as voltage amplitude (Vh)).

  The phase adjustment unit (54a) detects the phase (δ) of the six-fold frequency component of the fundamental voltage component of the motor voltage included in the DC link voltage (vdc), adjusts the phase (described later), and outputs the result. The output of the phase adjustment unit (54a) is added to 6θ. Thereby, (6θ + δ) is calculated.

The voltage distortion correction unit (54) calculates the product of −sin (6θ + δ) and the voltage amplitude (Vh), and generates a d-axis compensation voltage (vd_h) for correcting the d-axis voltage command value (vd ^* ). . The voltage distortion correction unit (54) calculates the product of −cos (6θ + δ) and the voltage amplitude (Vh), and generates a q-axis compensation voltage (vq_h) for correcting the q-axis voltage command value (vq ^* ). . In this example, each compensation voltage (vd_h, vq_h) has a frequency component of 6n times (n is an integer) the fundamental frequency (basic frequency phase (θ)) of the voltage of the motor (7). . The d-axis compensation voltage (vd_h) and q-axis compensation voltage (vq_h) are added to the d-axis voltage command value (vd ^* ) and q-axis voltage command value (vq ^* ) output from the dq-axis current controller (53), respectively. Then, the new d-axis voltage command value (vd ′ ^* ) and the q-axis voltage command value (vq ′ ^* ) are output to the PWM calculation unit (55). That is, the voltage command value (vd ′ ^* , vq ′ ^* ) output to the PWM calculation unit (55) is compensated according to the harmonic component. In the present embodiment, the compensation voltage (vd_h, vq_h) is changed so that the harmonic component based on the motor voltage distortion included on the power supply side is reduced. More specifically, the value of the phase (δ) is adjusted as will be described later.

-PWM operation part (55)-
The PWM calculation unit (55) includes a d-axis voltage command value (vd ' ^* ), a q-axis voltage command value (vq' ^* ), a DC link voltage (vdc), and a rotor of the motor (7) (not shown) ) Rotation angle (electrical angle (θe)). Based on these values, the PWM calculation unit (55) generates a gate signal (G) that controls the on / off operation of each switching element (Su, Sv, Sw, Sx, Sy, Sz).

<Operation of power converter (1)>
<Overview>
In the present embodiment, since the small-capacitance capacitor (3a) is provided in the DC link section (3), the DC link voltage (vdc) pulsates more greatly. Due to the pulsation of the DC link voltage (vdc), the current conduction width of the diodes (D1 to D4) of the converter circuit (2) becomes wider, and as a result, the power factor is improved. The control unit (5) controls switching in the inverter circuit (4) so that the motor current (iu, iv, iw) pulsates in synchronization with the pulsation of the power supply voltage (vin).

<Operation of control unit (5)>
In the present embodiment, the harmonic component removal unit (52) of the control unit (5) reduces the harmonic component based on the motor current distortion that is input to the dq-axis current control unit (53). Specifically, the harmonic component removal unit (52-1) performs a Fourier transform for a period that is an integral multiple of a half cycle of the AC power supply (6), and uses the current command value (id ^* , iq ^* ) as the motor ( Extract the 6th-order component of the voltage of 7). Then, the harmonic component removal unit (52-1) subtracts the sixth-order component (id_6th ^* , iq_6th ^* ) extracted from the current command value (id ^* , iq ^* ) to obtain a new current command value (id ′ ^* , iq ' ^* ) is generated. Thereby, the signal which reduced the harmonic component based on motor current distortion is input into a dq axis current control part (53).

In the present embodiment, the voltage distortion correction unit (54) obtains the compensation voltage (vd_h, vq_h) and compensates the voltage command value (vd ^* , vq ^* ) with the compensation voltage (vd_h, vq_h). Therefore, the output voltage of the inverter circuit (4) is compensated according to the harmonic component based on the motor voltage distortion. In this embodiment, the amount of compensation is adjusted while detecting a harmonic component based on motor voltage distortion. FIG. 6 is a flowchart illustrating the compensation voltage operation performed by the control unit (5). The control unit (5) adjusts the compensation voltage (vd_h, vq_h) according to the increase or decrease of the harmonic component based on the motor voltage distortion before and after the compensation voltage (vd_h, vq_h) is changed. Specifically, the control unit (5) adjusts the phase (δ) by the so-called hill-climbing method.

  First, in step (S01), the voltage distortion correction unit (54) extracts a harmonic component based on the motor voltage distortion. In step (S02), the control unit (5) compares the harmonic component based on the motor voltage distortion extracted in step (S01) with the previously extracted harmonic component based on the motor voltage distortion. Then, increase / decrease in the harmonic component based on the motor voltage distortion is determined. When the harmonic component based on the motor voltage distortion increases, the process proceeds to step (S03), and when not increased, the process proceeds to step (S04). In step (S03), the control unit (5) controls the phase adjustment unit (54a) to delay the phase (δ), and in step (S04), advances the phase (δ). Thereafter, the control unit (5) proceeds to step (S05) and delays the phase (δ). The amount of phase change at step (S05) is larger than the amount of change at step (S03) or step (S04).

  In step (S06), the voltage distortion correction unit (54) again extracts harmonic components based on the motor voltage distortion. In step (S07), the control unit (5) compares the harmonic component extracted in step (S06) with the harmonic component based on the motor voltage distortion extracted before the phase (δ) adjustment. Thus, the increase / decrease in the harmonic component based on the motor voltage distortion is determined. When the harmonic component based on the motor voltage distortion increases, the process proceeds to step (S08), and when not increased, the process proceeds to step (S09). In step (S08), the control unit (5) controls the phase adjustment unit (54a) to advance the phase (δ), and in step (S09), delays the phase (δ). Thereafter, the control unit (5) proceeds to step (S10) and advances the phase (δ). By varying the phase (δ) in this way, it is possible to search for the phase (δ) in which the harmonic component based on the motor voltage distortion is reduced.

<Effect in this embodiment>
7A and 7B are waveform diagrams for explaining the effect of correction by the voltage distortion correction unit (54). FIG. 7A shows motor input power (p), U-phase phase voltage (vu), U-phase phase current (iu) (motor current) when compensation voltage (vd_h, vq_h) is not superimposed. FIG. FIG. 7B is a waveform diagram showing input power (p), phase voltage (vu), and motor current (iu) when the compensation voltage (vd_h, vq_h) is superimposed. Comparing FIG. 7 (A) and FIG. 7 (B), it can be seen that the motor current (iu) in FIG. 7 (B) has a distorted waveform and includes a harmonic component based on the motor voltage distortion. In this way, the harmonic voltage is included in the motor current (iu) by superimposing the compensation voltages (vd_h, vq_h). When a harmonic component is included in the motor current (iu), as shown in FIG. 7B, distortions in the motor input power, power source current, power, and DC link voltage can be reduced.

  In addition, in the present embodiment, the phase (δ) is searched according to the operating state (rotation speed, load torque, etc.) of the motor (7), so that the harmonic component based on the motor voltage distortion that flows out to the power source is effective. It becomes possible to reduce it. That is, according to the present embodiment, in a so-called capacitorless inverter, it is possible to reduce power supply harmonics caused by motor voltage distortion in accordance with the operating state of the motor.

  In the present embodiment, a signal with reduced harmonic components based on motor current distortion is input to the dq axis current control unit (53). Therefore, it becomes possible to avoid instability of control due to disturbance of harmonics.

<< Other Embodiments >>
The harmonic component based on the motor voltage distortion may be extracted by performing a Fourier transform on the input current to the inverter circuit (4) or by performing a Fourier transform on the input power to the inverter circuit (4). Good.

  The compensation voltage (vd_h, vq_h) may be adjusted by changing the amplitude (voltage amplitude (Vh)) instead of adjusting the phase (δ), or the phase (δ) and the voltage amplitude (Vh). Both of them may be adjusted for adjustment.

  It is also possible to omit either one of the two harmonic component removal units (52-1, 2).

  In addition, the harmonic component removal unit (52-1, 2) changes the removal amount of the harmonic component based on the motor current distortion according to any of the rotation speed, torque, and power of the motor (7). It may be.

  The present invention can also be applied to so-called matrix converters. FIG. 8 is a block diagram illustrating a configuration example of the matrix converter. In this example, nine switching elements (S1, S2,..., S9) connected to a three-phase AC power source (6) are switched to supply a three-phase AC to the motor (7).

  It is also possible to adopt a three-phase AC power source as the AC power source (6). FIG. 9 is a block diagram illustrating a configuration example of the power conversion device (1) when a three-phase AC power source (6) is used as the AC power source. As shown in the figure, the converter circuit (2) is a diode bridge circuit in which six diodes (D1 to D6) are connected in a bridge shape. These diodes (D1 to D6) perform full-wave rectification on the AC voltage of the three-phase AC power supply (6) and convert it to a DC voltage. In the configuration of the converter circuit (2), the frequency of the voltage pulsation of the DC link unit (3) is six times the power supply frequency.

The harmonic component removal unit (52) may remove a signal in a predetermined frequency region from the input signal to the harmonic component removal unit (52) and output the signal. For example, a low-pass filter can be adopted. For example, in the harmonic component removal unit (52-2), a signal in a predetermined frequency region is removed by a low-pass filter for the deviation between the current command value (id ' ^* , iq' ^* ) and the actual current value (id, iq). What is necessary is just to output a thing to a dq axis current control part (53).

  The harmonic component removal unit (52) extracts a signal having a predetermined frequency included in the input signal to the harmonic component removal unit (52) as a removal component to be reduced, and the input signal You may make it subtract the said removal component from. Extraction of a signal having a predetermined frequency can be realized, for example, by performing Fourier transform on an input signal to the harmonic component removing unit (52). As the predetermined frequency, it is conceivable to employ a frequency 6n times (n is an integer) the frequency of the fundamental wave (basic frequency phase (θ)) of the voltage of the motor (7).

  Further, when the harmonic component removal unit (52) is configured to obtain a signal having a predetermined frequency as the removal component, the subtraction signal subjected to the subtraction in the harmonic component removal unit (52) The removal component may be corrected so as to reduce the harmonic component contained in. Specifically, the harmonic component removal unit (52) extracts a harmonic component from the subtracted signal subjected to the subtraction, multiplies the extracted harmonic component by a coefficient, and adds the removed component to the removed component. And the corrected removal component is subtracted from the input signal. The harmonic component may remain in the signal depending on the method for realizing the removal component extraction. By correcting the removal component in this way, the harmonic component can be more reliably reduced.

  INDUSTRIAL APPLICABILITY The present invention is useful as a power conversion device that converts input power to predetermined power by switching.

DESCRIPTION OF SYMBOLS 1 Power converter device 2 Converter circuit 3 DC link part 3a Capacitor 4 Inverter circuit 5 Control part 6 AC power supply 7 Motor 52 Harmonic component removal part 53 dq axis current control part (current control part)

Claims (10)

A switching element (Su, Sv, Sw, Sx, Sy, Sz) is provided, the AC power supplied from the AC power source (6) is converted into AC power of a predetermined voltage and frequency, and the connected motor (7 Power conversion device to supply to
A control unit (5) for controlling switching of the switching element ;
A converter circuit (2) for full-wave rectification of the power supply voltage (vin) of the AC power supply (6);
A DC link section (3) having a capacitor (3a) connected in parallel to the output of the converter circuit (2) and outputting a pulsating DC voltage (vdc);
An inverter circuit (4) for switching the output of the DC link part (3) to convert to AC and supplying the connected motor (7) ;
The control unit (5) includes a current control unit (53) that controls the current of the motor (7), and a harmonic component removal unit (52 that reduces harmonic components input to the current control unit (53). And the switching is controlled so that the current (iu, iv, iw) of the motor (7) pulsates in synchronization with the pulsation of the power supply voltage (vin). apparatus. In the power converter device of Claim 1 ,
The harmonic component removal unit (52) includes an input current (iin), an actual current value (id, iq) of the motor (7), a current command value (id ^* , iq ^* ) of the motor (7), and the A power converter that functions for at least one of a deviation between an actual current value (id, iq) and the current command value (id ^* , iq ^* ). In the power converter of Claim 1 or Claim 2 ,
The said harmonic component removal part (52) removes the signal of a predetermined frequency area | region from the input signal to this harmonic component removal part (52), and outputs it, The power converter device characterized by the above-mentioned. In the power converter of Claim 1 or Claim 2 ,
The harmonic component removal unit (52) extracts a signal having a predetermined frequency included in the input signal to the harmonic component removal unit (52) as a removal component to be reduced, and the input signal A power converter characterized by subtracting a removal component. In the power converter of Claim 4 ,
The harmonic component removing unit (52) extracts the removed component by Fourier transform. In the power converter of Claim 4 or Claim 5 ,
The harmonic component removing unit (52) corrects a removed component so that a harmonic component contained in the subtracted signal subjected to the subtraction is reduced. In the power converter of Claim 1 or Claim 2 ,
The said harmonic component removal part (52) reduces the said harmonic component by Fourier-transforming the state quantity input into this harmonic component removal part (52), The power converter device characterized by the above-mentioned. In the power converter of Claim 5 or Claim 7 ,
The said harmonic component removal part (52) performs a Fourier-transform based on the period of the integral multiple of the half cycle of the said alternating current power supply (6), The power converter device characterized by the above-mentioned. In any one of the power converter of claims 1 to 8,
The power converter according to claim 1, wherein the harmonic component includes a frequency component obtained by multiplying a fundamental frequency of the voltage of the motor (7) by 6n (n is an integer). In any one of the power converter of claims 1 to 9,
The said harmonic component removal part (52) changes the removal amount of the said harmonic component according to either the rotation speed of the said motor (7), a torque, and electric power, The power converter device characterized by the above-mentioned.

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