JP6024262B2 - Power converter - Google Patents

Description

  The present invention relates to a power conversion device that converts input power into predetermined output power by a switching operation, and more particularly to a technique for preventing overvoltage breakdown.

  2. Description of the Related Art Conventionally, there is known a power conversion device that converts an input AC voltage to a DC link voltage by a converter circuit and a DC link unit, and then converts the DC link voltage to an output AC voltage by an inverter circuit. In recent years, a power converter (so-called electrolytic capacitor-less inverter) in which the capacity of a capacitor in a DC link portion is reduced has been studied (for example, Patent Document 1). In a power conversion device in which the capacitor of the DC link unit is reduced in capacity, the input AC voltage rectified in the converter circuit is supplied to the DC link unit, but the output of the converter circuit is hardly smoothed in the DC link unit. The pulsating component corresponding to the frequency of the input AC voltage is included in the DC link voltage. For this reason, in the power conversion device of Patent Document 1, the output torque of the motor is varied so that the pulsation component of the input AC voltage is superimposed on the output torque of the motor.

JP 2008-236354 A

  By the way, in the power converter device like patent document 1, since the output torque of a motor pulsates according to the frequency of input AC voltage, the q-axis current and q-axis voltage of a motor also according to the frequency of input AC voltage. Will pulsate. Therefore, if the time change rate of the q-axis current of the motor increases momentarily during the period when the output torque of the motor decreases, the phase difference between the motor current phase and the voltage phase increases instantaneously. There is a possibility that energy is instantaneously regenerated to the DC link section. Further, in the power conversion device as described above, since the capacitor of the DC link unit is reduced in capacity, the energy instantaneously regenerated from the motor to the DC link unit (hereinafter referred to as instantaneous regenerative energy) is sufficient. It is difficult to absorb. Therefore, it is difficult to protect the inverter circuit from a voltage increase due to instantaneous regenerative energy. Even when the pulsating component of the input AC voltage is not superimposed on the output torque of the motor as in the power conversion device of Patent Document 1, energy may be instantaneously regenerated from the motor to the DC link unit. is there. For example, when the motor load fluctuates greatly, if the motor output torque is fluctuated greatly according to the load fluctuation, the time change rate of the q-axis current of the motor increases momentarily. May end up.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a power converter that can prevent overvoltage breakdown of an inverter circuit due to instantaneous regenerative energy.

A first invention is a converter circuit (11) for rectifying an input AC voltage, and a DC link that receives the output of the converter circuit (11) and generates a DC voltage including a pulsating component according to the frequency of the input AC voltage. Part (12), an inverter circuit (13) that converts the DC voltage from the DC link part (12) into an output AC voltage by switching operation and supplies it to the motor (32), and the current phase of the motor (32) (beta) and such that the difference between the voltage phase ([delta]) falls below a predetermined phase threshold, includes control unit that controls the switching operation of the inverter circuit (13) and (14), the control unit ( 14), the DC voltage (V _dc ) of the DC link part (12) constitutes the inverter circuit (13) by the energy instantaneously regenerated from the motor (32) to the DC link part (12). Does not exceed the breakdown voltage of the element In other words, the phase threshold is adjusted according to the difference between the withstand voltage of the elements constituting the inverter circuit (13) and the DC voltage (V _dc ) of the DC link part (12). It is a power converter device.

In the first aspect of the invention, by controlling the switching operation of the inverter circuit (13) so that the difference between the current phase (β) and the voltage phase (δ) of the motor (32) is equal to or less than the phase threshold, Instantaneous regeneration of energy from (32) to the DC link section (12) can be suppressed. Further, even when the DC voltage of the DC link section (12) increases due to instantaneous regenerative energy, the increased DC voltage can be made lower than the withstand voltage of the elements constituting the inverter circuit (13).

  In a second aspect based on the first aspect, the control unit (14) includes a pulsation component corresponding to the frequency of the input AC voltage in the output torque of the motor (32), and the motor ( 32) is configured to control the switching operation of the inverter circuit (13) so that the difference between the current phase (β) and the voltage phase (δ) is equal to or less than the phase threshold value. It is a power converter.

  In the second aspect of the invention, the motor is controlled by controlling the switching operation of the inverter circuit (13) so that the difference between the current phase (β) and the voltage phase (δ) of the motor (32) is equal to or less than the phase threshold. Instantaneous regeneration of energy from (32) to the DC link section (12) can be suppressed.

  According to a third aspect of the present invention, in the first or second aspect, the control unit (14) controls the current phase (β) of the motor (32) and the voltage phase of the voltage to be applied to the motor (32). A power conversion device configured to limit a voltage phase (δ) of a voltage to be applied to the motor (32) so that a difference from (δ) is equal to or less than the phase threshold value. It is.

In the third aspect of the invention, by limiting the voltage phase (δ) of the voltage to be applied to the motor (32), the difference between the current phase (β) and the voltage phase (δ) of the motor (32) is phase-shifted. It can be made below the threshold .

A fourth invention is a power converter according to any one of the first to third inventions, wherein the phase threshold is set to a value of 90 ° or less.

In the fourth aspect of the invention, since instantaneous regeneration of energy from the motor (32) to the DC link unit (12) can be prevented, the DC voltage of the DC link unit (12) increases due to the instantaneous regenerative energy. This can be prevented.

In a fifth aspect based on the first or second aspect, the control unit (14) causes the difference between the current phase (β) and the voltage phase (δ) of the motor (32) to be less than or equal to a phase threshold value. current command value such as _{^{(i d *, i q *}} ) current command generation unit for generating (104), the current command value generated by the current command generation unit (104) _{^{(i d *, i q *}} ) voltage command value _{^{(V d *, V q *}} ) on the basis of a current control unit for generating (107), the current control unit (107) the voltage command value generated by _{^{(V d *, V q *}} ) in And a PWM calculation unit (109) for controlling the switching operation of the inverter circuit (13) based on the power conversion device.

In the fifth aspect of the invention, the current command value (i _d ^* , i _q ^* ) is generated so that the difference between the current phase (β) and the voltage phase (δ) of the motor (32) is equal to or less than the phase threshold value. Thus, the difference between the current phase (β) and the voltage phase (δ) of the motor (32) can be made equal to or less than the phase threshold value.

  According to a sixth invention, in any one of the first to fifth inventions, the control unit (14) is configured to detect the DC link unit (12) from the breakdown voltage of the elements constituting the inverter circuit (13). DC voltage (V _dc ), The phase threshold value is adjusted such that the phase threshold value increases as the value obtained by subtracting the value increases.

According to the first, second, third and fifth inventions, since instantaneous regeneration of energy from the motor (32) to the DC link section (12) can be suppressed, an inverter using instantaneous regeneration energy The overvoltage breakdown of the circuit (13) can be prevented.

Further, according to the first invention, even if the DC voltage of the DC link part (12) by the instantaneous regenerative energy is increased, the DC voltage after increase than the withstand voltage of the elements constituting the inverter circuit (13) Therefore, overvoltage breakdown of the inverter circuit (13) due to instantaneous regenerative energy can be surely prevented.

According to the fourth invention, it is possible to prevent the DC voltage of the DC link part (12) from rising due to the instantaneous regenerative energy, so that the overvoltage breakdown of the inverter circuit (13) due to the instantaneous regenerative energy is surely prevented. be able to.

The block diagram for demonstrating the structural example of a power converter device. The block diagram for demonstrating the structural example of a control part. The wave form diagram for demonstrating a modulation torque command value. The vector diagram for demonstrating a current vector and a voltage vector. The vector diagram for demonstrating a phase adjustment process. The vector diagram for demonstrating the modification 1 of a phase adjustment process. The wave form diagram for demonstrating the modification 2 of a phase adjustment process. The block diagram for demonstrating the modification 3 of a phase adjustment process.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals, and description thereof will not be repeated.

[Power converter]
FIG. 1 shows a configuration example of a power conversion device (10) according to an embodiment of the present invention. The power converter (10) converts an input AC voltage (in this example, a power supply voltage from a single-phase AC power supply (31)) into a predetermined output AC voltage (in this example, a three-phase AC voltage), and converts the motor into a motor. (32), converter circuit (11), DC link unit (12), inverter circuit (13), control unit (14), power supply phase detection unit (21), input current A detection unit (22), a motor current detection unit (23), a motor rotation speed detection unit (24), and a motor phase detection unit (25) are provided. In this example, the motor (32) is a three-phase AC motor. For example, the motor (32) is a 4-pole 6-slot concentrated winding DC brushless motor, and is used to drive a compressor provided in a refrigerant circuit of an air conditioner.

<Converter circuit>
The converter circuit (11) is connected to the AC power supply (31) via the reactor, and full-wave rectifies the voltage voltage from the AC power supply (31). In this example, the converter circuit (11) includes four diodes (D1, D2, D3, D4) connected in a bridge shape. That is, the converter circuit (11) constitutes a diode bridge circuit.

<DC link part>
The DC link unit (12) has a capacitor (C12) connected in parallel to the output node of the converter circuit (11), and receives the output of the converter circuit (11) to generate a DC link voltage (DC voltage). . In this example, one end of the capacitor (C12) is connected to one output node of the converter circuit (11) via the reactor (L12).

  The DC link voltage generated by the DC link unit (12) includes a pulsation component corresponding to the frequency of the power supply voltage (more specifically, a pulsation component having a frequency twice the frequency of the power supply voltage). Yes. The reason will be described below. The capacitance value of the capacitor (C12) of the DC link unit (12) can hardly smooth the output of the converter circuit (11), while the ripple voltage due to the switching operation of the inverter circuit (13) (switching frequency) Is set so that voltage fluctuations according to Specifically, the capacitor (C12) has a capacitance of about 0.01 times the capacitance value of a smoothing capacitor (for example, an electrolytic capacitor) used for smoothing the output of the converter circuit (11) in a general power converter. It is constituted by a small-capacitance capacitor (for example, a film capacitor) having a value (for example, about several tens of μF). Since the capacitor (C12) is configured in this way, the output of the converter circuit (11) is hardly smoothed in the DC link unit (12). As a result, the pulsation component corresponding to the frequency of the power supply voltage is generated in the DC link. Will remain in the voltage. For example, the DC link voltage pulsates so that its maximum value is twice or more of its minimum value.

<Inverter circuit>
The input node of the inverter circuit (13) is connected in parallel to the capacitor (C12). The inverter circuit (13) converts the DC link voltage from the DC link unit (12) into an output AC voltage (in this example, a three-phase AC voltage) by switching operation, and supplies it to the motor (32). In this example, the inverter circuit (13) has six switching elements (Su, Sv, Sw, Sx, Sy, Sz) and six free-wheeling diodes to supply a three-phase AC voltage to the motor (32). (Du, Dv, Dw, Dx, Dy, Dz). More specifically, the inverter circuit (13) includes three switching legs formed by connecting two switching elements in series with each other. In each of the three switching legs, the upper arm switching element (Su , Sv, Sw) and the midpoint of the switching element (Sx, Sy, Sz) of the lower arm are connected to the coils of each phase (coil of u phase, v phase, w phase) of the motor (32), respectively. Yes. Further, free-wheeling diodes (Du, Dv, Dw, Dx, Dy, Dz) are connected in antiparallel to the switching elements (Su, Sv, Sw, Sx, Sy, Sz), respectively.

<Detection unit>
The power phase detector (21) detects the phase angle (power phase (θ _in )) of the power source voltage of the AC power source (31). The input current detector (22) detects the input current (i _in ) supplied from the converter circuit (11) to the DC link unit (12). The motor current detector (23) detects motor currents (u-phase current (i _u ), v-phase current (i _v ), and w-phase current (i _w )) that flow in each phase of the motor (32). The motor rotation speed detector (24) detects the actual rotation speed (ω) of the motor (32). The motor phase detector (25) detects the phase angle (motor phase (θ _m )) of the rotor of the motor (32).

<Control part>
The control unit (14) combines the output torque of the motor (32) with a pulsation component corresponding to the frequency of the power supply voltage, and the difference between the current phase (β) and the voltage phase (δ) of the motor (32). The switching operation of the inverter circuit (13) (more specifically, the switching elements (Su, Sv, Sw, Sx, Sy, Sz)) is controlled so as to be smaller than a predetermined phase threshold.

<Configuration of control unit>
Next, the configuration of the control unit (14) will be described with reference to FIG. The control unit (14) includes a subtraction unit (101), a speed control unit (102), an input current command calculation unit (103), a current command generation unit (104), a coordinate conversion unit (105), a subtraction Unit (106), a current control unit (107), a phase adjustment unit (108), and a PWM calculation unit (109).

<< Subtraction unit and speed control unit >>
The subtraction unit (101) subtracts the actual rotation speed (ω) detected by the motor rotation speed detection unit (24) from the speed command value (ω ^* ) to calculate a speed deviation value. The speed control unit (102) performs proportional integral calculation (PI calculation) on the speed deviation value obtained by the subtraction unit (101), and averages the load torque of the motor (32) (load torque pulsating at a predetermined cycle). And an average torque command value (T _ave ^* ) indicating the average value of the load torque (average torque) is output.

<Input current command calculation unit>
The input current command calculation unit (103) is input based on the input current (i _in ) detected by the input current detection unit (22) and the power supply phase (θ _in ) detected by the power supply phase detection unit (21). The current command value (i ₁₀₃ ^* ) is calculated. In this example, the input current command calculation unit (103) includes an input current command generation unit (111), an absolute value calculation unit (112), a subtraction unit (113), and an amplification unit (114). .

The input current command generator (111) performs a Fourier transform on the input current (i _in ) to extract the fundamental frequency component, and calculates a sine value (sin (θ _in )) based on the power supply phase (θ _in ). The input frequency command value (i _in ^* ) is generated by multiplying the fundamental frequency component by the sine value (sin (θ _in )). The absolute value calculator (112) calculates the absolute value (| i _in |) of the input current (i _in ). The subtraction unit (113) subtracts the absolute value (| i _in |) of the input current (i _in ) from the input current command value (i _in ^* ). The amplifying unit (114) multiplies the input current command value (i _in ^* ) subjected to the subtraction processing by the subtracting unit (113) by a predetermined gain, and uses the input current command value subjected to the multiplication processing as the input current command. Output as a value (i ₁₀₃ ^* ).

<Current command generator>
Based on the power supply phase (θ _in ) detected by the power supply phase detection unit (21), the current command generation unit (104) is configured so that the output power waveform in the motor (32) approaches a sine waveform. average torque command value from (102) to (T _ave ^*) modulates generates modulated torque command value (T ^*), is calculated by modulating the torque command value (T ^*) and the input current calculation unit (103) Based on the input current command value (i ₁₀₃ ^* ), the d-axis current command value (i _d ^* ) and the q-axis current command value (i _q ^* ) are generated. In this example, the current command generation unit (104) includes a torque command modulation unit (115), a secondary harmonic application unit (116), an addition unit (117), and a command conversion unit (118). Yes.

The torque command modulation unit (115) calculates a sine value (sin (θ _in )) based on the power supply phase (θ _in ), and based on the sine value (sin (θ _in )), the modulation coefficient (cycle of the power supply voltage) Is determined by multiplying the average torque command value (T _ave ^* ) by the modulation coefficient to generate a modulated torque command value (T ₁₁₅ ^* ). For example, the modulation coefficient is an absolute value (| sin (θ _in ) |) or a square value (sin ² (θ _in )) of a sine value (sin (θ _in )). The secondary harmonic application unit (116) generates a secondary harmonic (a frequency component twice the frequency of the power supply voltage) based on the power supply phase (θ _in ), and generates a modulation torque command value (T ₁₁₅ ^* ). A secondary harmonic is applied to generate a modulated torque command value (T ^* ). As shown in FIG. 3, the modulation torque command value (T ^* ) pulsates with a cycle that is half the cycle (P0) of the power supply voltage.

The adder (117) adds the input current command value (i ₁₀₃ ^* ) to the modulation torque command value (T ^* ). The command conversion unit (118) generates a d-axis current command value (i _d ^* ) and a q-axis current command value (i _q ^* ) based on the command value obtained by the addition process of the addition unit (117). .

The torque command modulation unit (115) includes a power supply phase (theta _in) a predetermined amount (delta) staggered sine value (sin (θ _in + Δ)) to calculate the sine value (sin (θ _in + Δ) ) To determine the modulation coefficient. Alternatively, the torque command modulation unit (115) may change the modulation coefficient according to the power supply frequency (for example, 50 Hz or 60 Hz). In such a configuration, since the frequency component twice the frequency of the power supply voltage is applied to the modulation torque command value (T ₁₁₅ ^* ), the secondary harmonic application unit (116) can be omitted. good.

《Coordinate transformation unit and subtraction unit》
The coordinate conversion unit (105) detects the motor current (u-phase current (i _u ), v-phase current (i _v ), w-phase current (i _w )) and motor phase detected by the motor current detection unit (23). Based on the motor phase (θ _m ) detected by the unit (25), a d-axis current (i _d ) and a q-axis current (i _q ) are calculated. The subtraction unit (106) is obtained by the coordinate conversion unit (105) from the d-axis current command value (i _d ^* ) and the q-axis current command value (i _q ^* ) obtained by the current command generation unit (104). The d-axis current (i _d ) and the q-axis current (i _q ) are subtracted.

<Current control unit>
The current control unit (107) generates a d-axis voltage command value based on the d-axis current command value (i _d ^* ) and the q-axis current command value (i _q ^* ) subjected to the subtraction process by the subtraction unit (106). (V _d ^* ) and q-axis voltage command value (V _q ^* ) are respectively generated.

<Phase adjuster>
The phase adjustment unit (108) is configured to output a d-axis voltage command obtained by the current control unit (107) so that a difference between the current phase (β) and the voltage phase (δ) of the motor (32) is equal to or less than a phase threshold value. Adjust the value (V _d ^* ) and the q-axis voltage command value (V _q ^* ). The current phase (β) of the motor (32) can be calculated based on the d-axis current (i _d ) and the q-axis current (i _q ) obtained by the coordinate conversion unit (105). The voltage phase (δ) of 32) can be calculated based on the d-axis voltage command value (V _d ^* ) and the q-axis voltage command value (V _q ^* ) from the current control unit (107). The phase adjustment processing by the phase adjustment unit (108) will be described in detail later.

<< PWM operation unit >>
The PWM calculation unit (109) switches the inverter circuit (13) based on the d-axis voltage command value (V _d ^* ) and the q-axis voltage command value (V _q ^* ) adjusted by the phase adjustment unit (108). A gate signal (G) for controlling each of the elements (Su, Sv, Sw, Sx, Sy, Sz) is generated. Specifically, the PWM calculation unit (109) controls the duty ratio of the gate signal (G) supplied to each of the switching elements (Su, Sv, Sw, Sx, Sy, Sz). Thus, the switching elements (Su, Sv, Sw, Sx, Sy, Sz) of the inverter circuit (13) perform a switching operation (on / off operation) with the duty ratio set by the PWM calculation unit (109). Thus, by controlling the gate signal (G) based on the d-axis voltage command value (V _d ^* ) and the q-axis voltage command value (V _q ^* ) from the phase adjustment unit (108), the motor (32 ) Is combined with the pulsating component corresponding to the frequency of the power supply voltage and the difference between the current phase (β) and the voltage phase (δ) of the motor (32) is smaller than the phase threshold value. The switching operation of the circuit (13) can be controlled.

<D-axis voltage and q-axis voltage>
Here, the d-axis voltage (V _d ) and the q-axis voltage (V _q ) of the motor (32) will be described. The d-axis voltage (V _d ) and the q-axis voltage (V _q ) of the motor (32) can be expressed as the following equations 1 and 2, respectively.

なお、数式中の記号は、次の通りである。

The symbols in the formula are as follows.

R: Winding resistance p: Differential operator (d / dt)
ω: Actual rotation speed of motor (32) (ω)
φ _a : Induced voltage coefficient (linkage magnetic flux by permanent magnet of rotor of motor (32))
L _d : d-axis inductance L _q : q-axis inductance
i _d : d-axis current (i _d ) i _q : q-axis current (i _q )
V _d ^* : d-axis voltage command value (V _d ^* )
<Current vector and voltage vector>
Next, the current vector (I) and voltage vector (V) of the motor (32) will be described with reference to FIG. The current vector (I) is a vector based on the d-axis current (i _d ) and the q-axis current (i _q ), and the voltage vector (V) is the d-axis voltage (V _d ) and the q-axis voltage (V _q ). Is a vector based on. The voltage vector (V ^* ) is a vector based on the d-axis voltage command value (Vd ^* ) and the q-axis voltage command value (Vq ^* ). That is, the voltage vector (V ^* ) is the voltage vector (V) when the switching operation of the inverter circuit (13) is controlled based on the d-axis voltage command value (Vd ^* ) and the q-axis voltage command value (Vq ^* ). It corresponds to (virtual voltage vector (V)).

When the phase difference between the current vector (I) and the voltage vector (V) of the motor (32) exceeds 90 ° (for example, when the voltage vector (V) becomes the position of the voltage vector (V ^* ) in FIG. 4). ), Energy is regenerated from the motor (32) to the DC link section (12).

<Instantaneous regenerative energy>
In the power converter (10) according to this embodiment, the motor (32) is based on the modulation torque command value (T ^* ) so that the output torque of the motor (32) includes a pulsation component corresponding to the frequency of the power supply voltage. Therefore, the q-axis current (i _q ) and the q-axis voltage (V _q ) of the motor (32) also vary according to the frequency of the power supply voltage. For example, referring to FIG. 3, in the period (P1) in which the modulation torque command value (T ^* ) increases, the time change rate of the q-axis current (i _q ) becomes “positive”, and the above [Equation 2] The electromotive voltage (pL _q i _q ) of the q-axis inductance (L _q ) shown in the second term of the voltage equation is also “positive”. On the other hand, during the period (P2) in which the modulated torque command value (T ^* ) decreases, the time change rate of the q-axis current (i _q ) becomes “negative” and the electromotive voltage (pL _q i) of the q-axis inductance (L _q ) _q ) is also negative.

In addition, during the period (P2) in which the modulation torque command value (T ^* ) decreases, the q-axis voltage (V _q ) increases when the time change rate (that is, the time decrease rate) of the q-axis current (i _q ) increases instantaneously. ) Instantaneously exceeds the reference line (100) (the reference line orthogonal to the current vector (I)) and extends to the opposite side of the current vector (I). As a result, the current vector (I) of the motor (32) There is a possibility that the phase difference from the voltage vector (V) (that is, the difference between the current phase (β) of the motor (32) and the voltage phase (δ)) instantaneously exceeds 90 °. The magnitude of the vector of the electromotive voltage (pL _q i _q ) of the q-axis inductance (L _q ) when the difference between the current phase (β) and the voltage phase (δ) exceeds 90 ° is It can be expressed as Each term in the following equation indicates the magnitude of the vector.

モータ（32）の電流位相（β）と電圧位相（δ）との差が瞬時的に９０°を超えると、モータ（32）から直流リンク部（12）へエネルギーが瞬時的に回生されることになる。なお、電力変換装置（10）では、直流リンク部（12）のコンデンサ（C12）が小容量化されているので、モータ（32）から直流リンク部（12）へ瞬時的に回生されるエネルギー（以下、瞬時回生エネルギーと表記）を十分に吸収することが困難である。

When the difference between the current phase (β) and voltage phase (δ) of the motor (32) instantaneously exceeds 90 °, energy is instantaneously regenerated from the motor (32) to the DC link (12). become. In the power converter (10), since the capacitor (C12) of the DC link unit (12) has a small capacity, the energy instantaneously regenerated from the motor (32) to the DC link unit (12) ( Hereinafter, it is difficult to sufficiently absorb the instantaneous regenerative energy.

<Phase control>
Next, the phase adjustment processing by the phase adjustment unit (108) will be described with reference to FIG. First, the phase adjustment unit (108) calculates the current phase (β) of the motor (32) based on the d-axis current (i _d ) and the q-axis current (i _q ) obtained by the coordinate conversion unit (105). The voltage phase (δ) of the motor (32) is calculated based on the d-axis voltage command value (V _d ^* ) and the q-axis voltage command value (V _q ^* ) from the current control unit (107). Next, the phase adjustment unit (108) determines whether or not the difference between the current phase (β) and the voltage phase (δ) of the motor (32) is equal to or smaller than the phase threshold (90 ° in this example). .

As shown in FIG. 5, when the difference between the current phase (β) and the voltage phase (δ) of the motor (32) is larger than the phase threshold, the phase adjustment unit (108) The q-axis voltage command value (V _q ^* ) from the current control unit (107) is adjusted so that the difference from δ) becomes a predetermined phase setting value (90 ° in this example). Next, the phase adjustment unit (108) converts the d-axis voltage command value (V _d ^* ) from the current control unit (107) and the adjusted q-axis voltage command value (V _q ^* ) into the PWM calculation unit (109 ). Note that the phase setting value is set to a value equal to or smaller than the phase threshold value.

On the other hand, when the difference between the current phase (β) and the voltage phase (δ) of the motor (32) is equal to or smaller than the phase threshold value, the phase adjustment unit (108) receives the d-axis voltage command value from the current control unit (107). (V _d ^* ) and the q-axis voltage command value (V _q ^* ) are output to the PWM calculation unit (109) without adjustment.

In this way, by adjusting the d-axis voltage command value (V _d ^* ) and the q-axis voltage command value (V _q ^* ) by the phase adjustment unit (108), the current phase (β) of the motor (32) and the motor The voltage phase (δ) of the voltage to be applied to the motor (32) can be limited so that the difference from the voltage phase (δ) of the voltage to be applied to (32) is equal to or less than the phase threshold. Thereby, the difference between the current phase (β) and the voltage phase (δ) of the motor (32) can be made equal to or less than the phase threshold value.

<effect>
As described above, by controlling the switching operation of the inverter circuit (13) so that the difference between the current phase (β) and the voltage phase (δ) of the motor (32) is equal to or less than the phase threshold, the motor (32 ) To the DC link (12) can be prevented from instantaneous regeneration. Thereby, the overvoltage breakdown of the inverter circuit (13) due to instantaneous regenerative energy can be prevented.

  In particular, by setting the phase threshold to a value of 90 ° or less, instantaneous regeneration of energy from the motor (32) to the DC link unit (12) can be prevented. Thereby, since it is possible to prevent the DC link voltage of the DC link unit (12) from rising due to the instantaneous regenerative energy, it is possible to reliably prevent the overvoltage breakdown of the inverter circuit (13) due to the instantaneous regenerative energy.

  The instantaneous regenerative energy tends to increase as the difference between the current phase (β) and the voltage phase (δ) of the motor (32) exceeds 90 °. Even if the DC link voltage increases due to instantaneous regenerative energy, if the withstand voltage of the power converter (10) (especially the elements constituting the inverter circuit (13)) is higher than the increased DC link voltage, the inverter circuit The element constituting (13) will not be destroyed. Therefore, the phase threshold is an element (in this example, switching element (Su, Sv, Sw, Sx, Sy, Sz) in which the DC link voltage of the DC link unit (12) forms an inverter circuit (13) by instantaneous regenerative energy And may be set based on the breakdown voltage of the elements constituting the inverter circuit (13) so as not to exceed the breakdown voltage of the freewheeling diodes (Du, Dv, Dw, Dx, Dy, Dz). That is, even if the DC threshold voltage increases due to instantaneous regenerative energy, the phase threshold value is such that the increased DC link voltage is lower than the withstand voltage of the elements constituting the inverter circuit (13). It may be set based on the breakdown voltage of the elements constituting 13). By setting in this way, even if the DC link voltage increases due to instantaneous regenerative energy, the increased DC link voltage can be made lower than the withstand voltage of the elements constituting the inverter circuit (13). And, overvoltage breakdown of the inverter circuit (13) due to instantaneous regenerative energy can be surely prevented.

[Modification 1 of phase adjustment processing]
As shown in FIG. 6, when the difference between the current phase (β) and the voltage phase (δ) of the motor (32) is larger than the phase threshold value (90 ° in this example), the phase adjustment unit (108) The current is set so that the difference between the current phase (β) and the voltage phase (δ) becomes a predetermined phase setting value (90 ° in this example) without changing the magnitude of the voltage vector (V ^* ). The q-axis voltage command value (V _d ^* ) and the q-axis voltage command value (V _q ^* ) from the control unit (107) may be adjusted.

[Modification 2 of phase adjustment processing]
In addition, the current command generation unit (104) determines that the difference between the current phase (β) of the motor (32) and the voltage phase (δ) is equal to or less than the phase threshold value ( _id ^* ) and q A shaft current command value (i _q ^* ) may be generated. For example, as the pulsation width of the modulated torque command value (T ^* ) (that is, the pulsation width of the output torque of the motor (32)) increases, the time change rate of the q-axis current (i _q ) increases. In consideration of this, as shown in FIG. 7, the current command generator (104) causes the q-axis inductance so that the difference between the current phase (β) and the voltage phase (δ) of the motor (32) exceeds the phase threshold. The pulsation width of the modulation torque command value (T ^* ) may be adjusted so that the vector of the electromotive voltage (pL _q i _q ) of (L _q ) does not increase. Even with this configuration, it is possible to suppress the instantaneous regeneration of energy from the motor (32) to the DC link (12), so the overvoltage of the inverter circuit (13) due to the instantaneous regeneration energy Destruction can be prevented. In addition, since the q-axis voltage command value (V _d ^* ) and the q-axis voltage command value (V _q ^* ) are not directly limited, it is possible to suppress deterioration of the current control performance due to the phase adjustment process. In this case, the phase adjustment unit (108) may be omitted.

[Modification 3 of phase adjustment processing]
As shown in FIG. 8, the power conversion device (10) may further include a DC link voltage detection unit (26) that detects the DC link voltage (V _dc ) of the DC link unit (12). In this case, the control unit (14) (more specifically, the phase adjustment unit (108)) causes the DC link voltage (V _dc ) not to exceed the breakdown voltage of the elements constituting the inverter circuit (13) due to instantaneous regenerative energy. as such, the detection value of the breakdown voltage and the DC link voltage of the elements constituting the inverter circuit (13) (V _dc) and (voltage value detected by the DC link voltage detection unit (26) a DC link voltage (V _dc)) The phase threshold value may be adjusted according to the difference. For example, the phase adjustment unit (108) is configured so that the phase threshold value increases as the value obtained by subtracting the detected value of the DC link voltage (V _dc ) from the breakdown voltage of the elements constituting the inverter circuit (13) increases. The phase threshold may be adjusted. In the phase adjustment unit (108), it is preferable that information indicating the breakdown voltage of the elements constituting the inverter circuit (13) is set in advance. Even in such a configuration, it is possible to reliably prevent overvoltage breakdown of the inverter circuit (13) due to instantaneous regenerative energy. In addition, since the phase threshold can be set appropriately according to the difference between the withstand voltage of the elements that make up the inverter circuit (13) and the DC link voltage (V _dc ), the degradation of current control performance due to phase adjustment processing is suppressed. can do.

When the difference between the withstand voltage of the elements constituting the inverter circuit (13) and the detected value of the DC link voltage (V _dc ) is sufficiently large (for example, from the withstand voltage of the elements constituting the inverter (13), the DC link voltage ( The value obtained by subtracting the detected value of V _dc ) is the DC link voltage (DC link voltage due to instantaneous regenerative energy when the difference between the current phase (β) and the voltage phase (δ) of the motor (32) is 180 °. In the case where it is larger than the increase amount of V _dc ), the phase adjustment unit (108) may set the phase threshold to 180 °. When the phase threshold is set to 180 °, the phase adjustment unit (108) does not limit the voltage phase (δ) of the voltage to be applied to the motor (32). That is, during the period when the difference between the withstand voltage of the elements constituting the inverter circuit (13) and the detected value of the DC link voltage (V _dc ) is sufficiently large, the voltage phase (δ) is limited by the phase adjustment unit (108). It will be released.

[Modification 4 of phase adjustment processing]
Further, the magnitude of the voltage applied to the motor (32) (the length of the voltage vector (V) in FIG. 4) and the magnitude of the current supplied to the motor (32) (the current vector (I) in FIG. 4) As the product of (length) increases, the instantaneous regenerative energy tends to increase. By utilizing this, the control unit (14) (more specifically, the phase adjustment unit (108)) uses the instantaneous regenerative energy to make the DC link voltage (V _dc ) of the elements that constitute the inverter circuit (13). The phase threshold may be adjusted according to the product of the magnitude of the voltage applied to the motor (32) and the magnitude of the current supplied to the motor (32) so as not to exceed the breakdown voltage. For example, the phase adjustment unit (108) sets the phase threshold so that the phase threshold increases as the product of the voltage applied to the motor (32) and the current supplied to the motor (32) decreases. You may adjust it. Even in such a configuration, it is possible to reliably prevent overvoltage breakdown of the inverter circuit (13) due to instantaneous regenerative energy.

[Other Embodiments]
The control unit (14) may control the switching operation of the inverter circuit (13) so that the pulsation component corresponding to the frequency of the power supply voltage is not combined with the output torque of the motor (32). Even in the case of such control, the control unit (14) is configured so that the difference between the current phase (β) and the voltage phase (δ) of the motor (32) is smaller than a predetermined phase threshold value. By controlling the switching operation of the inverter circuit (13), it is possible to prevent overvoltage breakdown of the inverter circuit (13) due to instantaneous regenerative energy.

  Further, the case where a single-phase AC power source is used as the AC power source (31) has been described as an example, but a three-phase AC power source can also be used as the AC power source (31).

  The above embodiments are essentially preferable examples, and are not intended to limit the scope of the present invention, its application, or its use.

  As described above, the power conversion device described above is useful for a motor that drives a compressor provided in a refrigerant circuit of an air conditioner.

DESCRIPTION OF SYMBOLS 10 Power converter 11 Converter circuit 12 DC link part 13 Inverter circuit 14 Control part 21 Power supply phase detection part 22 Input current detection part 23 Motor current detection part 24 Motor rotational speed detection part 25 Motor phase detection part 26 DC link voltage detection part 101 Subtraction unit 102 Speed control unit 103 Input current command calculation unit 104 Current command generation unit 105 Coordinate conversion unit 106 Subtraction unit 107 Current control unit 108 Phase adjustment unit 109 PWM calculation unit

Claims (6)

A converter circuit (11) for rectifying the input AC voltage;
A DC link unit (12) that receives the output of the converter circuit (11) and generates a DC voltage including a pulsating component according to the frequency of the input AC voltage;
An inverter circuit (13) that converts a DC voltage from the DC link unit (12) into an output AC voltage and supplies the AC voltage to the motor (32) by switching operation;
A control unit (14) for controlling the switching operation of the inverter circuit (13) so that the difference between the current phase (β) and the voltage phase (δ) of the motor (32) is equal to or less than a predetermined phase threshold value. It equipped with a door,
The control unit (14) causes the DC voltage (V _dc ) of the DC link unit (12) to be generated from the inverter circuit (13) by the energy instantaneously regenerated from the motor (32) to the DC link unit (12). The phase threshold is set according to the difference between the withstand voltage of the elements constituting the inverter circuit (13) and the DC voltage (V _dc ) of the DC link section (12). A power converter configured to adjust . In claim 1,
The controller (14) includes a pulsation component corresponding to the frequency of the input AC voltage in the output torque of the motor (32), and the current phase (β) and voltage phase (δ) of the motor (32). The power conversion device is configured to control the switching operation of the inverter circuit (13) so that the difference between the inverter circuit (13) is equal to or less than the phase threshold value. In claim 1 or 2,
The control unit (14) is configured so that a difference between a current phase (β) of the motor (32) and a voltage phase (δ) of a voltage to be applied to the motor (32) is equal to or less than the phase threshold value. A power conversion device configured to limit a voltage phase (δ) of a voltage to be applied to the motor (32). In any one of Claims 1-3,
The power conversion device, wherein the phase threshold is set to a value of 90 ° or less. In claim 1 or 2,
The control unit (14)
A current command generator (104) that generates a current command value (i _d ^* , i _q ^* ) such that the difference between the current phase (β) and the voltage phase (δ) of the motor (32) is less than or equal to the phase threshold. When,
A current control unit (107) that generates a voltage command value (V _d ^* , V _q ^* ) based on the current command value (i _d ^* , i _q ^* ) generated by the current command generation unit (104);
A PWM calculation unit (109) for controlling the switching operation of the inverter circuit (13) based on the voltage command values (V _d ^* , V _q ^* ) generated by the current control unit (107). The power converter characterized by this.   In any one of Claims 1-5,
  The control unit (14) determines the DC voltage (V) of the DC link unit (12) from the withstand voltage of the elements constituting the inverter circuit (13). _dc ) Is adjusted so that the phase threshold value increases as the value obtained by subtracting
The power converter characterized by the above-mentioned.

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