FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
[See section 10, Rule 13]
POWER CONVERTING APPARATUS, MOTOR DRIVE APPARATUS, AND
REFRIGERATION-CYCLE APPLICATION DEVICE
MITSUBISHI ELECTRIC CORPORATION, A CORPORATION ORGANISED
AND EXISTING UNDER THE LAWS OF JAPAN, WHOSE ADDRESS IS 7-3,
MARUNOUCHI 2-CHOME, CHIYODA-KU, TOKYO 1008310, JAPAN
THE FOLLOWING SPECIFICATION PARTICULARLY DESCRIBES THE
INVENTION AND THE MANNER IN WHICH IT IS TO BE PERFORMED.
2
DESCRIPTION
Field
[0001] The present disclosure relates to a power
converting apparatus that converts alternating-current
power into desired power, a motor drive apparatus, and a5
refrigeration-cycle application device.
Background
[0002] Conventionally, an apparatus such as a motor
drive apparatus that controls an operation of a motor10
controls an operation of converter, an inverter, and the
like according to a state of power input to the converter,
a state of power output from the converter and input to the
inverter, a state of power output from the inverter and
input to the motor, and the like. Such a technique is15
disclosed in Patent Literature 1.
Citation List
Patent Literature
[0003] Patent Literature 1: Japanese Patent Application20
Laid-open No. 2018-7564
Summary of Invention
Problem to be solved by the Invention
[0004] In a case where there is a smoothing capacitor25
between a converter and an inverter, a direct-current bus
voltage that is a voltage across the capacitor is detected
as a parameter of the above-described power states, and is
utilized for controlling the converter, the inverter, and
the like. The direct-current bus voltage, utilized for30
control, is detected at a timing synchronized with a peak
or a valley of a carrier used in the control of the
inverter, at a timing when a control cycle is synchronized
3
with a power supply cycle of a commercial power supply
connected to the converter, or the like, so that an average
value thereof can be roughly acquired. However, in a case
where a detection timing is shifted due to an error in the
control cycle, an error in the power supply cycle, or the5
like, due to the oscillator, the average value of the
direct-current bus voltage cannot be acquired, and a low-
frequency pulsation is superimposed on the detection value
of the direct-current bus voltage. In this case, the
inverter and the like are controlled by using the detection10
value of the direct-current bus voltage on which the low-
frequency pulsation is superimposed, so that there is a
problem that the accuracy of the control is reduced.
[0005] The present disclosure has been made in view of
the above, and an object of the present disclosure is to15
obtain a power converting apparatus capable of improving
the accuracy of the control using a direct-current bus
voltage.
Means to Solve the Problem20
[0006] In order to solve the above-described problems
and achieve the object, a power converting apparatus
according to the present disclosure includes: a rectifier
unit rectifying first alternating-current power supplied
from a commercial power supply; a capacitor connected to an25
output end of the rectifier unit; an inverter connected
across the capacitor, the inverter generating second
alternating-current power and outputting the second
alternating-current power to a motor; a detecting unit
detecting a first direct-current bus voltage, the first30
direct-current bus voltage being a voltage across the
capacitor; and a control unit including a specific
frequency bandpass unit passing a defined frequency band
4
among power-supply pulsatile components contained in the
first direct-current bus voltage, the control unit
controlling an operation of the inverter and the motor by
using a second direct-current bus voltage, the second
direct-current bus voltage being the first direct-current5
bus voltage after passing through the specific frequency
bandpass unit.
Effects of the Invention
[0007] The power converting apparatus according to the10
present disclosure can achieve an effect in which the
accuracy of the control using the direct-current bus
voltage can be improved.
Brief Description of Drawings15
[0008] FIG. 1 is a diagram illustrating a configuration
example of a power converting apparatus according to a
first embodiment.
FIG. 2 is a flowchart illustrating an operation of a
control unit included in the power converting apparatus20
according to the first embodiment.
FIG. 3 is a diagram illustrating an example of a
hardware configuration that implements the control unit
included in the power converting apparatus according to the
first embodiment.25
FIG. 4 is a block diagram illustrating a configuration
example of a control unit included in a power converting
apparatus according to a second embodiment.
FIG. 5 is a block diagram illustrating a configuration
example of a q-axis current pulsation computing unit30
included in the control unit of the power converting
apparatus according to the second embodiment.
FIG. 6 is a diagram illustrating an example of
5
operation waveforms in a case where the q-axis current
pulsation computing unit included in the control unit of
the power converting apparatus according to the second
embodiment is regarded as a pulsation detection unit.
FIG. 7 is a diagram illustrating a configuration5
example of a power converting apparatus according to a
third embodiment.
FIG. 8 is a diagram illustrating a configuration
example of a power converting apparatus according to a
fourth embodiment.10
FIG. 9 is a diagram, as a comparative example,
illustrating an example of operation waveforms in a case
where a second-order low-pass filter is not used as a
specific frequency bandpass unit in the power converting
apparatus.15
FIG. 10 is a diagram illustrating an example of
operation waveforms in a case where the second-order low-
pass filter is used as the specific frequency bandpass unit
in the power converting apparatus according to the fourth
embodiment.20
FIG. 11 is a diagram illustrating a configuration
example of a power converting apparatus according to a
fifth embodiment.
FIG. 12 is a block diagram illustrating a
configuration example of a specific frequency bandpass unit25
included in a control unit of a power converting apparatus
according to a sixth embodiment.
FIG. 13 is a diagram illustrating a configuration
example of a refrigeration-cycle application device
according to a seventh embodiment.30
Description of Embodiments
[0009] Hereinafter, a power converting apparatus, a
6
motor drive apparatus, and a refrigeration-cycle
application device according to embodiments of the present
disclosure will be described in detail with reference to
the drawings.
[0010] First Embodiment.5
FIG. 1 is a diagram illustrating a configuration
example of a power converting apparatus 1 according to a
first embodiment. The power converting apparatus 1 is
connected to a commercial power supply 110 and a compressor
315. The power converting apparatus 1 converts first10
alternating-current power of a power supply voltage Vs,
supplied from the commercial power supply 110 that is a
single-phase commercial power supply, into second
alternating-current power with desired amplitude and phase,
and supplies the second alternating-current power to the15
compressor 315. The power converting apparatus 1 includes
a reactor 120, a rectifier unit 130, a voltage detecting
unit 501, a smoothing unit 200, an inverter 310, current
detecting units 313a and 313b, and a control unit 400.
Note that the power converting apparatus 1 and a motor 31420
included in the compressor 315 constitute a motor drive
apparatus 2.
[0011] The reactor 120 is connected between the
commercial power supply 110 and the rectifier unit 130.
The rectifier unit 130 includes a bridge circuit including25
rectifier elements 131 to 134, and rectifies and outputs
the first alternating-current power of the power supply
voltage Vs supplied from the commercial power supply 110.
The rectifier unit 130 performs full-wave rectification.
The voltage detecting unit 501 detects a direct-current bus30
voltage Vdc that is a voltage of the smoothing unit 200,
that is, a voltage across a capacitor 210. The smoothing
unit 200 is charged by a current, which is rectified by the
7
rectifier unit 130 and flows from the rectifier unit 130
into the smoothing unit 200. The voltage detecting unit
501 outputs the detected voltage value to the control unit
400. The voltage detecting unit 501 is a detecting unit
that detects a power state of the capacitor 210.5
[0012] The smoothing unit 200 is connected to an output
end of the rectifier unit 130. The smoothing unit 200
includes the capacitor 210 as a smoothing element, and
smooths the power rectified by the rectifier unit 130. The
capacitor 210 is, for example, an electrolytic capacitor, a10
film capacitor, or the like. The capacitor 210 is
connected to the output end of the rectifier unit 130, and
has a capacitance to smooth the power rectified by the
rectifier unit 130. A voltage generated in the capacitor
210 by the smoothing is not in a full-wave rectified15
waveform shape of the commercial power supply 110, but in a
waveform shape in which a voltage ripple, corresponding to
the frequency of the commercial power supply 110, is
superimposed on a direct-current component. Therefore, the
voltage does not greatly pulsate. In a case where the20
commercial power supply 110 is a single-phase commercial
power supply, the frequency of the voltage ripple has a
primary component that is twice the frequency of the power
supply voltage Vs. In a case where the power input from
the commercial power supply 110 and the power output from25
the inverter 310 do not change, the amplitude of the
voltage ripple is determined by the capacitance of the
capacitor 210. For example, the voltage ripple generated
in the capacitor 210 pulsates in a range in which the
maximum value of the voltage ripple is less than twice the30
minimum value of the voltage ripple.
[0013] The inverter 310 is connected to the smoothing
unit 200, that is, connected across the capacitor 210. The
8
inverter 310 includes switching elements 311a to 311f and
freewheeling diodes 312a to 312f. The inverter 310 turns
on or off the switching elements 311a to 311f under the
control of the control unit 400 and converts the power
output from the rectifier unit 130 and the smoothing unit5
200 into the second alternating-current power with desired
amplitude and phase. That is, the inverter 310 generates
the second alternating-current power and outputs the second
alternating-current power to the motor 314 of the
compressor 315. The current detecting units 313a and 313b10
each detect a current value of one-phase from among three-
phase currents output from the inverter 310, and outputs
the detected current value to the control unit 400. Note
that, by acquiring current values of two phases from among
the current values of three phases, which are output from15
the inverter 310, the control unit 400 can compute a
current value of the remaining one phase, which is output
from the inverter 310. The compressor 315 is a load and
includes the motor 314 for driving the compressor. The
motor 314 rotates according to the amplitude and the phase20
of the second alternating-current power supplied from the
inverter 310 and performs a compression operation. For
example, in a case where the compressor 315 is a hermetic
compressor used in an air conditioner or the like, the load
torque of the compressor 315 can be regarded as a constant25
torque load in many cases. FIG. 1 illustrates a case where
a motor winding of the motor 314 is a Y connection, but
this is an example, and the present disclosure is not
limited thereto. The motor winding of the motor 314 may be
a Δ connection, or may have a specification capable of30
switching between the Y connection and the Δ connection.
[0014] Note that, in the power converting apparatus 1,
the arrangement of the components illustrated in FIG. 1 is
9
an example, and the arrangement of the components is not
limited to the example illustrated in FIG. 1. For example,
the reactor 120 may be disposed downstream of the rectifier
unit 130. Furthermore, the power converting apparatus 1
may include a booster unit, or the rectifier unit 130 may5
have a function of the booster unit. In the following
description, the voltage detecting unit 501 and the current
detecting units 313a and 313b may be collectively referred
to as a detecting unit in some cases. Furthermore, a
voltage value detected by the voltage detecting unit 50110
and current values detected by the current detecting units
313a and 313b may each be referred to as a detection value
in some cases.
[0015] The control unit 400 acquires a voltage value of
the direct-current bus voltage Vdc of the smoothing unit15
200 from the voltage detecting unit 501, and acquires
current values of the second alternating-current power with
desired amplitude and phase from the current detecting
units 313a and 313b. Here, the second alternating-current
power is obtained through conversion by the inverter 310.20
The control unit 400 controls an operation of the inverter
310, specifically, controls turning on or off of the
switching elements 311a to 311f included in the inverter
310, by using the detection values detected by the
respective detecting units. Furthermore, the control unit25
400 controls an operation of the motor 314 by using the
detection values detected by the respective detecting units.
In the present embodiment, the control unit 400 controls
the operation of the inverter 310 so as to output the
second alternating-current power from the inverter 310 to30
the compressor 315, which is a load. Here, the second
alternating-current power includes a pulsation that depends
on the pulsation of the power flowing from the rectifier
10
unit 130 into the capacitor 210 of the smoothing unit 200.
The pulsation that depends on the pulsation of the power
flowing into the capacitor 210 of the smoothing unit 200 is,
for example, a pulsation that varies depending on the
frequency, and the like, of the pulsation of the power5
flowing into the capacitor 210 of the smoothing unit 200.
With such a configuration, the control unit 400 reduces the
current flowing through the capacitor 210 of the smoothing
unit 200. Note that the control unit 400 may not use all
the detection values acquired from the respective detecting10
units, and may perform control by using some detection
values.
[0016] The control unit 400 performs control such that
any of the speed, the voltage, and the current of the motor
314 becomes a desired state. Here, in a case where the15
motor 314 is used for driving the compressor 315 and the
compressor 315 is a hermetic compressor, it is difficult to
mount a position sensor that detects a rotor position to
the motor 314 due to the structural and cost constraints.
Therefore, the control unit 400 controls the motor 31420
without a position sensor. The position sensorless control
method of the motor 314 includes primary magnetic flux
constant control, sensorless vector control, and the like.
In the present embodiment, description will be made based
on the sensorless vector control as an example. Note that25
the control method described below can be applied to the
primary magnetic flux constant control or other methods
with a minor change. In the present embodiment, as will be
described later, the control unit 400 controls the
operation of the inverter 310 and the motor 314 by using dq30
rotational coordinates that rotate in synchronization with
the rotor position of the motor 314.
[0017] In the present embodiment, the control unit 400
11
includes a specific frequency bandpass unit 450 that passes
a defined frequency band among power-supply pulsatile
components contained in the direct-current bus voltage Vdc
detected by the voltage detecting unit 501. The control
unit 400 controls the operation of the inverter 310 and the5
motor 314 by using a direct-current bus voltage Vdc'. The
direct-current bus voltage Vdc' is the direct-current bus
voltage Vdc, detected by the voltage detecting unit 501,
after passing through the specific frequency bandpass unit
450. In the following description, the direct-current bus10
voltage Vdc detected by the voltage detecting unit 501 may
be referred to as a first direct-current bus voltage, and
the direct-current bus voltage Vdc', which is the direct-
current bus voltage Vdc after passing through the specific
frequency bandpass unit 450, may be referred to as a second15
direct-current bus voltage in some cases.
[0018] In a case where the frequency of the power-supply
pulsatile components contained in the direct-current bus
voltage Vdc detected by the voltage detecting unit 501 is n
times that of the commercial power supply 110, that is, in20
a case where the direct-current bus voltage Vdc pulsates
with the frequency n times that of the commercial power
supply 110, in the present embodiment, an m-th order filter
is applied as the specific frequency bandpass unit 450.
Specifically, the frequency n times that of the commercial25
power supply 110 is a frequency n times that of the power
supply voltage Vs supplied from the commercial power supply
110. Note that n and m are integers of two or more. As
the specific frequency bandpass unit 450, a finite impulse
response (FIR) filter or an infinite impulse response (IIR)30
filter may be used instead of the m-th order filter.
[0019] An operation of the control unit 400 will be
described with reference to a flowchart. FIG. 2 is a
12
flowchart illustrating the operation of the control unit
400 included in the power converting apparatus 1 according
to the first embodiment. The control unit 400 acquires the
direct-current bus voltage Vdc, which is a detection value,
of the capacitor 210 from the voltage detecting unit 5015
(step S1). The control unit 400 causes the acquired
direct-current bus voltage Vdc to pass through the specific
frequency bandpass unit 450 (step S2). The control unit
400 controls the inverter 310 and the like by using the
direct-current bus voltage Vdc', which is the direct-10
current bus voltage Vdc after passing through the specific
frequency bandpass unit 450 (step S3).
[0020] Next, a hardware configuration of the control
unit 400 included in the power converting apparatus 1 will
be described. FIG. 3 is a diagram illustrating an example15
of the hardware configuration that implements the control
unit 400 included in the power converting apparatus 1
according to the first embodiment. The control unit 400 is
implemented by a processor 91 and a memory 92.
[0021] The processor 91 may be a central processing unit20
(CPU, also referred to as a central processing device, a
processing device, a computing device, a microprocessor, a
microcomputer, a processor, a digital signal processor
(DSP)), or may be a system large scale integration (LSI).
Examples of the memory 92 can include a nonvolatile or25
volatile semiconductor memory such as a random access
memory (RAM), a read only memory (ROM), a flash memory, an
erasable programmable read only memory (EPROM), and an
electrically erasable programmable read only memory (EEPROM
(registered trademark). Furthermore, the memory 92 is not30
limited thereto, and may be a magnetic disk, an optical
disk, a compact disk, a mini disk, or a digital versatile
disc (DVD).
13
[0022] As described above, according to the present
embodiment, in the power converting apparatus 1, the
control unit 400 is configured to acquire the direct-
current bus voltage Vdc detected by the voltage detecting
unit 501, and to control the inverter 310 and the like by5
using the direct-current bus voltage Vdc', which is the
direct-current bus voltage Vdc having passed through the
specific frequency bandpass unit 450. Therefore, the
control unit 400 can improve the accuracy of the control
using the direct-current bus voltage Vdc.10
[0023] Second Embodiment.
In a second embodiment, a case will be described where
a high-pass filter is used as a specific example of the
specific frequency bandpass unit 450. In the second
embodiment, the commercial power supply 110 connected to15
the power converting apparatus 1 is a single-phase
commercial power supply as illustrated in FIG. 1.
[0024] In the second embodiment, the power converting
apparatus 1 has a configuration similar to that of the
power converting apparatus 1 in the first embodiment20
illustrated in FIG. 1. FIG. 4 is a block diagram
illustrating a configuration example of the control unit
400 included in the power converting apparatus 1 according
to the second embodiment. The control unit 400 includes a
rotor position estimation unit 401, a speed control unit25
402, a magnetic flux weakening control unit 403, a current
control unit 404, coordinate conversion units 405 and 406,
a PWM signal generation unit 407, a q-axis current
pulsation computing unit 408, an addition unit 409, and the
specific frequency bandpass unit 450.30
[0025] The rotor position estimation unit 401 estimates,
from a dq-axis voltage command vector Vdq* and a dq-axis
current vector idq applied to the motor 314, an estimated
14
phase angle θest, which is a direction of a rotor magnetic
pole on a dq axis, and an estimated speed ωest, which is a
rotor speed, with respect to the rotor (not illustrated)
included in the motor 314.
[0026] The speed control unit 402 generates, from a5
speed command ω* and the estimated speed ωest, a q-axis
current command iqDC*. Specifically, the speed control unit
402 automatically adjusts the q-axis current command iqDC*
such that the speed command ω* matches the estimated speed
ωest. In a case where the power converting apparatus 1 is10
used as a refrigeration-cycle application device in an air
conditioner or the like, the speed command ω* is based on,
for example, a temperature detected by a temperature sensor
(not illustrated), information indicating a set temperature
instructed from a remote controller, which is an operation15
unit (not illustrated), operation mode selection
information, operation start and operation end instruction
information, and the like. The operation mode includes,
for example, heating, cooling, dehumidification, and the
like.20
[0027] The magnetic flux weakening control unit 403
automatically adjusts a d-axis current command id* such
that an absolute value of the dq-axis voltage command
vector Vdq* falls within a limiting value of a voltage
limiting value Vlim*. Furthermore, the magnetic flux25
weakening control unit 403 performs magnetic flux weakening
control in consideration of a q-axis current pulsation
command iqrip* computed by the q-axis current pulsation
computing unit 408. The magnetic flux weakening control
falls roughly into two categories: a method of calculating30
the d-axis current command id* from an equation of a
voltage limit ellipse; and a method of calculating the d-
axis current command id* such that the deviation between
15
absolute values of the voltage limiting value Vlim* and the
dq-axis voltage command vector Vdq* becomes zero, and either
method may be used.
[0028] The current control unit 404 controls the current
flowing through the motor 314 by using a q-axis current5
command iq* and the d-axis current command id*, and
generates the dq-axis voltage command vector Vdq*.
Specifically, the current control unit 404 automatically
adjusts the dq-axis voltage command vector Vdq* such that
the dq-axis current vector idq follows the d-axis current10
command id* and the q-axis current command iq*. In the
following description, the dq-axis voltage command vector
Vdq* may simply be referred to as a dq-axis voltage command
in some cases.
[0029] The coordinate conversion unit 405 coordinate-15
converts the dq-axis voltage command vector Vdq* from dq
coordinates to a voltage command Vuvw* of an alternating-
current quantity on the basis of the estimated phase angle
θest.
[0030] The coordinate conversion unit 406 coordinate-20
converts a current Iuvw flowing through the motor 314 from
the alternating-current quantity to the dq-axis current
vector idq of the dq coordinates on the basis of the
estimated phase angle θest. As described above, with
respect to the current Iuvw flowing through the motor 314,25
the control unit 400 can acquire current values of two
phases, which are detected by the current detecting units
313a and 313b, from among the current values of the three
phases, which are output from the inverter 310. In
addition, the control unit 400 can acquire a current value30
of the remaining one phase by using the current values of
the two phases. Furthermore, in the present embodiment, a
method of reproducing the three-phase current by acquiring
16
the current value of the current flowing through the motor
314 is described, but the reproducing may be performed by
another method such as a method of reproducing the three-
phase current by acquiring a current value of a current
flowing between the capacitor 210 of the smoothing unit 2005
and the inverter 310.
[0031] The PWM signal generation unit 407 generates a
PWM signal on the basis of the voltage command Vuvw*
obtained through coordinate-conversion by the coordinate
conversion unit 405. The control unit 400 applies a10
voltage to the motor 314 by outputting the PWM signal
generated by the PWM signal generation unit 407 to the
switching elements 311a to 311f of the inverter 310.
[0032] The q-axis current pulsation computing unit 408
computes a q-axis current pulsation by using the direct-15
current bus voltage Vdc', and generates the above-described
q-axis current pulsation command iqrip*, which is a
pulsatile component of the q-axis current command iq*.
Specifically, the q-axis current pulsation computing unit
408 calculates the q-axis current pulsation command iqrip*
20
on the basis of the direct-current bus voltage Vdc'. The
direct-current bus voltage Vdc' is the direct-current bus
voltage Vdc, detected by the voltage detecting unit 501,
after passing through the specific frequency bandpass unit
450. The pulsation amplitude of the q-axis current iq25
varies depending on the driving condition of the motor 314.
Therefore, the q-axis current pulsation computing unit 408
determines the amplitude by appropriately considering the
driving condition.
[0033] The addition unit 409 adds the q-axis current30
command iqDC* output from the speed control unit 402 and the
q-axis current pulsation command iqrip* computed by the q-
axis current pulsation computing unit 408 to generate the
17
q-axis current command iq*, and outputs the q-axis current
command iq* to the current control unit 404.
[0034] FIG. 5 is a block diagram illustrating a
configuration example of the q-axis current pulsation
computing unit 408 included in the control unit 400 of the5
power converting apparatus 1 according to the second
embodiment. The q-axis current pulsation computing unit
408 includes a subtraction unit 420, Fourier coefficient
computing units 421 to 424, proportional integral
differential (PID) control units 425 to 428, and an10
alternating-current restoration unit 429. Note that the
specific frequency bandpass unit 450 is also illustrated in
FIG. 5.
[0035] The subtraction unit 420 computes a deviation
between a target value, which is zero, and the direct-15
current bus voltage Vdc'.
[0036] The Fourier coefficient computing units 421 to
424 calculate amplitudes of a sin2f component, a cos2f
component, a sin4f component, and a cos4f component,
respectively, included in the deviation computed by the20
subtraction unit 420 with the power supply frequency of the
commercial power supply 110 as a 1f component. The Fourier
coefficient computing units 421 to 424 only have different
target specific frequency components and the calculation
contents are similar to each other.25
[0037] The PID control units 425 to 428 are each
connected to one of the Fourier coefficient computing units
421 to 424. The PID control units 425 to 428 perform
proportional integral derivative control such that the
specific frequency components of the deviation calculated30
by the Fourier coefficient computing units 421 to 424 each
become zero. The PID control units 425 to 428 receive
different values input from the connected Fourier
18
coefficient computing units 421 to 424, but only have
different target specific frequency components, and the
control contents are similar to each other.
[0038] The alternating-current restoration unit 429
restores an alternating-current signal by using the outputs5
from the PID control units 425 to 428, and outputs the
restored alternating-current signal as the q-axis current
pulsation command iqrip*. Here, the direct-current bus
voltage Vdc is obtained by integrating a charge/discharge
current I3 of the capacitor 210 and dividing the value10
obtained through the integration by the capacitance of the
capacitor 210. Therefore, there is a phase difference of
90 degrees between the charge/discharge current I3 of the
capacitor 210 and the direct-current bus voltage Vdc.
Accordingly, the alternating-current restoration unit 42915
needs to determine the q-axis current pulsation command
iqrip* in consideration of the phase difference. In a case
where the phase difference is θoffset(=π/2[rad]) and the
detection signals multiplied by the Fourier coefficient
computing units 421 to 424 are sin2ωint, cos2ωint, sin4ωint,20
and cos4ωint, respectively, the alternating-current
restoration unit 429 sets restoration signals to
sin2(ωint+θoffset), cos2(ωint+θoffset), sin4(ωint+θoffset), and
cos4(ωint+θoffset). The alternating-current restoration unit
429 can determine the q-axis current pulsation command25
iqrip* by calculating the sum of products of the outputs
from the PID control units 425 to 428 and the restoration
signals. Note that, as illustrated in FIG. 1, in the power
converting apparatus 1, an input current from the rectifier
unit 130 to the capacitor 210 of the smoothing unit 200 is30
set as an input current I1, an output current from the
capacitor 210 of the smoothing unit 200 to the inverter 310
is set as an output current I2, and the charge/discharge
19
current of the capacitor 210 of the smoothing unit 200 is
set as the charge/discharge current I3.
[0039] The control unit 400 eliminates a direct-current
component from the direct-current bus voltage Vdc detected
by the voltage detecting unit 501 by using the specific5
frequency bandpass unit 450 that is a high-pass filter, and
performs pulsation detection processing, PID control, and
alternating-current restoration processing in the q-axis
current pulsation computing unit 408. With such a
configuration, the control unit 400 can improve the10
stability of smoothing element current reduction control of
reducing the charge/discharge current I3 of the capacitor
210, and can reduce the pulsation of the direct-current bus
voltage Vdc and the pulsation of the charge/discharge
current I3 of the capacitor 210. This is because an error15
in pulsation detection can be reduced by eliminating the
direct-current component from the direct-current bus
voltage Vdc by the specific frequency bandpass unit 450
that is a high-pass filter.
[0040] The specific frequency bandpass unit 450 that is20
a high-pass filter may include an FIR filter or an IIR
filter. In the control unit 400, as in Equation (1), the
high-pass filter may be equivalently implemented by using a
low-pass filter as the specific frequency bandpass unit 450.
As will be described later, in Equation (1), the second25
term on the right side is an expression representing a low-
pass filter. Note that Equation (1) uses a second-order
low-pass filter, but may use another filter, such as a
first-order low-pass filter, which attenuates a high
frequency range.30
[0041] Formula 1:
20
[0042] In Equation (1), s is a Laplace operator, ζ is an
attenuation coefficient, and ωn is cutoff angular frequency.
The attenuation coefficient ζ is a parameter that affects
the vibrational property of the response. A filter using
√(2) as the attenuation coefficient ζ is called a second-5
order Butterworth filter, and has a characteristic that the
signal becomes -3dB at cutoff angular frequency ωn. Note
that √(2) represents a square root of 2. By using the
second-order low-pass filter, attenuation performance of
the pulsatile component can be improved from -20dB/decade10
to -40dB/decade as compared with the first-order low-pass
filter. Therefore, both the response performance and the
attenuation performance of the pulsatile component can be
achieved.
[0043] In order to simplify the description, here, the15
attenuation coefficient ζ is set to √(2) such that the
second-order low-pass filter becomes the second-order
Butterworth filter, but the point at which the signal
becomes -3dB may be changed by adjusting the cutoff angular
frequency ωn and the attenuation coefficient ζ. The20
pulsatile component can be eliminated from the signal by
appropriately designing the cutoff angular frequency ωn for
the frequency component that is desired to be attenuated.
For example, in order to attenuate a pulsatile component
ω2f having a frequency twice the power supply frequency25
generated in the commercial power supply 110, the cutoff
angular frequency ωn just needs to be designed to be equal
to or lower than the frequency of the pulsatile component
ω2f, having a frequency twice the power supply frequency.
For example, if it is desired to attenuate the pulsatile30
component ω2f having a frequency twice the power supply
frequency by 99% from the detected direct-current bus
voltage Vdc, the cutoff angular frequency ωn just needs to
21
be designed to be 1/10 the frequency of the pulsatile
component ω2f, having a frequency twice the power supply
frequency.
[0044] Here, operation waveforms in a case where the q-
axis current pulsation computing unit 408 included in the5
control unit 400 is regarded as a pulsation detection unit
will be described. FIG. 6 is a diagram illustrating an
example of operation waveforms in a case where the q-axis
current pulsation computing unit 408 included in the
control unit 400 of the power converting apparatus 110
according to the second embodiment is regarded as a
pulsation detection unit. In FIG. 6, an upper diagram
illustrates a detection source signal that is the direct-
current bus voltage Vdc, and a lower diagram illustrates a
detection signal that is the q-axis current pulsation15
command iqrip*. Note that the horizontal axis represents
time in both the upper diagram and the lower diagram. In
the detection signal, a solid line indicates a real value
of the pulsatile component that is a detection target. As
a comparative example, in a case where a high-pass filter20
is not used for the detection source signal, it can be seen
that a direct-current component is superimposed on the
detection signal. The superimposition of the direct-
current component deteriorates an effect of control such as
the smoothing element current reduction control, described25
above. On the other hand, in the present embodiment, it
can be seen that the signal can be detected without the
superimposition of the direct-current component, by
eliminating the direct-current component from the detection
source signal by using a high-pass filter and then30
performing pulsation detection.
[0045] By using a high-pass filter for the detection
value of the direct-current bus voltage Vdc, the control
22
unit 400 can improve the accuracy of the pulsation
detection, and improve the control performance in the
smoothing element current reduction control and the like.
Furthermore, by using a high-pass filter for the detection
value of the direct-current bus voltage Vdc, the control5
unit 400 can prevent an increase in copper loss of the
motor 314 and in conduction loss of the inverter 310 caused
by the superimposition of a low-frequency pulsatile
component on the direct-current bus voltage Vdc and a motor
current. Furthermore, by using a high-pass filter for the10
detection value of the direct-current bus voltage Vdc, the
control unit 400 can improve the control performance also
in, for example, vibration reduction control of reducing
vibrations generated in the motor 314, the compressor 315,
and the like, in addition to the smoothing element current15
reduction control.
[0046] Note that the characteristic of the high-pass
filter in a case where the high-pass filter is used as the
specific frequency bandpass unit 450 can be appropriately
set in a manner of software in the control unit 400. The20
control unit 400 uses a second-order high-pass filter as
the specific frequency bandpass unit 450. For example, in
a case where the commercial power supply 110 is a single-
phase commercial power supply, the control unit 400 sets
the control band of the specific frequency bandpass unit25
450 to be twice or lower than the frequency of the single-
phase commercial power supply, and attenuates a second-
order or lower component of the frequency of the single-
phase commercial power supply at a rate of -40dB/decade or
more. The frequency of the single-phase commercial power30
supply is generally 50 Hz or 60 Hz.
[0047] As described above, according to the present
embodiment, in the power converting apparatus 1 connected
23
to the commercial power supply 110 that is a single-phase
commercial power supply, the control unit 400 can improve
the control performance in the smoothing element current
reduction control, and the like, of reducing the
charge/discharge current I3 of the capacitor 210, by using5
a high-pass filter as the specific frequency bandpass unit
450.
[0048] Third Embodiment.
In the second embodiment, the case where the
commercial power supply 110 is a single-phase commercial10
power supply has been described as an example of using a
high-pass filter as the specific frequency bandpass unit
450. In a third embodiment, a case where the commercial
power supply is a three-phase commercial power supply will
be described as an example of using a high-pass filter as15
the specific frequency bandpass unit 450.
[0049] FIG. 7 is a diagram illustrating a configuration
example of a power converting apparatus 1a according to the
third embodiment. The power converting apparatus 1a is
connected to a commercial power supply 110a and the20
compressor 315. The power converting apparatus 1a converts
the first alternating-current power of the power supply
voltage Vs, supplied from the commercial power supply 110a
that is a three-phase commercial power supply, into the
second alternating-current power with desired amplitude and25
phase, and supplies the second alternating-current power to
the compressor 315. The power converting apparatus 1a
includes reactors 120 to 122, a rectifier unit 130a, the
voltage detecting unit 501, the smoothing unit 200, the
inverter 310, the current detecting units 313a and 313b,30
and the control unit 400. Note that the power converting
apparatus 1a and the motor 314 included in the compressor
315 constitute a motor drive apparatus 2a.
24
[0050] The reactors 120 to 122 are connected between the
commercial power supply 110a and the rectifier unit 130a.
The rectifier unit 130a includes a rectifier circuit
including rectifier elements 131 to 136, and rectifies and
outputs the first alternating-current power of the power5
supply voltage Vs supplied from the commercial power supply
110a. The rectifier unit 130a performs full-wave
rectification. The voltage detecting unit 501 detects the
direct-current bus voltage Vdc that is a voltage of the
smoothing unit 200, that is, a voltage across the capacitor10
210. The smoothing unit 200 is charged by a current, which
is rectified by the rectifier unit 130a and flows from the
rectifier unit 130a to the smoothing unit 200. The voltage
detecting unit 501 outputs the detected voltage value to
the control unit 400. The voltage detecting unit 501 is a15
detecting unit that detects the power state of the
capacitor 210.
[0051] The smoothing unit 200 is connected to an output
end of the rectifier unit 130a. The smoothing unit 200
includes the capacitor 210 as a smoothing element, and20
smooths the power rectified by the rectifier unit 130a.
The capacitor 210 is, for example, an electrolytic
capacitor, a film capacitor, or the like. The capacitor
210 is connected to the output end of the rectifier unit
130a, and has a capacitance to smooth the power rectified25
by the rectifier unit 130a. A voltage generated in the
capacitor 210 by the smoothing is not in a full-wave
rectified waveform shape of the commercial power supply 110,
but in a waveform shape in which a voltage ripple,
corresponding to the frequency of the commercial power30
supply 110a, is superimposed on a direct-current component.
Therefore, the voltage does not greatly pulsate. In a case
where the commercial power supply 110a is a three-phase
25
commercial power supply, the frequency of the voltage
ripple has a primary component that is six times the
frequency of the power supply voltage Vs. In a case where
the power input from the commercial power supply 110a and
the power output from the inverter 310 do not change, the5
amplitude of the voltage ripple is determined by the
capacitance of the capacitor 210. For example, the voltage
ripple generated in the capacitor 210 pulsates in a range
in which the maximum value of the voltage ripple is less
than twice the minimum value of the voltage ripple.10
[0052] The configuration and operation of the control
unit 400 are similar to the configuration and operation of
the control unit 400 in the second embodiment, but the
setting of the specific frequency bandpass unit 450 is
different. As described above, a voltage ripple is15
superimposed on a voltage generated in the capacitor 210 by
the smoothing. In a case where the commercial power supply
110 is a single-phase commercial power supply, the
frequency of the voltage ripple has a primary component
that is twice the frequency of the power supply voltage Vs.20
In a case where the commercial power supply 110a is a
three-phase commercial power supply, the frequency of the
voltage ripple has a primary component that is six times
the frequency of the power supply voltage Vs.
[0053] The specific frequency bandpass unit 450 that is25
a high-pass filter may include an FIR filter or an IIR
filter. In the control unit 400, similarly to the second
embodiment, a high-pass filter may be equivalently
implemented by using a low-pass filter as the specific
frequency bandpass unit 450.30
[0054] In order to simplify the description, similarly
to the second embodiment, the attenuation coefficient ζ is
set to √(2) such that the second-order low-pass filter
26
becomes the second-order Butterworth filter, but the point
at which the signal becomes -3dB may be changed by
adjusting the cutoff angular frequency ωn and the
attenuation coefficient ζ. The pulsatile component can be
eliminated from the signal by appropriately designing the5
cutoff angular frequency ωn for the frequency component
that is desired to be attenuated. For example, in order to
attenuate a pulsatile component ω6f having a frequency six
times the power supply frequency generated in the
commercial power supply 110a, the cutoff angular frequency10
ωn just needs to be designed to be equal to or lower than
the frequency of the pulsatile component ω6f, having a
frequency six times the power supply frequency. For
example, if it is desired to attenuate the pulsatile
component ω6f having a frequency six times the power supply15
frequency by 99% from the detected direct-current bus
voltage Vdc, the cutoff angular frequency ωn just needs to
be designed to be 1/10 the frequency of the pulsatile
component ω6f, having a frequency six times the power
supply frequency.20
[0055] By using a high-pass filter for the detection
value of the direct-current bus voltage Vdc, even when the
connected power supply is the commercial power supply 110a
that is a three-phase commercial power supply, the control
unit 400 can improve the accuracy of the pulsation25
detection, and improve the control performance in the
smoothing element current reduction control and the like,
similarly to the case where the commercial power supply 110
is a single-phase commercial power supply. Furthermore, by
using a high-pass filter for the detection value of the30
direct-current bus voltage Vdc, the control unit 400 can
prevent an increase in copper loss of the motor 314 and in
conduction loss of the inverter 310 caused by the
27
superimposition of a low-frequency pulsatile component on
the direct-current bus voltage Vdc and the motor current.
Furthermore, by using a high-pass filter for the detection
value of the direct-current bus voltage Vdc, the control
unit 400 can improve the control performance also in, for5
example, vibration reduction control of reducing vibrations
generated in the motor 314, the compressor 315, and the
like, in addition to the smoothing element current
reduction control.
[0056] Similarly to the second embodiment, the10
characteristic of the high-pass filter in a case where the
high-pass filter is used as the specific frequency bandpass
unit 450 can be appropriately set in a manner of software
in the control unit 400. The control unit 400 uses a
second-order high-pass filter as the specific frequency15
bandpass unit 450. For example, in a case where the
commercial power supply 110a is a three-phase commercial
power supply, the control unit 400 sets the control band of
the specific frequency bandpass unit 450 to be six times or
lower than the frequency of the three-phase commercial20
power supply, and attenuates sixth-order or lower component
of the frequency of the three-phase commercial power supply
at a rate of -40dB/decade or more. The frequency of the
three-phase commercial power supply is generally 50 Hz or
60 Hz.25
[0057] As described above, according to the present
embodiment, in the power converting apparatus 1a connected
to the commercial power supply 110a that is a three-phase
commercial power supply, the control unit 400 can,
similarly to the second embodiment, improve the control30
performance in the smoothing element current reduction
control, and the like, of reducing the charge/discharge
current I3 of the capacitor 210, by using a high-pass
28
filter as the specific frequency bandpass unit 450.
[0058] Fourth Embodiment.
In a fourth embodiment, a case will be described where
a low-pass filter is used as a specific example of the
specific frequency bandpass unit 450. In the fourth5
embodiment, the commercial power supply 110 connected to
the power converting apparatus is a single-phase commercial
power supply.
[0059] FIG. 8 is a diagram illustrating a configuration
example of a power converting apparatus 1b according to the10
fourth embodiment. The power converting apparatus 1b is
connected to the commercial power supply 110 and the
compressor 315. The power converting apparatus 1b converts
the first alternating-current power of the power supply
voltage Vs, supplied from the commercial power supply 11015
that is a single-phase commercial power supply, into the
second alternating-current power with desired amplitude and
phase, and supplies the second alternating-current power to
the compressor 315. The power converting apparatus 1b
includes the reactor 120, the rectifier unit 130, a booster20
unit 150, the voltage detecting unit 501, the smoothing
unit 200, the inverter 310, the current detecting units
313a and 313b, and a control unit 400b. Note that the
power converting apparatus 1b and the motor 314 included in
the compressor 315 constitute a motor drive apparatus 2b.25
[0060] The booster unit 150 boosts a voltage of direct-
current power output from the rectifier unit 130 under the
control of the control unit 400b. The booster unit 150
includes, for example, a booster circuit using a reactor, a
switching element, a diode, and the like, but is enough to30
have a general configuration and is not particularly
limited.
[0061] Similarly to the control unit 400, the control
29
unit 400b controls the operation of the inverter 310 and
the motor 314, and controls the operation of the booster
unit 150 such that the direct-current bus voltage Vdc
detected by the voltage detecting unit 501 becomes a
desired value. Note that, in the present embodiment, a5
single control unit 400b controls the operation of the
inverter 310, the motor 314, and the booster unit 150, but
the present disclosure is not limited thereto. A control
unit that controls the operation of the inverter 310 and
the motor 314 and a control unit that controls the10
operation of the booster unit 150 may be separately
provided. Note that, in a case where the specific
frequency bandpass unit 450 is provided in each control
unit, the fewer the number of control units, the simpler
the overall configuration of the power converting apparatus15
1b can be.
[0062] In the present embodiment, the control unit 400b
uses a second-order low-pass filter as the specific
frequency bandpass unit 450. The control unit 400b
eliminates a pulsatile component having a frequency 2n20
times the power supply frequency generated in the
commercial power supply 110 from the direct-current bus
voltage Vdc, by using the second-order low-pass filter, and
prevents the superimposition of a low-frequency pulsatile
component on the direct-current bus voltage Vdc'. By using25
the direct-current bus voltage Vdc' from which a high-
frequency component, that is, a pulsatile component has
been eliminated by the second-order low-pass filter, the
control unit 400b can improve the limitation of the
operation region of the magnetic flux weakening control30
caused by the pulsatile component, for example. The
second-order low-pass filter is expressed by Equation (2)
as described above.
30
[0063] Formula 2:
[0064] The attenuation coefficient ζ is a parameter that
affects the vibrational property of the response. A filter
using √(2) as the attenuation coefficient ζ is called a5
second-order Butterworth filter, and has a characteristic
that the signal becomes -3dB at the cutoff angular
frequency ωn. By using the second-order low-pass filter,
the attenuation performance of the pulsatile component can
be improved from -20dB/decade to -40dB/decade as compared10
with the first-order low-pass filter. Therefore, both the
response performance and the attenuation performance of the
pulsatile component can be achieved.
[0065] In order to simplify the description, here, the
attenuation coefficient ζ is set to √(2) such that the15
second-order low-pass filter becomes the second-order
Butterworth filter, but the point at which the signal
becomes -3dB may be changed by adjusting the cutoff angular
frequency ωn and the attenuation coefficient ζ. The
pulsatile component can be eliminated from the signal by20
appropriately designing the cutoff angular frequency ωn for
the frequency component that is desired to be attenuated.
For example, in order to attenuate the pulsatile component
ω2f having a frequency twice the power supply frequency
generated in the commercial power supply 110, the cutoff25
angular frequency ωn just needs to be designed to be equal
to or lower than the frequency of the pulsatile component
ω2f, having a frequency twice the power supply frequency.
For example, if it is desired to attenuate the pulsatile
component ω2f having a frequency twice the power supply30
frequency by 99% from the detected direct-current bus
voltage Vdc, the cutoff angular frequency ωn just needs to
31
be designed to be 1/10 the frequency of the pulsatile
component ω2f, having a frequency twice the power supply
frequency.
[0066] Here, as a comparative example, operation
waveforms in a case where the second-order low-pass filter5
is not used as the specific frequency bandpass unit 450 in
the power converting apparatus will be described as a
comparative example. FIG. 9 is a diagram, as a comparative
example, illustrating an example of operation waveforms in
a case where the second-order low-pass filter is not used10
as the specific frequency bandpass unit in the power
converting apparatus. In FIG. 9, an upper diagram
illustrates the direct-current bus voltage Vdc, and a lower
diagram illustrates the motor current. Note that the
horizontal axis represents time in both the upper diagram15
and the lower diagram. In a case where the second-order
low-pass filter is not used for the direct-current bus
voltage Vdc, an average value of the direct-current bus
voltage Vdc cannot be acquired due to an error in detection
timing, so that the low-frequency pulsatile component may20
be superimposed on the direct-current bus voltage Vdc in
some cases. In such a case, the low-frequency pulsatile
component is superimposed also on the direct-current bus
voltage Vdc by feedback control resulting from the control
of the direct-current bus voltage. Furthermore, the25
direct-current bus voltage Vdc pulsates and thus the motor
current also pulsates. As a result, problems arise such as
an increase in loss and a reduction in drivable range of
the motor.
[0067] FIG. 10 is a diagram illustrating an example of30
operation waveforms in a case where the second-order low-
pass filter is used as the specific frequency bandpass unit
450 in the power converting apparatus 1b according to the
32
fourth embodiment. By attenuating a pulsatile component of
the direct-current bus voltage Vdc by using the second-
order low-pass filter, the control unit 400b can reduce the
superimposition of the low-frequency component having a
frequency twice or lower the power supply frequency caused5
by an error in voltage detection timing. Accordingly, the
control unit 400b can reduce a low-order harmonic of the
motor current. Therefore, the control unit 400b can
acquire an effect of reducing the conduction loss of the
inverter 310 and the copper loss of the motor 314.10
Furthermore, the control unit 400b can acquire a noise
reduction effect by eliminating a beat component. As
described above, by using the direct-current bus voltage
Vdc' from which a high-frequency component, that is, a
pulsatile component has been eliminated by the second-order15
low-pass filter, the control unit 400b can improve the
limitation of the operation region of the magnetic flux
weakening control caused by the pulsatile component, for
example. These effects, such as pulsation eliminating
effects achieved by the second-order low-pass filter, are20
profound particularly in a region such as a low-speed high-
load range where a current becomes large, and under an
operating condition where pulsation of 2n component
generated in a direct-current voltage output from the
rectifier unit 130 without boosting operation is large.25
[0068] Note that the characteristic of the low-pass
filter in a case where the low-pass filter is used as the
specific frequency bandpass unit 450 can be appropriately
set in a manner of software in the control unit 400b. The
control unit 400b uses the second-order low-pass filter as30
the specific frequency bandpass unit 450. For example, the
power converting apparatus 1b includes the booster unit 150
that boosts a voltage of the direct-current power output
33
from the rectifier unit 130. In a case where the
commercial power supply 110 is a single-phase commercial
power supply, the control unit 400b sets the control band
of the specific frequency bandpass unit 450 to be twice or
lower than the frequency of the single-phase commercial5
power supply. In addition, the control unit 400b
attenuates a 2n-th order component of the frequency of the
single-phase commercial power supply at a rate of -
40dB/decade or more, where n is an integer of two or more,
and controls the operation of the booster unit 150 by using10
the direct-current bus voltage Vdc'.
[0069] A hardware configuration of the control unit 400b
included in the power converting apparatus 1b will be
described. Similarly to the control unit 400 in the first
embodiment, the control unit 400b is implemented by the15
processor 91 and the memory 92.
[0070] As described above, according to the present
embodiment, in the power converting apparatus 1b connected
to the commercial power supply 110 that is a single-phase
commercial power supply, the control unit 400b can improve20
the limitation of the operation region of the magnetic flux
weakening control caused by the pulsatile component by
using a low-pass filter as the specific frequency bandpass
unit 450.
[0071] Fifth Embodiment.25
In the fourth embodiment, the case where the
commercial power supply 110 is a single-phase commercial
power supply has been described as an example of using a
low-pass filter as the specific frequency bandpass unit 450.
In the fifth embodiment, a case where the commercial power30
supply 110a is a three-phase commercial power supply will
be described as an example of using a low-pass filter as
the specific frequency bandpass unit 450.
34
[0072] FIG. 11 is a diagram illustrating a configuration
example of a power converting apparatus 1c according to the
fifth embodiment. The power converting apparatus 1c is
connected to the commercial power supply 110a and the
compressor 315. The power converting apparatus 1c converts5
the first alternating-current power of the power supply
voltage Vs, supplied from the commercial power supply 110a
that is a three-phase commercial power supply, into the
second alternating-current power with desired amplitude and
phase, and supplies the second alternating-current power to10
the compressor 315. The power converting apparatus 1c
includes the reactors 120 to 122, the rectifier unit 130a,
the booster unit 150, the voltage detecting unit 501, the
smoothing unit 200, the inverter 310, the current detecting
units 313a and 313b, and the control unit 400b. Note that15
the power converting apparatus 1c and the motor 314
included in the compressor 315 constitute a motor drive
apparatus 2c.
[0073] The configuration and operation of the control
unit 400b are similar to the configuration and operation of20
the control unit 400b in the fourth embodiment, but the
setting of the specific frequency bandpass unit 450 is
different. As described above, a voltage ripple is
superimposed on a voltage generated in the capacitor 210 by
the smoothing. In a case where the commercial power supply25
110 is a single-phase commercial power supply, the
frequency of the voltage ripple has a primary component
that is twice the frequency of the power supply voltage Vs.
In a case where the commercial power supply 110a is a
three-phase commercial power supply, the frequency of the30
voltage ripple has a primary component that is six times
the frequency of the power supply voltage Vs.
[0074] In the present embodiment, the control unit 400b
35
uses the second-order low-pass filter as the specific
frequency bandpass unit 450. The control unit 400b
eliminates a pulsatile component having a frequency 6n
times the power supply frequency generated in the
commercial power supply 110a from the direct-current bus5
voltage Vdc by using the second-order low-pass filter, and
prevents the superimposition of a low-frequency pulsatile
component on the direct-current bus voltage Vdc'. By using
the direct-current bus voltage Vdc' from which a high-
frequency component, that is, a pulsatile component has10
been eliminated by the second-order low-pass filter, the
control unit 400b can improve the limitation of the
operation region of the magnetic flux weakening control
caused by the pulsatile component, for example.
[0075] In order to simplify the description, similarly15
to the fourth embodiment, the attenuation coefficient ζ is
set to √(2) such that the second-order low-pass filter
becomes the second-order Butterworth filter, but the point
at which the signal becomes -3dB may be changed by
adjusting the cutoff angular frequency ωn and the20
attenuation coefficient ζ. The pulsatile component can be
eliminated from the signal by appropriately designing the
cutoff angular frequency ωn for the frequency component
that is desired to be attenuated. For example, in order to
attenuate the pulsatile component ω6f having a frequency25
six times the power supply frequency generated in the
commercial power supply 110a, the cutoff angular frequency
ωn just needs to be designed to be equal to or lower than
the frequency of the pulsatile component ω6f, having a
frequency six times the power supply frequency. For30
example, if it is desired to attenuate the pulsatile
component ω6f having a frequency six times the power supply
frequency by 99% from the detected direct-current bus
36
voltage Vdc, the cutoff angular frequency ωn just needs to
be designed to be 1/10 the frequency of the pulsatile
component ω6f, having a frequency six times the power
supply frequency.
[0076] By attenuating a pulsatile component of the5
direct-current bus voltage Vdc by using the second-order
low-pass filter, even when the connected power supply is
the commercial power supply 110a that is a three-phase
commercial power supply, the control unit 400b can reduce
the superimposition of the low-frequency component having a10
frequency twice or lower the power supply frequency caused
by an error in voltage detection timing, similarly to the
case where the commercial power supply 110 is a single-
phase commercial power supply. Accordingly, the control
unit 400b can reduce a low-order harmonic of the motor15
current. Therefore, the control unit 400b can acquire an
effect of reducing the conduction loss of the inverter 310
and the copper loss of the motor 314. Furthermore, the
control unit 400b can acquire a noise reduction effect by
eliminating a beat component. As described above, by using20
the direct-current bus voltage Vdc' from which a high-
frequency component, that is, a pulsatile component has
been eliminated by the second-order low-pass filter, the
control unit 400b can improve the limitation of the
operation region of the magnetic flux weakening control25
caused by the pulsatile component, for example. These
effects, such as pulsation eliminating effects achieved by
the second-order low-pass filter, are profound particularly
in a region such as a low-speed high-load range where a
current becomes large, and under an operating condition30
where pulsation of 6n component generated in a direct-
current voltage output from the rectifier unit 130a without
boosting operation is large.
37
[0077] Similarly to the fourth embodiment, the
characteristic of the low-pass filter in a case where the
low-pass filter is used as the specific frequency bandpass
unit 450 can be appropriately set in a manner of software
in the control unit 400b. The control unit 400b uses the5
second-order low-pass filter as the specific frequency
bandpass unit 450. For example, the power converting
apparatus 1c includes the booster unit 150 that boosts a
voltage of the direct-current power output from the
rectifier unit 130a. In a case where the commercial power10
supply 110a is a three-phase commercial power supply, the
control unit 400b sets the control band of the specific
frequency bandpass unit 450 to be six times or lower than
the frequency of the three-phase commercial power supply.
In addition, the control unit 400b attenuates a 6n-th order15
component of the frequency of the three-phase commercial
power supply at a rate of -40dB/decade or more, where n is
an integer of two or more, and controls the operation of
the booster unit 150 by using the direct-current bus
voltage Vdc'.20
[0078] As described above, according to the present
embodiment, in the power converting apparatus 1c connected
to the commercial power supply 110a that is a three-phase
commercial power supply, similarly to the fourth embodiment,
the control unit 400b can improve the limitation of the25
operation region of the magnetic flux weakening control
caused by the pulsatile component by using a low-pass
filter as the specific frequency bandpass unit 450.
[0079] Sixth Embodiment.
In a sixth embodiment, a case will be described where30
the specific frequency bandpass unit 450 includes a
plurality of filters, selects an output from each filter,
and outputs the selected output as the direct-current bus
38
voltage Vdc'. The specific frequency bandpass unit 450 of
the present embodiment can be applied to any power
converting apparatus of the first to fifth embodiments.
Here, as an example, the power converting apparatus 1 in
the first and second embodiments will be described as an5
example.
[0080] FIG. 12 is a block diagram illustrating a
configuration example of the specific frequency bandpass
unit 450 included in the control unit 400 of the power
converting apparatus 1 according to the sixth embodiment.10
The specific frequency bandpass unit 450 includes a first
filter 451, a second filter 452, and a selection unit 453.
[0081] The first filter 451 is an n-th order filter,
where n is an integer of two or more. That is, the first
filter 451 is a filter with a second order or higher. The15
first filter 451 is a high-pass filter in the second and
third embodiments, and is a low-pass filter in the fourth
and fifth embodiments. An FIR filter, an IIR filter, or
the like may be used as the first filter 451.
[0082] The second filter 452 is a first-order filter in20
which n=1. That is, the second filter 452 is a filter with
a smaller order than the first filter 451. The second
filter 452 is a high-pass filter in the second and third
embodiments, and is a low-pass filter in the fourth and
fifth embodiments. An FIR filter, an IIR filter, or the25
like may be used as the second filter 452.
[0083] The selection unit 453 selects an output from the
first filter 451 or an output from the second filter 452
depending on a computing load of the control unit 400. The
selection unit 453 acquires a signal ALM indicating the30
computing load of the control unit 400. The selection unit
453 may acquire the signal ALM indicating the computing
load of the control unit 400 from a configuration (not
39
illustrated) that monitors the processing of the control
unit 400, or from the configuration of the control unit 400
illustrated in FIG. 4 excluding the specific frequency
bandpass unit 450. The signal ALM includes, for example, a
computation time indicating a time required for a defined5
computation, a computation speed indicating a speed of the
defined computation, and the like. The selection unit 453
attenuates a pulsatile component of the direct-current bus
voltage Vdc by using the first filter 451 that is a high-
order filter in an operation region where the computing10
load is light and there is a margin for computation time.
On the other hand, the selection unit 453 selects the
output from the second filter 452 that is a first-order
filter in an operation region where the computing load is
heavy and there is no margin for the computation time.15
Since the specific frequency bandpass unit 450 outputs the
output from the second filter 452 as the direct-current bus
voltage Vdc', the control unit 400 can allocate computation
time to other processes in a case where the computing load
is heavy.20
[0084] Note that, since the specific frequency bandpass
unit 450 uses only the output from one of the first filter
451 and the second filter 452, the computation may be
stopped for the filter whose output is not selected. With
such a configuration, the specific frequency bandpass unit25
450 can further reduce the computing load of the control
unit 400.
[0085] Furthermore, the specific frequency bandpass unit
450 may include a plurality of filters with different
orders as the first filter 451. With such a configuration,30
in a case where the computing load of the control unit 400
becomes heavy, the specific frequency bandpass unit 450 can
switch to the output from the filter with a smaller order
40
in stages according to the value of the signal ALM.
[0086] As described above, according to the present
embodiment, in the power converting apparatus 1, the
specific frequency bandpass unit 450 of the control unit
400 is configured to switch the order of the filter to be5
used depending on the computing load of the control unit
400. With such a configuration, depending on the computing
load of the control unit 400, the specific frequency
bandpass unit 450 can use a high-order filter when there is
a margin for computation time, and can use a low-order10
filter when there is no margin for computation time.
[0087] Seventh Embodiment.
FIG. 13 is a diagram illustrating a configuration
example of a refrigeration-cycle application device 900
according to a seventh embodiment. The refrigeration-cycle15
application device 900 according to the seventh embodiment
includes the power converting apparatus 1 described in the
first and second embodiments. Note that the refrigeration-
cycle application device 900 can include the power
converting apparatus 1a described in the third embodiment,20
the power converting apparatus 1b described in the fourth
embodiment, the power converting apparatus 1c described in
the fifth embodiment, and the like, but here, a case of
including the power converting apparatus 1 will be
described as an example. The refrigeration-cycle25
application device 900 according to the seventh embodiment
can be applied to a product including a refrigeration cycle,
such as an air conditioner, a refrigerator, a freezer, or a
heat pump water heater. Note that, in FIG. 13, constituent
elements having functions similar to those in the first30
embodiment are denoted by the same reference numerals as
those in the first embodiment.
[0088] The refrigeration-cycle application device 900
41
includes the compressor 315 incorporating the motor 314 in
the first embodiment, a four-way valve 902, an indoor heat
exchanger 906, an expansion valve 908, an outdoor heat
exchanger 910, which are mounted to the refrigeration-cycle
application device 900 via a refrigerant pipe 912.5
[0089] Inside the compressor 315, a compression
mechanism 904 that compresses a refrigerant and the motor
314 that operates the compression mechanism 904 are
provided.
[0090] The refrigeration-cycle application device 90010
can perform a heating operation or a cooling operation by a
switching operation of the four-way valve 902. The
compression mechanism 904 is driven by the variable-speed
controlled motor 314.
[0091] During the heating operation, as indicated by15
solid arrows, a refrigerant is pressurized and discharged
by the compression mechanism 904, passes through the four-
way valve 902, the indoor heat exchanger 906, the expansion
valve 908, the outdoor heat exchanger 910, and the four-way
valve 902, and returns to the compression mechanism 904.20
[0092] During the cooling operation, as indicated by
broken arrows, the refrigerant is pressurized and
discharged by the compression mechanism 904, passes through
the four-way valve 902, the outdoor heat exchanger 910, the
expansion valve 908, the indoor heat exchanger 906, and the25
four-way valve 902, and returns to the compression
mechanism 904.
[0093] During the heating operation, the indoor heat
exchanger 906 acts as a condenser and releases heat, and
the outdoor heat exchanger 910 acts as an evaporator and30
absorbs heat. During the cooling operation, the outdoor
heat exchanger 910 acts as a condenser and releases heat,
and the indoor heat exchanger 906 acts as an evaporator and
42
absorbs heat. The expansion valve 908 decompresses and
expands the refrigerant.
[0094] The configurations described in the above
embodiments are just examples and can be combined with
other known techniques. The embodiments can be combined5
with each other and the configurations can be partially
omitted or changed without departing from the gist.
Reference Signs List
[0095] 1, 1a, 1b, 1c power converting apparatus; 2, 2a,10
2b, 2c motor drive apparatus; 110, 110a commercial power
supply; 120 to 122 reactor; 130, 130a rectifier unit; 131
to 136 rectifier element; 150 booster unit; 200
smoothing unit; 210 capacitor; 310 inverter; 311a to 311f
switching element; 312a to 312f freewheeling diode; 313a,15
313b current detecting unit; 314 motor; 315 compressor;
400, 400b control unit; 401 rotor position estimation
unit; 402 speed control unit; 403 magnetic flux weakening
control unit; 404 current control unit; 405, 406
coordinate conversion unit; 407 PWM signal generation20
unit; 408 q-axis current pulsation computing unit; 409
addition unit; 420 subtraction unit; 421 to 424 Fourier
coefficient computing unit; 425 to 428 PID control unit;
429 alternating-current restoration unit; 450 specific
frequency bandpass unit; 451 first filter; 452 second25
filter; 453 selection unit; 501 voltage detecting unit;
900 refrigeration-cycle application device; 902 four-way
valve; 904 compression mechanism; 906 indoor heat
exchanger; 908 expansion valve; 910 outdoor heat
exchanger; 912 refrigerant pipe.30
43
WE CLAIM:
[Claim 1] A power converting apparatus comprising:
a rectifier unit rectifying first alternating-current
power supplied from a commercial power supply;
a capacitor connected to an output end of the5
rectifier unit;
an inverter connected across the capacitor, the
inverter generating second alternating-current power and
outputting the second alternating-current power to a motor;
a detecting unit detecting a first direct-current bus10
voltage, the first direct-current bus voltage being a
voltage across the capacitor; and
a control unit including a specific frequency bandpass
unit passing a defined frequency band among power-supply
pulsatile components contained in the first direct-current15
bus voltage, the control unit controlling an operation of
the inverter and the motor by using a second direct-current
bus voltage, the second direct-current bus voltage being
the first direct-current bus voltage after passing through
the specific frequency bandpass unit.20
[Claim 2] The power converting apparatus according to claim
1, wherein
in a case where the commercial power supply is a
single-phase commercial power supply, the control unit sets25
a control band of the specific frequency bandpass unit to
be twice or lower than a frequency of the single-phase
commercial power supply, and attenuates a second-order or
lower component of the frequency of the single-phase
commercial power supply at a rate of -40dB/decade or more.30
[Claim 3] The power converting apparatus according to claim
1, wherein
44
in a case where the commercial power supply is a
three-phase commercial power supply, the control unit sets
a control band of the specific frequency bandpass unit to
be six times or lower than a frequency of the three-phase
commercial power supply, and attenuates a six-order or5
lower component of the frequency of the three-phase
commercial power supply at a rate of -40dB/decade or more.
[Claim 4] The power converting apparatus according to claim
1, comprising10
a booster unit boosting a voltage of direct-current
power output from the rectifier unit, wherein
in a case where the commercial power supply is a
single-phase commercial power supply, the control unit sets
a control band of the specific frequency bandpass unit to15
be twice or lower than a frequency of the single-phase
commercial power supply, and attenuates a 2n-th order
component of the frequency of the single-phase commercial
power supply at a rate of -40dB/decade or more, where n is
an integer of two or more, and controls an operation of the20
booster unit by using the second direct-current bus voltage.
[Claim 5] The power converting apparatus according to claim
1, comprising
a booster unit boosting a voltage of direct-current25
power output from the rectifier unit, wherein
in a case where the commercial power supply is a
three-phase commercial power supply, the control unit sets
a control band of the specific frequency bandpass unit to
be six times or lower than a frequency of the three-phase30
commercial power supply, and attenuates a 6n-th order
component of the frequency of the three-phase commercial
power supply at a rate of -40dB/decade or more, where n is
45
an integer of two or more, and controls an operation of the
booster unit by using the second direct-current bus voltage.
[Claim 6] The power converting apparatus according to any
one of claims 1 to 5, wherein5
the specific frequency bandpass unit includes:
a first filter with a second order or higher;
a second filter with a smaller order than the first
filter; and
a selection unit selecting an output from the first10
filter or an output from the second filter depending on a
computing load.
[Claim 7] A motor drive apparatus comprising the power
converting apparatus according to any one of claims 1 to 6.15
[Claim 8] A refrigeration-cycle application device
comprising the power converting apparatus according to any
one of claims 1 to 6.