FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
[See section 10, Rule 13]
POWER CONVERSION APPARATUS, MOTOR DRIVE APPARATUS, AND
REFRIGERATION CYCLE APPARATUS;
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
5 conversion apparatus that converts alternating-current
power into desired power and also relates to a motor drive
apparatus and a refrigeration cycle apparatus.
Background
10 [0002] There is a conventional power conversion
apparatus that converts alternating-current power supplied
from an alternating-current power supply into desired
alternating-current power and supplies the desired
alternating-current power to a load in an air conditioner
15 or another apparatus. For example, in a technique
disclosed in Patent Literature 1 for a power conversion
apparatus as a control apparatus for an air conditioner,
alternating-current power supplied from an alternatingcurrent power supply is rectified by a diode stack as a
20 rectification unit and is further smoothed by a smoothing
capacitor. The smoothed power is converted by an inverter
composed of a plurality of switching elements into desired
alternating-current power for output to a compressor motor
as a load.
25
Citation List
Patent Literature
[0003] Patent Literature 1: Japanese Patent Application
Laid-open No. H07-71805
30
Summary
Technical Problem
[0004] However, a problem with the above-described

3
conventional technique is that a large current flows into
the smoothing capacitor, thus accelerating aging
degradation of the smoothing capacitor. To address this
problem, increasing capacitance of the smoothing capacitor
5 for restraining variation of ripple in a capacitor voltage
or using a smoothing capacitor with a greater tolerance to
ripple-induced degradation is a conceivable method but
causes increased costs of capacitor parts and causes the
apparatus to have an increased size.
10 [0005] The present disclosure has been made in view of
the above, and an object of the present disclosure is to
obtain a power conversion apparatus that enables its
increase in size to be restrained while restraining
degradation of a capacitor to be used for smoothing.
15
Solution to Problem
[0006] To solve the problem and achieve the object
described above, a power conversion apparatus according to
the present disclosure includes: a rectification unit
20 rectifying a first alternating-current power supplied from
a commercial power supply; a capacitor connected to output
terminals of the rectification unit; an inverter that is
connected across the capacitor, converts power output from
the rectification unit and the capacitor into a second
25 alternating-current power, and outputs the second
alternating-current power to a load including a motor; and
a control unit performing operation control on the inverter
to cause the second alternating-current power that includes
a pulsation based on a pulsation of power that flows into
30 the capacitor from the rectification unit to be output from
the inverter to the load, to restrain a current that flows
into the capacitor.

4
Advantageous Effects of Invention
[0007] The power conversion apparatus according to the
present disclosure produces effects of enabling its
increase in size to be restrained and restraining
5 degradation of the capacitor that is used for smoothing.
Brief Description of Drawings
[0008] FIG. 1 is a diagram illustrating an exemplary
configuration of a power conversion apparatus according to
10 a first embodiment.
FIG. 2 is a diagram illustrating examples of currents
as well as an example of a capacitor voltage across a
capacitor in a smoothing unit in a comparative example in
which the current output from a rectification unit has been
15 smoothed by the smoothing unit, causing the current that
flows into an inverter to be constant.
FIG. 3 is a diagram illustrating examples of the
currents as well as an example of the capacitor voltage
across the capacitor in the smoothing unit when a control
20 unit of the power conversion apparatus according to the
first embodiment has reduced the current that flows into
the smoothing unit through operation control of the
inverter.
FIG. 4 is a flowchart illustrating the operation of
25 the control unit of the power conversion apparatus
according to the first embodiment.
FIG. 5 is a diagram illustrating an example of a
hardware configuration that implements the control unit of
the power conversion apparatus according to the first
30 embodiment.
FIG. 6 is a diagram illustrating an exemplary
configuration of a refrigeration cycle apparatus according
to a second embodiment.

5
Description of Embodiments
[0009] With reference to the drawings, a detailed
description is hereinafter provided of a power conversion
5 apparatus, a motor drive apparatus, and a refrigeration
cycle apparatus according to embodiments of the present
disclosure.
[0010] First Embodiment.
FIG. 1 is a diagram illustrating an exemplary
10 configuration of a power conversion apparatus 1 according
to a first embodiment. The power conversion apparatus 1 is
connected to a commercial power supply 110 and a compressor
315. The power conversion apparatus 1 converts a first
alternating-current power at a power supply voltage Vs that
15 is supplied from the commercial power supply 110 into a
second alternating-current power having a desired amplitude
and a desired phase and supplies the second alternatingcurrent power to the compressor 315. The power conversion
apparatus 1 includes a voltage and current detection unit
20 501, a reactor 120, a rectification unit 130, a voltage
detection unit 502, a smoothing unit 200, an inverter 310,
current detection units 313a and 313b, and a control unit
400. The power conversion apparatus 1 and a motor 314
included in the compressor 315 compose a motor drive
25 apparatus 2.
[0011] The voltage and current detection unit 501
detects a voltage value and a current value of the first
alternating-current power at the power supply voltage Vs
that is supplied from the commercial power supply 110 and
30 outputs the detected voltage and current values to the
control unit 400. The reactor 120 is connected between the
voltage and current detection unit 501 and the
rectification unit 130. The rectification unit 130

6
includes a bridge circuit composed of rectifier elements
131 to 134, and rectifies the first alternating-current
power at the power supply voltage Vs that is supplied from
the commercial power supply 110 and outputs the power
5 rectified. The rectification unit 130 performs full-wave
rectification. The voltage detection unit 502 detects a
voltage value of the power rectified by the rectification
unit 130 and outputs the detected voltage value to the
control unit 400. The smoothing unit 200 is connected to
10 output terminals of the rectification unit 130 via the
voltage detection unit 502. The smoothing unit 200
includes a capacitor 210 as a smoothing element and smooths
the power rectified by the rectification unit 130.
Examples of the capacitor 210 include an electrolytic
15 capacitor and a film capacitor, among others. The
capacitor 210 has such capacitance as to smooth the power
rectified by the rectification unit 130. The smoothing
causes voltage across the capacitor 210 to not assume a
full-wave rectified waveform of the commercial power supply
20 110, but a waveform that includes a direct-current
component with voltage ripple based on a frequency of the
commercial power supply 110 superimposed and does not
pulsate significantly. A main frequency component of this
voltage ripple is a component that is double the frequency
25 of the power supply voltage Vs when the commercial power
supply 110 is single-phase or six times the frequency of
the power supply voltage Vs when the commercial power
supply 110 is three-phase. If the power input from the
commercial power supply 110 and the power that is output
30 from the inverter 310 do not change, the amplitude of this
voltage ripple is determined by the capacitance of the
capacitor 210. For example, the voltage ripple generated
across the capacitor 210 pulsates in a range such that its

7
maximum value is less than twice its minimum value.
[0012] The inverter 310 is connected across the
smoothing unit 200, namely the capacitor 210. The inverter
310 includes switching elements 311a to 311f and
5 freewheeling diodes 312a to 312f. The inverter 310 turns
on and off the switching elements 311a to 311f under
control of the control unit 400, converts power output from
the rectification unit 130 and the smoothing unit 200 into
the second alternating-current power that has the desired
10 amplitude and the desired phase, and outputs the second
alternating-current power to the compressor 315. Each of
the current detection units 313a and 313b detects a value
of one of three phase currents that are output from the
inverter 310 and outputs the detected current value to the
15 control unit 400. By obtaining the values of the two phase
currents of the values of three phase currents that are
output from the inverter 310, the control unit 400 is
enabled to calculate a value of a remaining one of the
three phase currents that are output from the inverter 310.
20 The compressor 315 is a load including the motor 314 that
drives a compression mechanism. The motor 314 rotates
according to the amplitude and the phase of the second
alternating-current power supplied from the inverter 310,
effecting compression operation. If, for example, the
25 compressor 315 is a hermetic compressor that is used in an
air conditioner or another apparatus, load torque of the
compressor 315 can often be considered a constant torque
load.
[0013] The arrangement of the configurations that is
30 illustrated in FIG. 1 is an example. The power conversion
apparatus 1 is not limited to the example arrangement of
the configurations that is illustrated in FIG. 1. For
example, the reactor 120 may be downstream of the

8
rectification unit 130. In a description below, the
voltage and current detection unit 501, the voltage
detection unit 502, and the current detection units 313a
and 313b may all be referred to as the detection units.
5 The voltage and current values detected by the voltage and
current detection unit 501, the voltage value detected by
the voltage detection unit 502, and the current values
detected by the current detection units 313a and 313b may
be referred to as the detection values.
10 [0014] The control unit 400 obtains the voltage and
current values of the first alternating-current power at
the power supply voltage Vs from the voltage and current
detection unit 501, the voltage value of the power
rectified by the rectification unit 130 from the voltage
15 detection unit 502, and the current values of the second
alternating-current power with the desired amplitude and
the desired phase that has been obtained as a result of the
conversion by the inverter 310 from the current detection
units 313a and 313b. The control unit 400 uses the
20 detection values detected by the detection units in
controlling the operation of the inverter 310 or, more
specifically, the on and off switching of the switching
elements 311a to 311f of the inverter 310. The control
unit 400 according to the present embodiment performs the
25 operation control on the inverter 310 to cause the second
alternating-current power that includes a pulsation based
on a pulsation of the power that flows into the capacitor
210 of the smoothing unit 200 from the rectification unit
130 to be output from the inverter 310 to the compressor
30 315, which is the load. The pulsation based on the
pulsation of the power that flows into the capacitor 210 of
the smoothing unit 200 refers to, for example, a pulsation
that changes depending on, for example, a frequency of the

9
pulsation of the power that flows into the capacitor 210 of
the smoothing unit 200. In this way, the control unit 400
restrains a current that flows into the capacitor 210 of
the smoothing unit 200. The control unit 400 does not have
5 to use all the detection values obtained from the detection
units. The control unit 400 may use part of the detection
values in the control.
[0015] A description is provided next of how the control
unit 400 of the power conversion apparatus 1 operates. In
10 the power conversion apparatus 1 according to the present
embodiment, a load that is generated by the inverter 310
and the compressor 315 can be regarded as the constant load.
A description below is based on the assumption that a
constant current load is connected to the smoothing unit
15 200 when viewed in terms of a current that is output from
the smoothing unit 200. Herein, as illustrated in FIG. 1,
a current that flows from the rectification unit 130 refers
to the current I1, a current that flows into the inverter
310 refers to the current I2, and the current that flows
20 from the smoothing unit 200 refers to the current I3. The
current I2 is the current as a combination of the current
I1 and the current I3. The current I3 can be expressed as
a difference between the current I2 and the current I1,
that is to say, the current I2 minus the current I1. The
25 current I3 has a positive direction in a discharge
direction of the smoothing unit 200 and a negative
direction in a charge direction of the smoothing unit 200.
In other words, there are cases where the current flows
into and flows out of the smoothing unit 200.
30 [0016] FIG. 2 is a diagram illustrating examples of the
currents I1 to I3 and an example of a capacitor voltage Vdc
across the capacitor 210 in the smoothing unit 200 in a
comparative example in which the current output from the

10
rectification unit 130 has been smoothed by the smoothing
unit 200, causing the current I2 that flows into the
inverter 310 to be constant. The current I1, the current
I2, the current I3, and the capacitor voltage Vdc that is
5 generated across the capacitor 210 in accordance with the
current I3 are illustrated from the top in this order. A
vertical axis for each of the currents I1, I2, and I3
represents a current value, and a vertical axis for the
capacitor voltage Vdc represents a voltage value. Every
10 horizontal axis represents time t. Although a carrier
component of the inverter 310 is actually superimposed on
the currents I2 and I3, this is omitted here. The same
applies to what follows. As illustrated in FIG. 2, if the
current I1 that flows from the rectification unit 130 has
15 been smoothed enough by the smoothing unit 200 in the power
conversion apparatus 1, the current I2 that flows into the
inverter 310 becomes a constant current value. However,
the current I3 that flows into the capacitor 210 of the
smoothing unit 200 is large and causes degradation of the
20 capacitor 210. Therefore, the control unit 400 of the
power conversion apparatus 1 according to the present
embodiment controls the current I2 that flows into the
inverter 310, that is to say, controls the operation of the
inverter 310 in order to reduce the current I3 that flows
25 into the smoothing unit 200.
[0017] FIG. 3 is a diagram illustrating examples of the
currents I1 to I3 and an example of the capacitor voltage
Vdc across the capacitor 210 in the smoothing unit 200 when
the control unit 400 of the power conversion apparatus 1
30 according to the first embodiment has reduced the current
I3 that flows into the smoothing unit 200 through the
operation control of the inverter 310. The current I1, the
current I2, the current I3, and the capacitor voltage Vdc

11
that is generated across the capacitor 210 in accordance
with the current I3 are illustrated from the top in this
order. A vertical axis for each of the currents I1, I2,
and I3 represents the current value, and a vertical axis
5 for the capacitor voltage Vdc represents the voltage value.
Every horizontal axis represents time t. Through the
operation control of the inverter 310 to cause the current
I2, such as illustrated in FIG. 3, to flow into the
inverter 310, the control unit 400 of the power conversion
10 apparatus 1 is capable of reducing frequency components in
the current that flows into the smoothing unit 200 from the
rectification unit 130, thus reducing the current I3 that
flows into the smoothing unit 200, as compared with the
example of FIG. 2. Specifically, the control unit 400
15 performs the operation control on the inverter 310 to cause
the current I2 that includes a pulsating current whose main
component is a frequency component of the current I1 to
flow into the inverter 310.
[0018] The frequency component of the current I1 is
20 determined by a frequency of an alternating current
supplied from the commercial power supply 110 and the
configuration of the rectification unit 130. Therefore,
the control unit 400 enables a frequency component of the
pulsating current that is superimposed on the current I2 to
25 be a component having a predetermined amplitude and a
predetermined phase. The frequency component of the
pulsating current that is superimposed on the current I2
has a waveform similar to that of the frequency component
of the current I1. As the control unit 400 brings the
30 frequency component of the pulsating current that is
superimposed on the current I2 closer to the frequency
component of the current I1, the control unit 400 enables
the current I3 that flows into the smoothing unit 200 to

12
reduce and enables a pulsating voltage that is generated in
the capacitor voltage Vdc to reduce.
[0019] The pulsation control of the current that flows
into the inverter 310 by the control unit 400 through the
5 operation control of the inverter 310 is equivalent to
pulsation control of the first alternating-current power
that is output from the inverter 310 to the compressor 315.
Through the operation control of the inverter 310, the
control unit 400 causes the pulsation included in the
10 second alternating-current power that is output from the
inverter 310 to become smaller than the pulsation of the
power that is output from the rectification unit 130. In
order for the voltage ripple of the capacitor voltage Vdc,
namely the voltage ripple generated across the capacitor
15 210 to be smaller than voltage ripple that will be
generated across the capacitor 210 if the second
alternating-current power that is output from the inverter
310 does not include the pulsation based on the pulsation
of the power that flows into the capacitor 210, the control
20 unit 400 performs amplitude and phase control on the
pulsation included in the second alternating-current power
that is output from the inverter 310. Alternatively, in
order for current ripple that flows into and out of the
capacitor 210 to be smaller than current ripple that will
25 be generated through the capacitor 210 if the second
alternating-current power that is output from the inverter
310 does not include the pulsation based on the pulsation
of the power that flows into the capacitor 210, the control
unit 400 performs the amplitude and phase control on the
30 pulsation included in the second alternating-current power
that is output from the inverter 310. The case where the
second alternating-current power that is output from the
inverter 310 does not include the pulsation based on the

13
pulsation of the power that flows into the capacitor 210
refers to control, such as illustrated in FIG. 2.
[0020] The alternating current that is supplied from the
commercial power supply 110 is not particularly limited and
5 may be single-phase or three-phase. The control unit 400
only has to determine the frequency component of the
pulsating current that is superimposed on the current I2 on
the basis of the first alternating-current power that is
supplied from the commercial power supply 110.
10 Specifically, the control unit 400 controls a pulsating
waveform of the current I2 that flows into the inverter 310
to a shape obtained by adding a direct-current component to
a pulsating waveform whose main component is a frequency
component that is double a frequency of the first
15 alternating-current power if the first alternating-current
power that is supplied from the commercial power supply 110
is single-phase or six times the frequency of the first
alternating-current power if the first alternating-current
power that is supplied from the commercial power supply 110
20 is three-phase. The pulsating waveform is, for example, a
shape defined by absolute values of a sine wave or sine
wave-shaped. In this case, the control unit 400 may add at
least one of frequency components that are integer
multiples of a frequency of the sine wave as a prespecified
25 amplitude to the pulsating waveform. The pulsating
waveform may be rectangular wave-shaped or triangular-wave
shaped. In this case, the control unit 400 may set
amplitude and phase of the pulsating waveform as
prespecified values.
30 [0021] The control unit 400 may use the voltage across
the capacitor 210 or the current flowing into the capacitor
210 in calculating a pulsating quantity of the pulsation to
be included in the second alternating-current power, which

14
is output from the inverter 310, or may use the voltage or
the current of the first alternating-current power supplied
from the commercial power supply 110 in calculating a
pulsating quantity of the pulsation to be included in the
5 second alternating-current power, which is output from the
inverter 310.
[0022] With reference to a flowchart, a description is
provided of the operation of the control unit 400. FIG. 4
is a flowchart illustrating the operation of the control
10 unit 400 of the power conversion apparatus 1 according to
the first embodiment. The control unit 400 obtains
detection values from the detection units of the power
conversion apparatus 1 (step S1). On the basis of the
obtained detection values, the control unit 400 performs,
15 on the inverter 310, the operation control to reduce the
current I3 that flows into the smoothing unit 200 (step S2).
[0023] A description is provided next of a hardware
configuration of the control unit 400 of the power
conversion apparatus 1. FIG. 5 is a diagram illustrating
20 an example of the hardware configuration that implements
the control unit 400 of the power conversion apparatus 1
according to the first embodiment. The control unit 400 is
implemented with a processor 91 and a memory 92.
[0024] The processor 91 is a central processing unit
25 (CPU) (also referred to as a processing unit, an arithmetic
unit, a microprocessor, a microcomputer, a processor, or a
digital signal processor (DSP)) or a system large-scale
integration (LSI). The memory 92 is, for example, a
nonvolatile or volatile semiconductor memory such as a
30 random-access memory (RAM), a read-only memory (ROM), a
flash memory, an erasable programmable read-only memory
(EPROM), or an electrically erasable programmable read-only
memory (EEPROM) (registered trademark). The memory 92 is

15
not limited to these and may be a magnetic disk, an optical
disk, a compact disk, a mini disk, or a digital versatile
disc (DVD).
[0025] As described above, according to the present
5 embodiment, the control unit 400 of the power conversion
apparatus 1 performs the operation control on the inverter
310 on the basis of the detection values obtained from the
detection units to superimpose the pulsating frequency
component based on the frequency component of the current
10 I1 flowing from the rectification unit 130 on the current
I2 that flows into the inverter 310, thus reducing the
current I3 that flows into the smoothing unit 200. Since
the current I3 that flows into the smoothing unit 200 is
reduced thus, the power conversion apparatus 1 is enabled
15 to use a capacitor with a smaller tolerance to ripple
current than in a case where the control according to the
present embodiment is not performed. Since the power
conversion apparatus 1 reduces the pulsating voltage in the
capacitor voltage Vdc, the capacitor 210 to be installed is
20 enabled to have a smaller capacitance than in the case
where the control according to the present embodiment is
not performed. In cases where, for example, the smoothing
unit 200 includes a plurality of the capacitors 210, the
power conversion apparatus 1 enables the smoothing unit 200
25 to have a reduced number of capacitors 210.
[0026] Since the pulsation included in the second
alternating-current power is caused, through the operation
control of the inverter 310, to become smaller than the
pulsation of the power that is output from the
30 rectification unit 130, the power conversion apparatus 1
enables the pulsating component superimposed on the current
I2 that flows into the inverter 310 to be restrained from
becoming excessive. Superimposing the pulsating component

16
increases an effective value of the current that passes
through, for example, the inverter 310 and the motor 314
compared to a state in which the pulsating component is not
superimposed. However, the pulsating component to be
5 superimposed is restrained from becoming excessive, thus
enabling provision of a system that restrains current
capacity of the inverter 310, loss increase in the inverter
310 and loss increase in the motor 314, among others.
[0027] With the control according to the present
10 embodiment, the power conversion apparatus 1 is capable of
restraining vibration of the compressor 315 that is caused
by the pulsation of the current I2.
[0028] Second Embodiment.
FIG. 6 is a diagram illustrating an exemplary
15 configuration of a refrigeration cycle apparatus 900
according to a second embodiment. The refrigeration cycle
apparatus 900 according to the second embodiment includes
the power conversion apparatus 1 described in the first
embodiment. The refrigeration cycle apparatus 900
20 according to the second embodiment is applicable to a
product with a refrigeration cycle, such as an air
conditioner, a refrigerator, a freezer, or a heat pump
water heater. In FIG. 6, constituent elements with the
same functions as those in the first embodiment have the
25 same reference characters as in the first embodiment.
[0029] The refrigeration cycle apparatus 900 has the
compressor 315 with the internal motor 314 in the first
embodiment, a four-way valve 902, an indoor heat exchanger
906, an expansion valve 908, and an outdoor heat exchanger
30 910 connected via refrigerant piping 912.
[0030] The compressor 315 internally includes a
compression mechanism 904 that compresses a refrigerant and
the motor 314 that runs the compression mechanism 904.

17
[0031] The refrigeration cycle apparatus 900 is capable
of operating for heating or cooling through switching
operation of the four-way valve 902. The compression
mechanism 904 is driven by the motor 314 that is controlled
5 at variable speed.
[0032] In the operation for heating, as indicated by
solid line arrows, the refrigerant is pressurized and
discharged by the compression mechanism 904 and returns to
the compression mechanism 904 through the four-way valve
10 902, the indoor heat exchanger 906, the expansion valve 908,
the outdoor heat exchanger 910, and the four-way valve 902.
[0033] In the operation for cooling, as indicated by
dashed line arrows, the refrigerant is pressurized and
discharged by the compression mechanism 904 and returns to
15 the compression mechanism 904 through the four-way valve
902, the outdoor heat exchanger 910, the expansion valve
908, the indoor heat exchanger 906, and the four-way valve
902.
[0034] In the operation for heating, the indoor heat
20 exchanger 906 acts as a condenser to release heat, and the
outdoor heat exchanger 910 acts as an evaporator to absorb
heat. In the operation for cooling, the outdoor heat
exchanger 910 acts as a condenser to release heat, and the
indoor heat exchanger 906 acts as an evaporator to absorb
25 heat. The expansion valves 908 depressurizes and expands
the refrigerant.
[0035] The above configurations illustrated in the
embodiments are illustrative, can be combined with other
techniques that are publicly known, and can be partly
30 omitted or changed without departing from the gist. The
embodiments can be combined together.
Reference Signs List

18
[0036] 1 power conversion apparatus; 2 motor drive
apparatus; 110 commercial power supply; 120 reactor; 130
rectification unit; 131 to 134 rectifier element; 200
smoothing unit; 210 capacitor; 310 inverter; 311a to 311f
5 switching element; 312a to 312f freewheeling diode; 313a,
313b current detection unit; 314 motor; 315 compressor;
400 control unit; 501 voltage and current detection unit;
502 voltage detection unit; 900 refrigeration cycle
apparatus; 902 four-way valve; 904 compression mechanism;
10 906 indoor heat exchanger; 908 expansion valve; 910
outdoor heat exchanger; 912 refrigerant piping.

19
We Claim:
[Claim 1] A power conversion apparatus comprising:
5 a rectification unit rectifying a first alternatingcurrent power supplied from a commercial power supply;
a capacitor connected to output terminals of the
rectification unit;
an inverter that is connected across the capacitor,
10 converts power output from the rectification unit and the
capacitor into a second alternating-current power, and
outputs the second alternating-current power to a load
including a motor; and
a control unit performing operation control on the
15 inverter to cause the second alternating-current power that
includes a pulsation based on a pulsation of power that
flows into the capacitor from the rectification unit to be
output from the inverter to the load, to restrain a current
that flows into the capacitor.
20
[Claim 2] The power conversion apparatus according to claim
1, wherein
the control unit performs operation control on the
inverter to cause a pulsation included in the second
25 alternating-current power that is output from the inverter
to become smaller than a pulsation of power that is output
from the rectification unit.
[Claim 3] The power conversion apparatus according to claim
30 1 or 2, wherein
the control unit performs amplitude and phase control
on a pulsation included in the second alternating-current
power that is output from the inverter to cause voltage

20
ripple generated across the capacitor to be smaller than
voltage ripple that is generated across the capacitor if
the second alternating-current power that is output from
the inverter does not include a pulsation based on a
5 pulsation of power that flows into the capacitor.
[Claim 4] The power conversion apparatus according to claim
1 or 2, wherein
the control unit performs amplitude and phase control
10 on a pulsation included in the second alternating-current
power that is output from the inverter to cause current
ripple that flows into and out of the capacitor to be
smaller than current ripple that is generated through the
capacitor if the second alternating-current power that is
15 output from the inverter does not include a pulsation based
on a pulsation of power that flows into the capacitor.
[Claim 5] The power conversion apparatus according to any
one of claims 1 to 4, wherein
20 the control unit controls a pulsating waveform of a
current that flows into the inverter to a shape obtained by
adding a direct-current component to a pulsating waveform
including as a main component a frequency component that is
double a frequency of the first alternating-current power
25 if the first alternating-current power is single-phase or
six times a frequency of the first alternating-current
power if the first alternating-current power is three-phase.
[Claim 6] The power conversion apparatus according to claim
30 5, wherein
the pulsating waveform is a shape defined by absolute
values of a sine wave or sine-wave shaped.

21
[Claim 7] The power conversion apparatus according to claim
6, wherein
the control unit adds at least one of frequency
components that are integer multiples of a frequency of the
5 sine wave as a specified amplitude to the pulsating
waveform.
[Claim 8] The power conversion apparatus according to claim
5, wherein
10 the pulsating waveform is rectangular wave-shaped or
triangular-wave shaped.
[Claim 9] The power conversion apparatus according to claim
8, wherein
15 the control unit sets an amplitude and a phase of the
pulsating waveform as specified values.
[Claim 10] The power conversion apparatus according to
any one of claims 1 to 9, wherein
20 the control unit uses a voltage across the capacitor
or a current that flows into the capacitor in calculating a
pulsating quantity of a pulsation to be included in the
second alternating-current power that is output from the
inverter.
25
[Claim 11] The power conversion apparatus according to
any one of claims 1 to 9, wherein
the control unit uses a voltage or a current of the
first alternating-current power in calculating a pulsating
30 quantity of a pulsation to be included in the second
alternating-current power that is output from the inverter.
[Claim 12] The power conversion apparatus according to

22
any one of claims 1 to 11, wherein
the capacitor is an electrolytic capacitor or a film
capacitor.
5 [Claim 13] The power conversion apparatus according to
any one of claims 1 to 12, wherein
voltage ripple generated across the capacitor has a
maximum value less than twice a minimum value of the
voltage ripple.
10
[Claim 14] The power conversion apparatus according to
any one of claims 1 to 13, wherein
the rectification unit performs full-wave
rectification, and a voltage generated across the capacitor
15 assumes a shape that is not a full-wave rectified waveform
of the commercial power supply.
[Claim 15] A motor drive apparatus comprising the power
conversion apparatus according to any one of claims 1 to 14.
20
[Claim 16] A refrigeration cycle apparatus comprising
the power conversion apparatus according to any one of
claims 1 to 14.