Electric power conversion apparatus

Abstract

An electric power conversion apparatus (10) is provided with an inverter circuit (13) that is connected in parallel with a capacitor (C), has switching elements (Su, Sv, Sw, Sx, Sy, Sz), and suppresses LC resonance of a circuit including the capacitor (C) and a reactor (L). The inverter circuit (13) is controlled by a control unit (40) so that the integral value of the current flowing from the capacitor (C) to the inverter circuit (13) is 0 or lower in a period that is a half period of the LC resonance starting from a transition timing for a transition from a non-conduction period during which no current flows from an AC power supply (20) to a converter circuit (11) to a conduction period during which a current flows from the AC power supply (20) to the converter circuit (11).

Description

Power Conversion Device

[0001] The present disclosure relates to a power conversion device that converts power output from an AC power supply and supplies the converted power to a load.

[0002] The power conversion device disclosed in Patent Document 1 includes a rectifier circuit that rectifies and outputs AC output from an AC power source, an inverter circuit having a plurality of switching elements that converts the DC output from the rectifier circuit into AC by switching the switching elements and supplies the AC to a load, a DC link capacitor connected between input nodes of the inverter circuit and having a capacitance value set to allow fluctuations in the output voltage of the rectifier circuit and suppress ripple voltage caused by the switching operation, a reactor connected between the AC power source and the rectifier circuit, and a control unit that controls the inverter circuit. In this power conversion device, the control unit controls the inverter circuit to have a non-conduction period during which no current flows from the AC power source to the rectifier circuit, thereby reducing the modulus of the RMS current.

[0003] Patent No. 6566105

[0004] However, in Patent Document 1, immediately after the transition from the non-conduction period to the conduction period in which current flows from the AC power supply to the rectifier circuit, LC resonance occurs in the circuit including the DC link capacitor and the reactor, causing harmonic components to be superimposed on the power supply current flowing from the AC power supply to the rectifier circuit.

[0005] The present disclosure has been made in light of the above-mentioned problem, and aims to suppress harmonics generated in a power supply current due to LC resonance in a circuit including a DC link capacitor and a reactor.

[0006] A first aspect of the present disclosure includes a rectifier circuit (11) that rectifies and outputs AC output from a single-phase AC power supply (20), a first inverter circuit (13) having a plurality of switching elements (Su, Sv, Sw, Sx, Sy, Sz) and converting the DC output from the rectifier circuit (11) into AC by switching operations of the switching elements (Su, Sv, Sw, Sx, Sy, Sz) and supplying the AC output to a first load (30), a DC link capacitor (C) that is connected between input nodes of the first inverter circuit (13) and that has a capacitance value set to allow fluctuations in the output voltage of the rectifier circuit (11) and suppress ripple voltage caused by the switching operations, a reactor (L) that is connected between the rectifier circuit (11) and the first inverter circuit (13) or between the AC power supply (20) and the rectifier circuit (11), and a DC link capacitor (C) that is connected between the ... AC power supply (20) and a first load (30). and a control unit (40) that controls the first inverter circuit (13) so as to have a non-conduction period in which no current flows through the rectifier circuit (11), and further includes a resonance suppression unit (13, 14) that is connected in parallel with the DC link capacitor (C) and has at least one switching element (Su, Sv, Sw, Sx, Sy, Sz, 141) and suppresses LC resonance of a circuit including the DC link capacitor (C) and the reactor (L), wherein the control unit (40) controls the resonance suppression unit (13, 14) so ​​that an integral value of a current flowing from the DC link capacitor (C) to the resonance suppression unit (13, 14) becomes equal to or less than 0 during a half-cycle period (T1) of the LC resonance, the half-cycle period starting from a transition timing (t1) at which the non-conduction period transitions to a conduction period in which current flows from the AC power source (20) to the rectifier circuit (11).

[0007] In the first mode, the integral value of the current flowing from the DC link capacitor (C) to the resonance suppression unit (13, 14) is controlled to be equal to or less than 0 during the half cycle period of the LC resonance starting from the transition timing (t1). Therefore, the power supply current (i in ) harmonics can be suppressed.

[0008] A second aspect of the present disclosure is characterized in that, in the first aspect, the control unit (40) controls the resonance suppression unit (13, 14) so ​​that the current flowing from the DC link capacitor (C) to the resonance suppression unit (13, 14) is equal to or less than 0 at the transition timing (t1).

[0009] In the second mode, at the transition timing (t1), the current flowing from the DC link capacitor (C) to the resonance suppression unit (13, 14) is set to 0 or less, so that the power supply current (i in ) harmonics can be suppressed.

[0010] A third aspect of the present disclosure is characterized in that, in the first or second aspect, the resonance suppression unit (13, 14) is the first inverter circuit (13), and the first load (30) is a motor (30).

[0011] A fourth aspect of the present disclosure is the third aspect, characterized in that the motor (30) is a motor (30) for a compressor.

[0012] A fifth aspect of the present disclosure is characterized in that, in the first or second aspect, a resonance suppression circuit (14) is provided which has a capacitance element (143) and a switching element (141) for a resonance suppression circuit connected in series with each other and is connected in parallel with the DC link capacitor (C), the resonance suppression unit (13, 14) is the resonance suppression circuit (14), and the control unit (40) sets the transition timing (t1) to a timing when the voltage of the capacitance element (143) is higher than the voltage of the DC link capacitor (C).

[0013] In the fifth aspect, by turning on the resonance suppression circuit switching element (141), a current can be caused to flow from the capacitance element (143) to the DC link capacitor (C).

[0014] A sixth aspect of the present disclosure is the fifth aspect, characterized in that the resonance suppression circuit (14) further includes a diode (144) connected in parallel with the resonance suppression circuit switching element (141) with its cathode facing the capacitance element (143).

[0015] In the sixth aspect, when the resonance suppression circuit switching element (141) is turned off, the diode (144) can prevent a current from flowing out of the capacitance element (143) and a voltage drop across the capacitance element (143). Furthermore, when the resonance suppression circuit switching element (141) is turned off, the capacitance element (143) is charged via the diode (144), thereby making the voltage across the capacitance element (143) higher than the voltage across the DC link capacitor (C).

[0016] A seventh aspect of the present disclosure is the fifth or sixth aspect, characterized in that a second inverter circuit (145) is connected to the capacitive element (143) to convert the voltage of the capacitive element (143) into AC and supply the AC voltage to a second load (60) different from the first load (30).

[0017] In the seventh aspect, the energy stored in the capacitance element (143) can be supplied to the second load (60).

[0018] An eighth aspect of the present disclosure is any one of the first to fourth aspects, wherein the control unit (40) controls the voltage (v dc The resonance suppressor (13, 14) is controlled based on the detected value of the temperature.

[0019] A ninth aspect of the present disclosure provides a power supply including: a rectifier circuit (11) that rectifies and outputs AC output from a single-phase AC power supply; an inverter circuit (13) having a plurality of switching elements (Su, Sv, Sw, Sx, Sy, Sz) that converts DC output from the rectifier circuit (11) into AC by switching operations of the switching elements (Su, Sv, Sw, Sx, Sy, Sz) and supplies the AC to a load (30); a DC link capacitor (C) that is connected between input nodes of the inverter circuit (13) and that has a capacitance value set to allow fluctuations in the output voltage of the rectifier circuit (11) and suppress ripple voltage caused by the switching operations; a reactor (L) that is connected between the rectifier circuit (11) and the inverter circuit (13) or between the AC power supply (20) and the rectifier circuit (11); and a control unit (40) that controls the inverter circuit (13) so that a non-conduction period occurs during which no current flows, the power conversion device further comprising a resonance suppression unit (13, 14) that is connected in parallel with the DC link capacitor (C) and has at least one switching element (Su, Sv, Sw, Sx, Sy, Sz, 141, 145a) and that suppresses LC resonance of a circuit including the DC link capacitor (C) and the reactor (L), wherein the control unit (40) operates the resonance suppression unit (13, 14) to attenuate by more than 80% a physical quantity that correlates to pulsation of magnetic energy of the reactor (L) due to the LC resonance during a resonance suppression period of three cycles of the LC resonance, starting from a transition timing (t1) at which the non-conduction period transitions to a conduction period during which current flows from the AC power supply (20) to the rectifier circuit (11).

[0020] In the ninth aspect, during the three-cycle period of the LC resonance starting from the transition timing (t1), the physical quantity correlated with the pulsation of the magnetic energy of the reactor (L) due to the LC resonance is attenuated by more than 80%, so that the power supply current (i in ) harmonics can be suppressed.

[0021] A tenth aspect of the present disclosure provides a rectifier circuit (11) that rectifies and outputs AC output from a three-phase AC power supply (20); an inverter circuit (13) having a plurality of switching elements (Su, Sv, Sw, Sx, Sy, Sz) that converts the DC output from the rectifier circuit (11) into AC by switching operations of the switching elements (Su, Sv, Sw, Sx, Sy, Sz) and supplies the AC to a load; a DC link capacitor (C) that is connected between input nodes of the inverter circuit (13) and that has a capacitance value that allows fluctuations in the output voltage of the rectifier circuit (11) and suppresses ripple voltage caused by the switching operations; a reactor (L) that is connected between the rectifier circuit (11) and the inverter circuit (13) or between the AC power supply (20) and the rectifier circuit (11); and a control unit (40) that controls the inverter circuit (13) so that a non-conduction period exists during which a current of a predetermined phase does not flow, the power conversion device further comprising a resonance suppression unit (13, 14) that is connected in parallel with the DC link capacitor (C) and has at least one switching element (Su, Sv, Sw, Sx, Sy, Sz, 141, 145a) and that suppresses LC resonance of a circuit including the DC link capacitor (C) and the reactor (L), wherein the control unit (40) operates the resonance suppression unit (13, 14) to attenuate by more than 80% a physical quantity that correlates with pulsation of magnetic energy of the reactor (L) due to the LC resonance during a resonance suppression period of three cycles of the LC resonance, starting from a transition timing (t1) at which the non-conduction period transitions to a conduction period during which a current of the predetermined phase flows from the AC power supply (20) to the rectifier circuit (11).

[0022] In the tenth aspect, during the three-cycle period of the LC resonance starting from the transition timing (t1), the physical quantity correlated with the pulsation of the magnetic energy of the reactor (L) due to the LC resonance is attenuated by more than 80%, so that the power supply current (i in ) harmonics can be suppressed.

[0023] An eleventh aspect of the present disclosure is the ninth or tenth aspect, characterized in that the physical quantity is the amplitude of a current flowing through the reactor (L) during the resonance suppression period.

[0024] In the eleventh aspect, during the three-cycle period of the LC resonance starting from the transition timing (t1), the amplitude of the current due to the LC resonance among the currents flowing through the reactor (L) is attenuated by more than 80%, so that the power supply current (i in ) harmonics can be suppressed.

[0025] A twelfth aspect of the present disclosure includes a rectifier circuit (11) that rectifies and outputs AC output from a three-phase AC power supply (20), an inverter circuit (13) having a plurality of switching elements (Su, Sv, Sw, Sx, Sy, Sz) and converting the DC output from the rectifier circuit (11) into AC by switching operations of the switching elements (Su, Sv, Sw, Sx, Sy, Sz) and supplying the AC output to a load (30), a DC link capacitor (C) connected between input nodes of the inverter circuit (13) and having a capacitance value set to allow fluctuations in the output voltage of the rectifier circuit (11) and suppress ripple voltage caused by the switching operations, a reactor (L) connected between the rectifier circuit (11) and the inverter circuit (13) or between the AC power supply (20) and the rectifier circuit (11), and a DC link capacitor (C) connected between the ... AC power supply (20) and the rectifier circuit (11). and a control unit (40) that controls the inverter circuit (13) to have a non-conduction period during which a current of a predetermined phase among the three phases does not flow, and further includes a resonance suppression unit (13, 14) that is connected in parallel with the DC link capacitor (C) and has at least one switching element (Su, Sv, Sw, Sx, Sy, Sz, 141) and suppresses LC resonance of a circuit including the DC link capacitor (C) and the reactor (L), wherein the control unit (40) controls the resonance suppression unit (13, 14) so ​​that an integral value of a current flowing from the DC link capacitor (C) to the resonance suppression unit (13, 14) becomes equal to or less than 0 during a half-cycle period of the LC resonance, the half-cycle period starting from a transition timing (t1) at which the non-conduction period transitions to a conduction period during which a current of the predetermined phase flows from the AC power supply (20) to the rectifier circuit (11).

[0026] In the twelfth aspect, the integral value of the current flowing from the DC link capacitor (C) to the resonance suppression unit (13, 14) is controlled to be equal to or less than 0 during the half cycle period of the LC resonance starting from the transition timing (t1). Therefore, the power supply current (i in ) harmonics can be suppressed.

[0027] FIG. 1 is a block diagram showing the configuration of a power conversion device according to a first embodiment. FIG. 2 shows an example of a waveform of a power supply current. FIG. 3 shows an example of a waveform of a power supply voltage and a DC voltage. FIG. 4 shows the waveforms of a power supply voltage and a DC voltage under conditions 1 to 3. FIG. 5 shows the waveform of a power supply current under conditions 1 to 3. FIG. 6 shows an example of waveforms of a power supply voltage, a DC voltage, and an inverter current before and after a transition timing in the first embodiment. FIG. 7 is a diagram equivalent to FIG. 6 when the inverter current at the transition timing is set to a positive value. FIG. 8 shows the waveform of a current flowing through a reactor due to LC resonance when the damping coefficient is 1000. FIG. 9 is an enlarged view of the X portion of FIG. 8. FIG. 10 is a graph showing the relationship between the damping ratio and the ratio of harmonics to harmonics when the damping ratio is 0. FIG. 11 is a diagram equivalent to FIG. 1 of a second embodiment. FIG. 12 is a block diagram showing the configuration of a repetitive control unit. FIG. 13 is a diagram equivalent to FIG. 1 of a third embodiment. Fig. 14 shows waveforms of a DC voltage, a DC voltage command value, a power supply voltage, a compensation amount generated by feedback control of the DC voltage, and a compensation amount generated by repetitive control of the DC voltage in embodiment 3. Fig. 15 shows a power supply current, a power supply current command value, an inverter current, and a q-axis current in embodiment 3. Fig. 16 is a diagram corresponding to Fig. 1 in embodiment 4. Fig. 17 shows waveforms of a DC link voltage, a power supply voltage, and a voltage of a resonance suppression circuit in embodiment 4. Fig. 18 is a diagram corresponding to Fig. 1 in embodiment 5.

[0028] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. Note that the following embodiments are essentially preferred examples and are not intended to limit the scope of the present invention, its applications, or its uses.

[0029] First Embodiment Fig. 1 shows the configuration of a power conversion device (10) according to a first embodiment of the present disclosure. The power conversion device (10) converts an input AC voltage (in this example, a power supply voltage (v in) into a predetermined output AC voltage and supplies it to a motor (30) serving as a first load. In this embodiment, as shown in FIG. 1 , the power conversion device (10) includes a reactor (L), a converter circuit (11), a DC link unit (12), an inverter circuit (13), and a control unit (40). The motor (30) is, for example, an interior permanent magnet motor (IPM motor), and in this embodiment, drives a compressor (not shown) of an air conditioner.

[0030] <Reactor> The reactor (L) is connected between the AC power supply (20) and one of the input nodes of the converter circuit (11).

[0031] <Converter Circuit> The converter circuit (11) is a rectifier circuit that is connected to the AC power supply (20) via a reactor (L) and that full-wave rectifies and outputs the AC output from the AC power supply (20). In this example, the converter circuit (11) includes four diodes (D1, D2, D3, D4) connected in a bridge configuration. That is, the converter circuit (11) is configured as a diode bridge circuit.

[0032] The DC link unit (12) has a capacitor (C) as a DC link capacitor connected between a pair of input nodes of the inverter circuit (13), and is connected to the output of the converter circuit (11) (i.e., the full-wave rectified power supply voltage (v in )) to generate a DC voltage (v dc ) to generate a DC voltage (v dc ) is the power supply voltage (v in ) pulsates according to the frequency of the DC voltage (v dc ) is the voltage across the capacitor (C).

[0033] Here, the power supply voltage (v in ) is a pulsating component according to the frequency of the DC voltage (v dc) will be explained. The capacitance value of the capacitor (C) of the DC link unit (12) is set so as to tolerate fluctuations in the output of the converter circuit (11) and to suppress ripple voltage (voltage fluctuations according to the switching frequency) caused by the switching operation (described later) of the inverter circuit (13). Specifically, the capacitor (C) is a small-capacity capacitor (e.g., a film capacitor) having a capacitance value (e.g., several tens of μF) that is approximately 0.01 times the capacitance value of a smoothing capacitor (e.g., an electrolytic capacitor) used to smooth the output of the converter circuit in a general power conversion device. Because the capacitor (C) is configured in this way, the output of the converter circuit (11) is hardly smoothed in the DC link unit (12), and as a result, the power supply voltage (v in ) frequency pulsating component (in this example, the power supply voltage (v in ) is a pulsating component with a frequency twice that of the DC voltage (v dc ) remains. For example, the DC voltage (v dc ) pulsates so that its maximum value is more than twice its minimum value.

[0034] <Inverter Circuit> The inverter circuit (13) has six bridge-connected switching elements (Su, Sv, Sw, Sx, Sy, Sz) and six freewheeling diodes (Du, Dv, Dw, Dx, Dy, Dz) to supply a three-phase output AC voltage to the motor (30). More specifically, the inverter circuit (13) has three switching legs, each of which has two switching elements connected in series. In each of the three switching legs, a midpoint between an upper-arm switching element (Su, Sv, Sw) and a lower-arm switching element (Sx, Sy, Sz) is connected to a coil of each phase (u-phase, v-phase, w-phase coil) of the motor (30). The six switching elements (Su, Sv, Sw, Sx, Sy, Sz) are connected in anti-parallel to six freewheeling diodes (Du, Dv, Dw, Dx, Dy, Dz), respectively. The inverter circuit (13) has a pair of input nodes connected to both ends of the capacitor (C) of the DC link section (12), and converts the DC output by the converter circuit (11) into AC by the switching operation of switching elements (Su, Sv, Sw, Sx, Sy, Sz) and supplies the AC to the motor (30).

[0035] <Control Unit> The control unit (40) is configured using a microcomputer and a memory device storing software for controlling the microcomputer. The control unit (40) controls the output (output AC voltage) of the inverter circuit (13) by controlling the switching operation of the inverter circuit (13) so that the rotation speed (ω) of the motor (30) becomes equal to a given command value (hereinafter referred to as the rotation speed command value (ω*)). In this way, the drive of the motor (30) is controlled.

[0036] In order to realize the above control, the control unit (40) includes, as shown in FIG. 1, a first subtraction unit (41), a speed control unit (42), a dq-axis current command calculation unit (43), a second subtraction unit (44), a PI control unit (45), an addition unit (46), a phase conversion unit (47), a coordinate conversion unit (48), a dq-axis current control unit (49), and a PWM calculation unit (50).

[0037] The first subtraction section (41) calculates the deviation between the rotation speed (ω) of the motor (30) and the rotation speed command value (ω*).

[0038] The speed control unit (42) performs, for example, PID (proportional, integral, differential) calculation based on the deviation calculated by the first subtraction unit (41) to generate a command value for an average motor torque (Tm) (hereinafter, referred to as an average torque command value (Tm*)). The average torque command value (Tm*) is output to a dq-axis current command calculation unit (43).

[0039] The dq-axis current command calculation unit (43) calculates the power supply voltage (v in ) (hereafter referred to as the power supply phase (θin)) in ) frequency (for example, 50 Hz) in *|) is generated. in *|) is generated so that when a waveform obtained by extracting and synthesizing a fundamental wave, a third harmonic, and a fifth harmonic based on the fundamental frequency of the voltage of the AC power supply (20) is multiplied by the polarity of the voltage of the AC power supply (20), the waveform has two or more maximum points in a half cycle of the power supply. in *|) is generated so as to have a non-conduction period in which no current flows from the AC power supply (20) to the converter circuit (11). in The waveform in Figure 2 shows an example of the waveform of the power supply current command value (|i *|) in a half cycle of the power supply. in As shown in Figure 2, this power supply current command value (|i in *|), one maximum point appears in each of the first and second halves. in *|) waveform, the power supply current command value (|i in *|) is set to zero. in ) has a non-conduction period, it is possible to reduce the d-axis current and minimize the effective motor current value. In other words, depending on the length of the non-conduction period, it is possible to choose between minimizing the peak motor current or the effective motor current value.

[0040] The power supply current command value (|i in * In order to generate the dq-axis current command (θ |), the dq-axis current command calculation unit (43) of this embodiment calculates various power supply phases (θ in ) are calculated (more specifically, calculated at the time of design) and stored in the memory device in the form of a table or function (hereinafter referred to as a table, etc.). in * |) value is set to the power phase (θ in ) as an argument and reads it.

[0041] The dq-axis current command calculation unit (43) calculates the q-axis current (i q ) command value (hereinafter referred to as the q-axis current command value (i q * The pulsation command value (i p * ) is generated. p * ) is generated using the following equations (1) to (8).

[0042]

[0043]

[0044]

[0045]

[0046]

[0047]

[0048]

[0049]

[0050] In these equations, v in is the power supply voltage, i in is the power supply current, v dc and P are the voltages at the capacitors (C), respectively. invis the output power of the inverter circuit (13), L is the inductance of the reactor (L), and C is the capacitance of the capacitor (C). d is the d-axis current, i q is the q-axis current, T m is the average motor torque, p n indicates the number of motor pole pairs. In these equations, the "(t)" added after each variable indicates that the value of each variable is the value at time t. However, for simplicity, each equation assumes that there is no loss in the converter circuit (11) and the inverter circuit (13).

[0051] For example, equations (1) to (4) are derived from the relationship between the current and voltage in each part of the circuit (see FIG. 1) that constitutes the power conversion device (10). As can be seen from equations (1) to (5), the power supply current (i in ) absolute value (i.e., the power supply current command value (|i in * |)) to inverter power (P inv ) can be derived. inv ) and the motor output (see the right side of equation (6)) are almost equal, so equation (6) holds. m ) can be expressed as in equation (7). As can be seen from equation (7), the d-axis current (i d ) is constant, the average motor torque (T m ) is the q-axis current (i q ) will be proportional to

[0052] Therefore, as shown in equation (8), the q-axis current (i q ) is the inverter power (P inv ) is approximately proportional to the inverter power (P inv ) is normalized so that the average value is 1, and the average torque command value (T m * ) to obtain the q-axis current (i q ) is the command value (i p * ) can be calculated.

[0053] The second subtraction unit (44) calculates the DC voltage (v dc ) command value (V dc_c ) to the DC voltage (v dc ) predicted value (V dc_p ) to obtain the DC voltage (v dc ) command value (V dc_c ) and predicted value (V dc_p The control unit (40) calculates the deviation of this DC voltage (v dc ) predicted value (V dc_p ) into DC voltage (v dc ) is calculated by referring to the detected value of the DC voltage (v dc ) predicted value (V dc_p ) is the reference DC voltage (v dc ) is the value based on the detected value of the DC voltage (v dc ) predicted value (V dc_p ) is the reference DC voltage (v dc ) is a value one control cycle ahead of the timing at which the

[0054] The PI control unit (45) adjusts the compensation amount (q-axis current command compensation amount (i comp * In this example, the PI control unit (45) calculates and outputs the DC voltage (v dc ) command value (V dc_c ) and predicted value (V dc_p ) and then performs, for example, PI (proportional, integral) calculation to obtain the q-axis current command compensation amount (i comp * The second subtraction section (44) and the PI control section (45) form a feedback control section (51).

[0055] The adder (46) calculates the pulsation command value (i p * ) to the q-axis current command compensation amount (i comp * ) and the sum is used as the q-axis current command value (i q * ) to the dq axis current control section (49).

[0056] The phase converter (47) converts the DC link current (i dc) to the u-phase current (i u ) and w-phase current (i w ) and output.

[0057] The coordinate conversion unit (48) converts the u-phase current (i u ) and w-phase current (i w ) and the electrical angle (motor phase) of the rotor (not shown) of the motor (30), a so-called dq transformation is performed to obtain the d-axis current (i d ) and q-axis current (i q ) is derived. Note that the u-phase current (i u ) and v-phase current (i v ) can be directly detected by providing a current sensor, for example.

[0058] The dq-axis current control unit (49) calculates the d-axis current command value (i d *), q-axis current command value (i q *), d-axis current (i d ), and q-axis current (i q ) based on the d-axis voltage command value (v d *) and q-axis voltage command value (v q Specifically, the dq-axis current control unit (49) derives the d-axis current command value (i d *) and d-axis current (i d ) and the q-axis current command value (i q *) and q-axis current (i q ) so that the deviation from the d-axis voltage command value (v d *) and q-axis voltage command value (v q *) is derived.

[0059] The PWM calculation unit (50) generates a control signal (G) for controlling the on / off of the switching elements (Su, Sv, Sw, Sx, Sy, Sz) in the inverter circuit (13). Specifically, the PWM calculation unit (50) generates a control signal (G) for controlling the on / off of the switching elements (Su, Sv, Sw, Sx, Sy, Sz) in the inverter circuit (13). dc ), d-axis voltage command value (v d *), q-axis voltage command value (v qThe PWM calculation unit (50) sets the duty ratio of a control signal (G) to be supplied to each of the switching elements (Su, Sv, Sw, Sx, Sy, Sz) based on the duty ratio (*). When the control signal (G) is output, each of the switching elements (Su, Sv, Sw, Sx, Sy, Sz) performs a switching operation (on / off operation) at the duty ratio set by the PWM calculation unit (50). The control signal (G) is periodically updated to control the switching operation in the inverter circuit (13).

[0060] <Operation of the power conversion device> When the power conversion device (10) starts operating, the converter circuit (11) in ) is full-wave rectified and output to the DC link unit (12). The DC link unit (12) receives the output of the converter circuit (11) as an input and converts it into a power supply voltage (v in ) pulsating at twice the frequency of the dc ) as shown in Figure 3. dc ) is a constant value greater than 0 during a predetermined period near the zero crossing (hereinafter referred to as the zero crossing vicinity period (P0)). During this zero crossing vicinity period (P0), the power supply voltage (v in ) is zero, and the DC voltage (v dc ) is the period corresponding to the valley of the pulsation waveform.

[0061] In the power conversion device (10), the dq-axis current command calculation unit (43) calculates the power supply voltage (v in ) frequency (for example, 50 Hz) of the power supply current command value (|i in The dq-axis current command calculation unit (43) generates the generated power supply current command value (|i in *|), the pulsation command value (i p On the other hand, the PI control unit (45) generates a power supply current command value (|i in *|) and DC voltage (v dc ) command value (V dc_c ) and predicted value (V dc_p ) so that the deviation from the q-axis current command compensation amount (i comp * ) is calculated. As a result, the q-axis current command value (iq *) is calculated.

[0062] In this way, the q-axis current command value (i q *) is calculated, the dq-axis current control unit (49) calculates the d-axis current command value (i d *), q-axis current command value (i q *) etc., the d-axis voltage command value (v d *) and q-axis voltage command value (v q *) is generated. As a result, a control signal (G) is generated by the PWM calculation unit (50), and the inverter circuit (13) performs a switching operation in accordance with the control signal (G). As a result, a predetermined AC power is supplied from the inverter circuit (13) to the motor (30), thereby driving the motor (30).

[0063] As described above, in the first embodiment, the control unit (40) controls the inverter circuit (13) so as to provide a non-conduction period during which no current flows from the AC power supply (20) to the converter circuit (11).

[0064] 4 shows the power supply voltage (v) in the circuit of FIG. 1 under the following conditions: condition 1 in which a current flows from the inverter circuit (13) to the capacitor (C); condition 2 in which a current flows from the capacitor (C) to the inverter circuit (13); and condition 3 in which no current flows between the inverter circuit (13) and the capacitor (C). in ) and DC voltage (vdc). in ) waveform is shown.

[0065] From FIG. 5, under condition 1, the power supply current (i in ) can be most effectively suppressed.

[0066] When the non-conduction period is provided as in the first embodiment, there is a risk of LC resonance occurring at a transition timing (t1) (see FIG. 6 ) when the non-conduction period transitions to a conduction period in which a current flows from the AC power supply (20) to the converter circuit (11). In FIG. 7 , the inverter current (i inv) is a positive value. Therefore, immediately after the transition timing (t1), current flows to the motor (30), and the DC voltage (v dc ) decreases, the energy of the reactor (L) becomes larger than the energy of the capacitor (C), and resonance is likely to occur. Therefore, in the first embodiment, during a half-cycle period (T1) (see FIG. 6) of the LC resonance starting from the transition timing (t1) (see FIG. 6), the inverter current (i inv ) is integrated to be less than or equal to 0. dc ) command value (V dc_c ) to set the DC voltage (v dc ) command value (V dc_c ) is the DC voltage (v dc ) is the power supply voltage (v in ) is set to gradually increase along the absolute value of the inverter current (i inv ) is set to 0 or less, dc ) command value (V dc_c ) to set the

[0067] Furthermore, in the first embodiment, the inverter current (i inv ) is integrated to be less than or equal to 0. dc ) command value (V dc_c ) is set. Note that the inverter current (i inv ) becomes 0 or less, and during part or all of the period (T2), the inverter current (i inv ) may be made to exceed zero.

[0068] Therefore, in the first embodiment, as shown in FIG. in ) and DC voltage (v dc ) and the inverter current (i inv) is equal to or less than 0. Also, during the half-cycle period (T2) of the LC resonance immediately before the transition timing (t1), the inverter current (i inv ) is 0 or less. This reduces the power supply current (i in ) harmonics can be suppressed. Also, at the transition timing (t1), inv ) is set to 0 or less, so the inverter current (i inv ) exceeds 0, the power supply current (i in ) harmonics can be suppressed. This also makes it possible to reduce the size of the reactor (L).

[0069] In addition, in the first embodiment, the DC voltage (v dc ) command value (V dc_c ) is further set so that the amplitude of the current flowing through the reactor (L) is attenuated by more than 80% during the resonance suppression period. Therefore, the control unit (40) operates the inverter circuit (13) to attenuate the amplitude of the current flowing through the reactor (L) by more than 80% during the resonance suppression period of three cycles of the LC resonance starting from the transition timing (t1). In other words, at the end of the resonance suppression period, the amplitude of the current flowing through the reactor (L) is less than 20% of that at the transition timing (t1). Ｌ The amplitude of the rising edge of the current is A, the damping coefficient is B, and the resonance frequency is f ＬＣ Then, the current I Ｌ is expressed by the following formula:

[0070] I Ｌ = Ae －Ｂｔ sin(2πf ＬＣ t) Figure 8 shows the current I when the damping coefficient is 1000. Ｌ As shown in FIG. 9, the waveform of the current I Ｌis attenuated by a predetermined attenuation ratio C% for each resonance period. Fig. 10 shows the relationship between the attenuation ratio C when the resonance frequency is 1950 Hz and the ratio of harmonics to harmonics when the attenuation ratio C is 0 at the end of the resonance suppression period (a period of three periods of the LC resonance starting from the transition timing (t1)). By setting the attenuation ratio C to 40% or more, the harmonics can be reduced to 10% or less of the harmonics when the attenuation ratio C is 0. The change in the ratio of harmonics to the attenuation ratio C is large until the attenuation ratio C reaches 40%, and decreases when the attenuation ratio C is 40% or more. Therefore, it is preferable to set the attenuation ratio C to 40% or more. Furthermore, in Fig. 9, when the attenuation ratio C for each resonance period is 40%, the current I Ｌ At the end of the resonance suppression period, the amplitude of the current I is reduced by approximately 80% compared to the first half cycle from the transition timing (t1). Therefore, by setting the attenuation ratio C to 40% or more, the amplitude of the current I Ｌ The amplitude of the signal can be reduced by 80% or more.

[0071] Therefore, in the first embodiment, the amplitude of the current flowing through the reactor (L) is attenuated by more than 80% during the resonance suppression period, so that the power supply current (i in ) harmonics can be suppressed.

[0072] Second Embodiment Fig. 11 shows the configuration of a power conversion device (10) according to a second embodiment of the present disclosure. In the second embodiment, the control unit (40) includes a repetitive control unit (52) instead of the PI control unit (45).

[0073] As shown in FIG. 12, the repetitive control unit (52) has a first index generation unit (521), a power supply phase calculation unit (522), a second index generation unit (523), a third subtraction unit (524), a first switching unit (525), a deviation storage unit (526), ​​a second switching unit (527), and a compensation amount calculation unit (528).

[0074] The first index generating unit (521) outputs a switching signal (SW1) that specifies which of K phase ranges the current power supply phase (θin) falls into.

[0075] The power supply phase calculation unit (522) calculates the current power supply phase (θin).

[0076] The second index generating unit (523) calculates the compensation amount to be calculated this time based on the current power supply phase (θin) calculated by the power supply phase calculating unit (522). dc ) detection value. Specifically, the second index generation unit (523) calculates the power supply phase (θin) that is 3 / 4 of the pulse width modulation period ahead of the current power supply phase (θin). Then, the second index generation unit (523) outputs a switching signal (SW2) that specifies to which of K phase ranges the calculated power supply phase (θin) belongs.

[0077] The third subtraction unit (524) subtracts the DC voltage (v dc ) from the detected value of DC voltage (v dc ) command value (V dc_c ) to obtain the DC voltage (v dc ) command value (V dc_c ) and DC voltage (v dc ) and calculate the deviation from the detected value.

[0078] The first switch unit (525) selects one of the input terminals of the deviation storage unit (526) in response to the switch signal (SW1) output by the first index generation unit (521), and then connects the selected input terminal to the output of the third subtraction unit (524).

[0079] The deviation storage unit (526) divides the power supply phase (θin) of 0 to 180° into phase ranges of 0° or more and less than 180° / K, 180° / K or more and less than 360° / K, 360° / K or more and less than 540° / K, ..., 180°*(K-1) / K or more and less than 180°, and assigns indexes of 1 to K in order to each phase range. Also, the deviation input from the first switching unit (525) is stored as the deviation of the phase range specified by the switching signal (SW1).

[0080] The second switching unit (527) outputs to the compensation amount calculation unit (528) the deviation corresponding to the phase range specified by the switching signal (SW2) output by the second index generation unit (523) from among the deviations stored in the deviation memory unit (526).

[0081] The compensation amount calculation unit (528) calculates the compensation amount (q-axis current command compensation amount (i comp * The compensation amount calculation unit (528) calculates and outputs the q-axis current command compensation amount (i comp * ) is required.

[0082] In the second embodiment, as in the first embodiment, the DC voltage (v dc ) command value (V dc_c ) is set.

[0083] The other configurations are the same as those in the first embodiment, so the same components are denoted by the same reference numerals and detailed description thereof will be omitted.

[0084] 13 shows the configuration of a power conversion device (10) according to a third embodiment of the present disclosure. In the third embodiment, an adder (46) calculates the sum of a value obtained by multiplying a q-axis current command compensation amount output by a feedback (FB) control unit (51) by −1 and a value obtained by multiplying a q-axis current command compensation amount output by a repetitive control unit (52) by −1 as a pulsation command value (i p * ) is added.

[0085] The other configurations are the same as those in the first embodiment, so the same components are denoted by the same reference numerals and detailed description thereof will be omitted.

[0086] FIG. 14 shows the DC voltage (v dc ), DC voltage command value (V dc_c ), power supply voltage (v in ), DC voltage (v dc ) and the compensation amount generated by feedback control of the DC voltage (v dc ) is generated by the repetitive control of the power supply current (i in ), power supply current command value (|i in *|), inverter current (i inv ), and q-axis current (i q ) is shown.

[0087] As shown in FIG. 14, the DC voltage (v dc ) repetitive control does not cause a control delay, so the DC voltage (v dc ) and power supply voltage (v in ) become equal to each other, the compensation amount generated by the repetitive control becomes less than 0. Therefore, as shown in FIG. 15, at the transition time (t1), the inverter current (i inv ) can be made 0 or less, and the power supply current (i in ) can reduce the current flowing to the motor (30).

[0088] Fourth Embodiment FIG. 16 illustrates a configuration of a power conversion device (10) according to a fourth embodiment of the present disclosure. In the fourth embodiment, a resonance suppression circuit (14) serving as a resonance suppression unit is connected in parallel with a capacitor (C). The resonance suppression circuit (14) includes a resonance suppression circuit switching element (141), a resistor (142), and a capacitance element (capacitor) (143), which are connected in series in this order from the input node side of the upper arm of the inverter circuit (13). A diode (144) is connected in parallel with the resonance suppression circuit switching element (141) with its cathode facing the capacitance element (143). A fan motor inverter circuit (145) serving as a second inverter circuit is connected to the capacitance element (143). The fan motor inverter circuit (145) converts the voltage of the capacitance element (143) into AC and supplies the AC voltage to a fan motor (60) serving as a second load different from the motor (30). The fan motor inverter circuit (145) includes at least one switching element (145a).

[0089] The control section (40) determines the transition timing (t1) to be the timing when the voltage of the capacitive element (143) is higher than the voltage of the capacitor (C).

[0090] The control unit (40) controls the switching element (141) for the resonance suppression circuit so that the integral value of the current flowing from the capacitor (C) to the resonance suppression circuit (14) becomes 0 or less during the half-cycle period of the LC resonance starting from the transition timing (t1).

[0091] Furthermore, at the transition timing (t1), the control section (40) controls the switching element (141) for the resonance suppression circuit so that the current flowing from the capacitor (C) to the resonance suppression circuit (14) becomes zero or less.

[0092] In addition, the control unit (40) operates the switching element (141) for the resonance suppression circuit to attenuate the amplitude of the current flowing through the reactor (L) by more than 80% during the resonance suppression period of three cycles of the LC resonance starting from the transition timing (t1).

[0093] The other configurations are the same as those in the first embodiment, so the same components are denoted by the same reference numerals and detailed description thereof will be omitted.

[0094] As shown in FIG. 17 , the voltage of the resonance suppression circuit (14) is maintained at or above the voltage of the capacitor (C). Therefore, by turning on the resonance suppression circuit switching element (141), a current can flow from the capacitance element (143) to the capacitor (C). The diode (144) prevents a current from flowing out of the capacitance element (143) and a voltage drop across the capacitance element (143) when the resonance suppression circuit switching element (141) is turned off. Furthermore, when the resonance suppression circuit switching element (141) is turned off, the capacitance element (143) can be charged via the diode (144).

[0095] Furthermore, since the diode (144) is provided, when the switching element (141) for the resonance suppression circuit is turned off, the control unit (40) controls the fan motor inverter circuit (145) to supply power to the fan motor (60), thereby reducing the voltage of the capacitance element (143) and the DC voltage (v dc ) (the voltage of the capacitor (C)) can be adjusted to be lower. Therefore, during the period from the time when half a resonance period has passed since the transition timing (t1) to the time when one resonance period has passed since the transition timing (t1), the DC voltage (v dc ) is the power supply voltage (v in ) when the DC voltage (v dc ) to reduce the power supply voltage (v in ) and DC voltage (v dc) and the resonance can be reduced by controlling the inverter circuit (145) for the fan motor. dc ) and reduce resonance. dc ) can also be reduced by controlling the inverter circuit (13).

[0096] Fifth Embodiment Fig. 18 shows the configuration of a power converter (10) according to a fifth embodiment of the present disclosure. In the fifth embodiment, the AC power supply (20) is a three-phase AC power supply.

[0097] The maximum power consumption of the motor (30) is Pmax (W), and the voltage value of the AC power supply (20) is V. ｉｎ When Pmax≧2000 holds, the following equation (9) holds:

[0098]

[0099] The transition timing (t1) is the timing of transition from a non-conduction period in which current of a predetermined phase among the three phases does not flow from the AC power source (20) to the converter circuit (11) to a conduction period in which current of the predetermined phase flows from the AC power source (20) to the converter circuit (11).

[0100] The other configurations are the same as those in the first embodiment, so the same components are denoted by the same reference numerals and detailed description thereof will be omitted.

[0101] In the second to fourth embodiments, the AC power supply (20) may be a three-phase AC power supply, as in the fifth embodiment.

[0102] Although the first load is the compressor motor (30) in the first to fifth embodiments, it may be another load. Furthermore, although the second load is the fan motor (60) in the fourth embodiment, it may be another load as long as it is different from the first load.

[0103] Furthermore, in the first to fifth embodiments, the reactor (L) is connected between the AC power supply (20) and the converter circuit (11), but it may be connected between the converter circuit (11) and the inverter circuit (13).

[0104] In the first to fifth embodiments, the control unit (40) operates at least one of the inverter circuit (13), the resonance suppression circuit switching element (141), and the fan motor inverter circuit (145) to attenuate the amplitude of the current flowing through the reactor (L) by more than 80% during the resonance suppression period. However, a physical quantity other than the current flowing through the reactor (L) that correlates with the pulsation of the magnetic energy of the reactor (L) due to LC resonance may also be attenuated by more than 80%.

[0105] Although the embodiments have been described above, it will be understood that various modifications of form and details are possible without departing from the spirit and scope of the claims. Furthermore, the above embodiments and modifications may be combined or substituted as appropriate as long as the functionality of the subject matter of the present disclosure is not impaired.

[0106] The present disclosure is useful as a power conversion device that converts power output from an AC power supply and supplies the converted power to a load.

[0107] DESCRIPTION OF SYMBOLS 10 Power conversion device 11 Converter circuit (rectifier circuit) 13 Inverter circuit (first inverter circuit, resonance suppression unit) 14 Resonance suppression circuit (resonance suppression unit) 141 Switching element for resonance suppression circuit 143 Capacitance element 144 Diode 145 Inverter circuit for fan motor (second inverter circuit) 145a Switching element 20 AC power supply 30 Motor (first load) 40 Control unit 60 Fan motor (second load) Su, Sv, Sw, Sx, Sy, Sz Switching element C Capacitor (DC link capacitor) L Reactor t1 Transition timing T1 Period v ｄｃ DC voltage

Claims

1. A rectifier circuit (11) that rectifies and outputs an AC current output from a single-phase AC power source (20); a first inverter circuit (13) having a plurality of switching elements (Su, Sv, Sw, Sx, Sy, Sz) and converting a DC current output from the rectifier circuit (11) into an AC current by switching operations of the switching elements (Su, Sv, Sw, Sx, Sy, Sz) and supplying the AC current to a first load (30); a DC link capacitor (C) that is connected between input nodes of the first inverter circuit (13) and has a capacitance value set to allow fluctuations in the output voltage of the rectifier circuit (11) and suppress ripple voltage caused by the switching operations; a reactor (L) that is connected between the rectifier circuit (11) and the first inverter circuit (13) or between the AC power source (20) and the rectifier circuit (11); and a control unit (40) that controls the first inverter circuit (13) so as to have a non-conduction period in which no current flows from the AC power supply (20) to the rectifier circuit (11), the power conversion device further comprising a resonance suppression unit (13, 14) that is connected in parallel with the DC link capacitor (C) and has at least one switching element (Su, Sv, Sw, Sx, Sy, Sz, 141) and suppresses LC resonance of a circuit including the DC link capacitor (C) and the reactor (L), the control unit (40) controls the resonance suppression unit (13, 14) so ​​that an integral value of a current flowing from the DC link capacitor (C) to the resonance suppression unit (13, 14) becomes 0 or less during a half-cycle period (T1) of the LC resonance, the half-cycle period starting from a transition timing (t1) at which the non-conduction period transitions to a conduction period in which a current flows from the AC power supply (20) to the rectifier circuit (11).

2. The power conversion device according to claim 1, wherein the control unit (40) controls the resonance suppression unit (13, 14) so ​​that the current flowing from the DC link capacitor (C) to the resonance suppression unit (13, 14) is equal to or less than 0 at the transition timing (t1).

3. A power conversion device according to claim 1 or 2, characterized in that the resonance suppression section (13, 14) is the first inverter circuit (13), and the first load (30) is a motor (30).

4. The power converter according to claim 3, wherein the motor (30) is a motor (30) for a compressor.

5. A power conversion device as claimed in claim 1 or 2, further comprising a resonance suppression circuit (14) having a capacitance element (143) and a switching element (141) for a resonance suppression circuit connected in series with each other and connected in parallel with the DC link capacitor (C), wherein the resonance suppression section (13, 14) is the resonance suppression circuit (14), and the control section (40) sets the transition timing (t1) to the timing when the voltage of the capacitance element (143) is higher than the voltage of the DC link capacitor (C).

6. A power conversion device according to claim 5, characterized in that the resonance suppression circuit (14) further comprises a diode (144) connected in parallel with the switching element (141) for the resonance suppression circuit with its cathode facing the capacitive element (143).

7. A power conversion device according to claim 5 or 6, characterized in that a second inverter circuit (145) is connected to the capacitive element (143) for converting the voltage of the capacitive element (143) into AC and supplying the AC voltage to a second load (60) different from the first load (30).

8. The power conversion device according to any one of claims 1 to 4, wherein the control unit (40) controls the voltage (v dc a resonance suppression unit (13, 14) that controls the resonance suppression unit (13, 14) based on a detected value of the resonance suppression unit (13, 14).

9. A rectifier circuit (11) that rectifies and outputs AC output from a single-phase AC power source; an inverter circuit (13) having a plurality of switching elements (Su, Sv, Sw, Sx, Sy, Sz) and converting the DC output from the rectifier circuit (11) into AC by switching operations of the switching elements (Su, Sv, Sw, Sx, Sy, Sz) and supplying the AC to a load (30); a DC link capacitor (C) connected between input nodes of the inverter circuit (13) and having a capacitance value set to tolerate fluctuations in the output voltage of the rectifier circuit (11) and suppress ripple voltage caused by the switching operations; a reactor (L) connected between the rectifier circuit (11) and the inverter circuit (13) or between the AC power source (20) and the rectifier circuit (11); and a control unit (40) that controls the inverter circuit (13) to have a non-conduction period in which no current flows from the AC power supply (20) to the rectifier circuit (11), the power conversion device further comprising a resonance suppression unit (13, 14) that is connected in parallel with the DC link capacitor (C), has at least one switching element (Su, Sv, Sw, Sx, Sy, Sz, 141, 145a), and suppresses LC resonance of a circuit including the DC link capacitor (C) and the reactor (L), wherein the control unit (40) operates the resonance suppression unit (13, 14) to attenuate a physical quantity correlated to pulsation of magnetic energy of the reactor (L) caused by the LC resonance by more than 80% during a resonance suppression period of three periods of the LC resonance starting from a transition timing (t1) at which the non-conduction period transitions to a conduction period in which current flows from the AC power supply (20) to the rectifier circuit (11).

10. A rectifier circuit (11) that rectifies and outputs an AC current output from a three-phase AC power source (20); an inverter circuit (13) having a plurality of switching elements (Su, Sv, Sw, Sx, Sy, Sz) and converting the DC current output by the rectifier circuit (11) into an AC current by switching operations of the switching elements (Su, Sv, Sw, Sx, Sy, Sz) and supplying the AC current to a load; a DC link capacitor (C) that is connected between input nodes of the inverter circuit (13) and has a capacitance value set to allow fluctuations in the output voltage of the rectifier circuit (11) and suppress ripple voltage caused by the switching operations; a reactor (L) that is connected between the rectifier circuit (11) and the inverter circuit (13) or between the AC power source (20) and the rectifier circuit (11); a control unit (40) that controls the inverter circuit (13) so that a non-conducting period occurs during which a current of a predetermined phase among the three phases does not flow from the AC power supply (20) to the rectifier circuit (11), the power conversion device further comprising a resonance suppression unit (13, 14) that is connected in parallel with the DC link capacitor (C), has at least one switching element (Su, Sv, Sw, Sx, Sy, Sz, 141, 145a), and suppresses LC resonance of a circuit including the DC link capacitor (C) and the reactor (L), the control unit (40) operates the resonance suppression unit (13, 14) to attenuate a physical quantity correlated to pulsation of magnetic energy of the reactor (L) caused by the LC resonance by more than 80% during a resonance suppression period of three periods of the LC resonance starting from a transition timing (t1) at which the non-conduction period transitions to a conduction period in which a current of the specified phase flows from the AC power supply (20) to the rectifier circuit (11).

11. A power conversion device according to claim 9 or 10, characterized in that the physical quantity is the amplitude of a current flowing through the reactor (L) during the resonance suppression period.

12. A rectifier circuit (11) that rectifies and outputs an AC current output from a three-phase AC power source (20); an inverter circuit (13) having a plurality of switching elements (Su, Sv, Sw, Sx, Sy, Sz) and converting a DC current output by the rectifier circuit (11) into an AC current by switching operations of the switching elements (Su, Sv, Sw, Sx, Sy, Sz) and supplying the AC current to a load (30); a DC link capacitor (C) that is connected between input nodes of the inverter circuit (13) and has a capacitance value set to allow fluctuations in the output voltage of the rectifier circuit (11) and suppress ripple voltage caused by the switching operations; a reactor (L) that is connected between the rectifier circuit (11) and the inverter circuit (13) or between the AC power source (20) and the rectifier circuit (11); a control unit (40) that controls the inverter circuit (13) so that a non-conduction period is provided in which a current of a predetermined phase among the three phases does not flow from the AC power source (20) to the rectifier circuit (11), the power conversion device further comprising a resonance suppression unit (13, 14) that is connected in parallel with the DC link capacitor (C) and has at least one switching element (Su, Sv, Sw, Sx, Sy, Sz, 141) and suppresses LC resonance of a circuit including the DC link capacitor (C) and the reactor (L), the control unit (40) controls the resonance suppression unit (13, 14) so ​​that an integral value of a current flowing from the DC link capacitor (C) to the resonance suppression unit (13, 14) becomes equal to or less than 0 during a half cycle of the LC resonance starting from a transition timing (t1) at which the non-conduction period transitions to a conduction period in which a current of the predetermined phase flows from the AC power source (20) to the rectifier circuit (11).

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