Power conversion equipment and refrigeration cycle application equipment

Abstract

The power conversion device (100) includes current detection units (5a, 5b) that detect a converter current flowing in and out of a three-phase PWM converter (50), a voltage detection unit (6) that detects a converter voltage applied to the three-phase PWM converter (50) or a power supply voltage output from a three-phase power supply (110), a reactor (2) that suppresses a change in the converter current, a noise filter (1) that suppresses the outflow of a noise current generated by the three-phase PWM converter (50), and a control unit (14) that controls the converter current so that distortion of the power supply current flowing in and out of the three-phase power supply (110) complies with a harmonic standard, wherein a core (401) of the reactor (2) is made of an electromagnetic steel sheet, and a response frequency of a controller that controls the converter current is set to be equal to or less than half the minimum frequency of a plurality of resonant frequencies in a power supply resonance that occurs depending on the relationship between the impedances of the three-phase power supply (110), the noise filter (1), and the reactor (2).

Description

[Technical Field]

[0001] The present disclosure relates to a power conversion device and refrigeration cycle application equipment equipped with a pulse width modulation (PWM) converter that converts alternating current (AC) power supplied from an alternating current (AC) power source into direct current (DC) power and supplies the DC power to a load. [Background technology]

[0002] The power supply current flowing in and out of an AC power supply contains harmonic currents called power supply harmonics. Power supply harmonics are frequency components with frequencies higher than the fundamental frequency. To suppress interference caused by harmonic currents, international regulations have been established for electronic devices that generate power supply harmonics. To comply with these regulations, power conversion devices used in air conditioners and other appliances often employ a configuration equipped with a PWM converter that suppresses harmonic currents contained in the power supply current by chopping the AC current. In addition, in this type of power conversion device, a noise filter is often inserted between the AC power supply and the PWM converter to prevent noise.

[0003] Patent Document 1 below discloses a power conversion device equipped with a three-phase PWM converter. The use of any PWM converter, not limited to a three-phase PWM converter, makes it easier to suppress power supply harmonics because the power supply current is controlled to a sinusoidal waveform. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-151755 Summary of the Invention [Problem to be solved by the invention]

[0005] In a configuration equipped with a noise filter and a PWM converter, a resonance phenomenon may occur due to the impedance relationship between the AC power supply, noise filter, and AC reactor. This resonance phenomenon is also called "power supply resonance." In a power conversion device, if the power supply resonance interferes with the control response of the PWM converter, the PWM converter control amplifies the resonant frequency component. If the degree of interference with the power supply resonance is large, the control of the PWM converter may become unstable, and in the worst case, the control of the PWM converter may fail. Furthermore, if the degree of interference with the power supply resonance is large, the distortion of the power supply current may increase, potentially failing to meet power supply harmonic specifications.

[0006] The present disclosure has been made in view of the above, and has an object to provide a power conversion device that can ensure the stability of control of a PWM converter and suppress power supply harmonics at the same time. [Means for solving the problem]

[0007] In order to solve the above-mentioned problems and achieve the object, a power conversion device according to the present disclosure is a power conversion device equipped with a three-phase PWM converter that converts AC power supplied from an AC power source into DC power and supplies it to a load, and includes a current detection unit, a voltage detection unit, an AC reactor, a noise filter, and a control unit, as described below. The current detection unit detects the converter current flowing in and out of the PWM converter, and the voltage detection unit detects the converter voltage applied to the PWM converter or the power supply voltage output by the AC power source. The AC reactor suppresses the amount of change in the converter current, and the noise filter suppresses the outflow of noise current generated by the PWM converter. The control unit controls the converter current so that distortion of the power supply current flowing in and out of the AC power source complies with harmonic standards. .Ko Controlling the inverter current Control unit The response frequency is set to be equal to or less than half the minimum frequency of a plurality of resonance frequencies in the power supply resonance that occurs depending on the relationship between the impedances of the AC power supply, the noise filter, and the AC reactor. [Effects of the Invention]

[0008] The power conversion device according to the present disclosure has the effect of ensuring the stability of the control of the PWM converter and suppressing power supply harmonics at the same time. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a diagram showing a configuration example of a power conversion device according to a first embodiment; [Figure 2] FIG. 1 is a diagram showing a detailed configuration example of a power conversion device according to a first embodiment; [Figure 3] FIG. 1 is a diagram showing an example of an equivalent circuit when the power conversion device according to the first embodiment is connected to a three-phase power supply; [Figure 4] FIG. 10 is a diagram illustrating the relationship between the resonance frequency of the power supply resonance generated in the power conversion device according to the first embodiment and the response frequency and frequency range of the carrier frequency set in the power conversion device. [Figure 5] FIG. 1 is a diagram schematically illustrating a structure of a reactor used in a power conversion device according to a first embodiment. [Figure 6] FIG. 1 is a diagram showing an example of a control system configured in a control unit according to the first embodiment; [Figure 7] FIG. 1 is a block diagram showing an example of a hardware configuration for realizing the functions of a control unit according to a first embodiment. [Figure 8] FIG. 10 is a diagram showing a configuration example of an air conditioner according to a second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, a power conversion device and a refrigeration cycle applied device according to embodiments of the present disclosure will be described in detail with reference to the accompanying drawings.

[0011] Embodiment 1 1 is a diagram showing an example of the configuration of a power conversion device 100 according to embodiment 1. The power conversion device 100 according to embodiment 1 is a power conversion device that converts AC power supplied from a three-phase power supply 110, which is a three-phase AC power supply, into DC power and outputs the DC power to a load 130. The power conversion device 100 includes a three-phase PWM converter 50, a noise filter 1 that suppresses the outflow of a noise current generated by the three-phase PWM converter 50, and a reactor 2 that is an AC reactor that suppresses the amount of change in the converter current flowing in and out of the three-phase PWM converter 50.

[0012] 1 shows a case where the AC power supply is a three-phase, three-wire type, but the AC power supply may be a three-phase, four-wire type, a single-phase, three-wire type, or a single-phase, two-wire type. When the AC power supply is a single-phase, three-wire type or a single-phase, two-wire type, the three-phase PWM converter 50 is replaced with a single-phase PWM converter, and the noise filter 1 and the reactor 2 are also replaced with ones having structures suited to the AC power supply.

[0013] 2 is a diagram illustrating a detailed configuration example of the power conversion device 100 according to the first embodiment. The power conversion device 100 according to the first embodiment is configured to convert an AC voltage output from a three-phase power supply 110 into a DC voltage and apply the DC voltage to a load 130. As illustrated, the phases of the three-phase power supply 110 are represented by R, S, and T, and are referred to as the "R phase," the "S phase," and the "T phase," respectively.

[0014] The load 130 is a DC load that operates on a DC voltage. Although not shown in Fig. 2, the load 130 includes a motor that drives an electric device, an inverter that supplies driving power to the motor, a current detector that detects the current flowing through the inverter or the motor, and a control unit that controls the operation of the inverter.

[0015] The power conversion device 100 according to the first embodiment includes current detection units 5a and 5b, a voltage detection unit 6, and a control unit 14 in addition to the noise filter 1, the reactor 2, and the three-phase PWM converter 50 described in FIG.

[0016] The noise filter 1 is disposed between the three-phase power supply 110 and the reactor 2. The noise filter 1 operates to reduce noise current generated by the three-phase PWM converter 50. The reactor 2 is disposed between the noise filter 1 and the three-phase PWM converter 50. The reactor 2 is a device including a circuit element that temporarily stores electrical energy supplied from the three-phase power supply 110. The reactor 2 operates to suppress the amount of change in the converter current flowing through the three-phase PWM converter 50.

[0017] The current detectors 5a and 5b detect the converter currents flowing in and out of the three-phase PWM converter 50 and output the detected converter current values ​​to the control unit 14. An example of the current detectors 5a and 5b is an ACCT (Alternating Current Transformer). While FIG. 2 illustrates an example in which the current detector 5a detects the R-phase converter current Ir and the current detector 5b detects the T-phase converter current It, the present invention is not limited to this example. It is sufficient for the current detectors 5a and 5b to detect the converter currents of any two of the three phases; the converter currents of the remaining phases can be calculated by utilizing the fact that the currents of the phases are three-phase balanced. In the example of FIG. 2, the S-phase converter current Is is calculated using the R-phase converter current Ir and the T-phase converter current It.

[0018] The voltage detection unit 6 detects the R-phase converter voltage Vr, the S-phase converter voltage Vs, and the T-phase converter voltage Vt applied to the three-phase PWM converter 50, and outputs these detected values ​​to the control unit 14. Note that in FIG. 2, the voltage detection unit 6 detects the phase voltages between the noise filter 1, the reactor 2, and the three-phase PWM converter 50, but it may also detect the power supply voltage output by the three-phase power supply 110.

[0019] The three-phase PWM converter 50 includes a converter main circuit 3, a drive circuit 16, a capacitor 4, a shunt resistor 7 for current detection, a current detection unit 10, and a voltage detection unit 11.

[0020] The converter main circuit 3 converts the AC voltage output from the three-phase power supply 110 into a DC voltage and outputs it to DC buses 19a and 19b. The DC buses 19a and 19b are electrical wiring that connect the converter main circuit 3 to the load 130. The voltage between the DC buses 19a and 19b is called the "bus voltage."

[0021] The output voltage of the converter main circuit 3 is applied across the capacitor 4. The capacitor 4 is connected to the DC buses 19a and 19b. Therefore, in the configuration of FIG. 2, the capacitor voltage across the capacitor 4 is equal to the bus voltage. The capacitor 4 smoothes the output voltage of the converter main circuit 3. The voltage smoothed by the capacitor 4 is applied to the load 130.

[0022] The voltage detection unit 11 detects the bus voltage Vdc and outputs the detected value of the bus voltage Vdc to the control unit 14. A converter current flows through the shunt resistor 7. The current detection unit 10 converts the voltage value generated when the converter current flows through the shunt resistor 7 into a current value and outputs the current value to the control unit 14.

[0023] The converter main circuit 3 includes six switching elements Q1 to Q6 that are connected in a three-phase bridge configuration. The switching elements Q1 and Q2 are connected in series in this order, and a connection point 3a between the switching elements Q1 and Q2 is electrically connected to the R phase of the three-phase power supply 110. The switching elements Q3 and Q4 are connected in series in this order, and a connection point 3b between the switching elements Q3 and Q4 is electrically connected to the S phase of the three-phase power supply 110. The switching elements Q5 and Q6 are connected in series in this order, and a connection point 3c between the switching elements Q5 and Q6 is electrically connected to the T phase of the three-phase power supply 110.

[0024] The switching elements Q1 to Q6 include diodes D1 to D6 connected in parallel, respectively. The diodes D1 to D6 are connected so that their anodes are located on the AC side and their cathodes are located on the DC side. While FIG. 2 shows a case where the switching elements Q1 to Q6 are IGBTs (Insulated Gate Bipolar Transistors), MOSFETs (Metal Oxide Semiconductor Field Effect Transistors) may be used instead of IGBTs. Note that, in the case of MOSFETs, a parasitic diode is built in due to their structure, so a configuration in which the diodes D1 to D6 are not connected in parallel may also be employed.

[0025] The control unit 14 generates control signals S1 to S6 that control the power supply current to a sinusoidal waveform, the bus voltage to a desired voltage, and the converter current so that the distortion of the power supply current complies with the harmonic standards, based on the detection values ​​of the current detection units 5a and 5b, the detection value of the voltage detection unit 6, the detection value of the current detection unit 10, and the detection value of the voltage detection unit 11. The control signals S1 to S6 are PWM signals for controlling the switching elements Q1 to Q6 of the converter main circuit 3, respectively. The PWM signals are generated using a voltage command and a carrier signal. In this document, the repetition frequency of the carrier signal is referred to as the "carrier frequency." The control signals S1 to S6 generated by the control unit 14 are input to the drive circuit 16. Note that the control unit 14 is provided external to the three-phase PWM converter 50, but may also be provided internally to the three-phase PWM converter 50.

[0026] The drive circuit 16 generates drive pulses G1 to G6 based on the control signals S1 to S6. The switching elements Q1 to Q6 of the converter main circuit 3 perform switching operations in response to the drive pulses G1 to G6.

[0027] 3 is a diagram showing an example of an equivalent circuit when the power conversion device 100 according to the first embodiment is connected to a three-phase power supply 110. The equivalent circuit of the power conversion device 100 is composed of a converter output voltage source 250, an impedance Zr of the reactor 2, an impedance Zn of the noise filter 1, and an impedance Zg of the three-phase power supply 110. The converter output voltage source 250 means that the converter output voltage output from the three-phase PWM converter 50 to the three-phase power supply 110 side contains an AC component due to the switching of the converter main circuit 3. In the noise filter 1, a capacitance component of the X capacitor provided in the noise filter 1 and an inductance component of the common mode choke coil provided in the noise filter 1 appear. Note that the self-inductance component of the common mode choke coil is canceled out, so the inductance component appearing in the equivalent circuit is the leakage inductance component of the common mode choke coil.

[0028] 4 is a diagram illustrating the relationship between the resonance frequency of the power supply resonance occurring in the power conversion device 100 according to the first embodiment and the response frequency and frequency range of the carrier frequency set in the power conversion device 100. The response frequency is a frequency set in the controller of the control unit 14 that controls the converter current.

[0029] An example of the frequency characteristics of the power supply current is shown in Fig. 4. The horizontal axis of Fig. 4 represents frequency, and the vertical axis represents gain. As shown in Fig. 3, the equivalent circuit seen from the three-phase PWM converter 50 toward the three-phase power supply 110 has an impedance Zr of the reactor 2, an impedance Zn of the noise filter 1, and an impedance Zg of the three-phase power supply 110. Therefore, the frequency characteristics of the power supply current have two resonance points and one anti-resonance point, as shown in Fig. 4.

[0030] Note that the frequency characteristics shown in Figure 4 are just an example, and depending on the configuration of the noise filter 1, three or more resonance points may appear. Taking this into consideration, in this paper, the resonance frequency, which is the frequency of the lowest resonance point among the multiple resonance points, is referred to as "f min " and the higher resonance frequency among multiple resonance points is "fmax " That is, the resonant frequency f min is the minimum frequency among the multiple resonant frequencies, and the resonant frequency f max is the maximum frequency among the multiple resonant frequencies. In the example of Figure 4, the lower of the two resonant frequencies is the resonant frequency f min The higher of the two resonance points is the resonance frequency f max If the frequency characteristics of the power supply current have three or more resonant frequencies, the resonant frequency that is not the minimum or maximum frequency is the resonant frequency f min and the resonant frequency f max appears between.

[0031] 4 also shows three preferred frequency ranges 1 to 3 for the response frequency and carrier frequency set in the power conversion device 100. Frequency range 1 is a range in which the frequency is equal to or less than f1, frequency range 2 is a range in which the frequency is equal to or greater than f2 and equal to or less than f3, and frequency range 3 is a range in which the frequency is equal to or greater than f4. As shown in FIG. 4, these f1 to f4 are expressed as f1=f min / 2, f2=2f min , f3=f max / 2, f4=2f max That is, frequency range 1 is a range equal to or less than half the minimum frequency of the plurality of resonant frequencies, frequency range 2 is a range equal to or more than twice the minimum frequency and equal to or less than half the maximum frequency of the plurality of resonant frequencies, and frequency range 3 is a range equal to or more than twice the maximum frequency of the plurality of resonant frequencies.

[0032] Furthermore, the frequency characteristics in Figure 4 are an example when there are two resonance points. In the example of Figure 4, if the smaller of the two resonance frequencies is set as the first resonance frequency and the larger of the two resonance frequencies is set as the second resonance frequency, frequency range 2 is a range that is more than twice the minimum frequency and less than half the maximum frequency.

[0033] In the first embodiment, the response frequency of the controller that controls the converter current is set to frequency range 1. By setting it in this way, it is possible to prevent the control response of the PWM converter from interfering with the power supply resonance. The upper limit value f1 of frequency range 1 is set as f1=f min / 2 is just one example, but if the upper limit of frequency range 1 is set to such a value, it is possible to reliably prevent the control response of three-phase PWM converter 50 from interfering with power supply resonance.

[0034] Furthermore, in the example of Fig. 4, the carrier frequency is set to frequency range 2 or frequency range 3 to avoid interference with the power supply resonance and to avoid interference with the response frequency of the controller. However, if there are three or more resonance points, frequency range 2 is set to at least one of two or more ranges that avoid one or more resonance frequencies between the minimum frequency and the maximum frequency and the ranges before and after each of the three or more resonance frequencies including the minimum and maximum frequencies. By setting it in this way, it is possible to prevent oscillation of the power supply current due to interference between the carrier frequency and power supply resonance.

[0035] It is not preferable to set the carrier frequency within frequency range 1. Setting the carrier frequency within frequency range 1 results in the minimum frequency in the frequency characteristics of the power supply current being greater than the carrier frequency. In this case, the inductance of reactor 2 and noise filter 1 must be reduced, which will result in deterioration of power supply harmonics. For this reason, it is preferable to set the carrier frequency within frequency range 2 or frequency range 3, avoiding frequency range 1.

[0036] From the above, the relationship between the response frequency of the controller and the carrier frequency is "response frequency < carrier frequency." Also, the relationship between the first resonant frequency and the carrier frequency is "first resonant frequency < carrier frequency."

[0037] 5 is a diagram schematically illustrating the structure of reactor 2 used in power conversion apparatus 100 according to the first embodiment. As shown in FIG. 5, reactor 2 has three-leg core 401, which may have an EE core, an EI core, or the like shape. Reactor 2 has a shell-type structure in which winding 402 is arranged on the central leg and core 401 surrounds winding 402.

[0038] Furthermore, the material of the core 401 is an electromagnetic steel sheet. By using an electromagnetic steel sheet for the core 401, it is possible to increase the inductance component of the reactor 2 while suppressing an increase in the size of the reactor 2. If the inductance component of the reactor 2 can be increased, it is possible to obtain the effect of making it easier to suppress power supply harmonics.

[0039] 6 is a diagram illustrating an example of a control system 140 configured in the control unit 14 according to embodiment 1. As shown in FIG. 6, the control system 140 includes a phase correction unit 141, a three-phase / pq conversion unit 142, a voltage / current control unit 143, a pq / three-phase conversion unit 144, and a PWM signal generation unit 145.

[0040] Converter voltages Vr, Vs, Vt and converter currents Ir, Is, It are input to the phase correction unit 141. The phase correction unit 141 compensates for the phase of at least one of the converter voltages Vr, Vs, Vt and the converter currents Ir, Is, It so that the phase difference between each phase of the converter voltages Vr, Vs, Vt and the converter currents Ir, Is, It becomes zero.

[0041] A three-phase / pq conversion unit 142 performs pq conversion on the phase-compensated converter voltages Vr, Vs, Vt and converter currents Ir, Is, It to calculate voltage values ​​Vpq and current values ​​Ipq in the pq coordinate system. A voltage / current control unit 143 generates a voltage command Vpq_ref in the pq coordinate system using the phase-compensated voltage values ​​Vpq and current values ​​Ipq. The response frequency described above is a frequency set in a controller that realizes the voltage / current control unit 143.

[0042] A pq / three-phase conversion unit 144 converts the voltage command Vpq_ref in the pq coordinate system into a voltage command Vrst_ref in the three-phase coordinate system. A PWM signal generation unit 145 generates a PWM signal based on the voltage command Vrst_ref and a carrier signal having a set carrier frequency.

[0043] The control system 140 described above is characterized in that it performs phase compensation on the converter voltages Vr, Vs, and Vt, which are the detection values ​​of the voltage detection unit 6, and the converter currents Ir, Is, and It, which are determined from the detection values ​​of the current detection units 5a and 5b, using a phase correction unit 141. By providing the control system 140 with the phase correction unit 141, the power factor of the input power to the three-phase PWM converter 50 is controlled to be 1, thereby achieving the effect of improving the efficiency of the power conversion device 100.

[0044] At the end of the first embodiment, a description will be given of a hardware configuration for realizing the functions of the above-described control unit 14. Fig. 7 is a block diagram showing an example of a hardware configuration for realizing the functions of the control unit 14 according to the first embodiment.

[0045] To realize some or all of the functions of the control unit 14 described above, the configuration may include a processor 201 that performs calculations and a memory 202 that stores programs read by the processor 201, as shown in FIG. 7.

[0046] The processor 201 is an example of a computing means. The processor 201 may be a computing means called a microprocessor, a microcomputer, a CPU (Central Processing Unit), or a DSP (Digital Signal Processor). Examples of the memory 202 include non-volatile or volatile semiconductor memories such as RAM (Random Access Memory), ROM (Read Only Memory), flash memory, EPROM (Erasable Programmable ROM), and EEPROM (registered trademark) (Electrically EPROM), as well as magnetic disks, flexible disks, optical disks, compact disks, minidisks, and DVDs (Digital Versatile Discs).

[0047] The memory 202 holds a program that executes the functions of the control unit 14. The processor 201 receives and transmits necessary information and stores it in the memory 202, and the processor 201 executes the program held in the memory 202 and refers to the data and tables stored in the memory 202, thereby executing the above-mentioned processing. The calculation results by the processor 201 can be stored in the memory 202.

[0048] The memory 202 holds a program that executes the functions of the control unit 14. The processor 201 receives and transmits necessary information via an interface including an analog-digital converter and a digital-analog converter (not shown), stores the information in the memory 202, and executes the program stored in the memory 202 and refers to the data stored in the memory 202, thereby executing the above-mentioned processing. The calculation results by the processor 201 can be stored in the memory 202.

[0049] As described above, the power conversion device according to the first embodiment is a power conversion device including a three-phase PWM converter that converts AC power supplied from an AC power source into DC power and supplies the DC power to a load, and includes a current detection unit, a voltage detection unit, an AC reactor, a noise filter, and a control unit, as described below. The current detection unit detects the converter current flowing in and out of the PWM converter, and the voltage detection unit detects the converter voltage applied to the PWM converter or the power supply voltage output from the AC power source. The AC reactor suppresses changes in the converter current, and the noise filter suppresses the outflow of noise current generated by the PWM converter. The control unit controls the converter current so that distortion of the power supply current flowing in and out of the AC power source complies with harmonic standards. The core of the AC reactor is made of electromagnetic steel sheet, and the response frequency of the controller that controls the converter current is set to less than half the smallest frequency of multiple resonant frequencies in the power supply resonance that occurs depending on the relationship between the impedances of the AC power source, the noise filter, and the AC reactor. According to the power conversion device of the first embodiment, the response frequency of the controller is set to half or less the minimum frequency of the plurality of resonant frequencies. Therefore, the carrier frequency when avoiding interference with the power supply resonance and the response frequency is set to have a sufficient frequency difference from the response frequency. This makes it possible to prevent the response frequency of the controller from interfering with the carrier frequency. Furthermore, since the inductance of the AC reactor is related to the resonant frequency of the power supply resonance, when the frequency is set to avoid interference between the power supply resonance and the carrier frequency, the minimum frequency of the plurality of resonant frequencies is smaller than the carrier frequency, thereby ensuring the inductance of the AC reactor. Therefore, by using the power conversion device of the first embodiment, it is possible to ensure both stable control of the PWM converter and suppression of power supply harmonics.

[0050] In the power conversion device according to the first embodiment, the carrier frequency may be set to a range of at least twice the maximum frequency of the plurality of resonant frequencies. By setting the carrier frequency in this manner, the carrier frequency is set to have a sufficient frequency difference from the response frequency, making it possible to prevent the response frequency of the controller from interfering with the carrier frequency.

[0051] Furthermore, in the power conversion device according to the first embodiment, when the number of the multiple resonant frequencies is two, the smaller of the two resonant frequencies is the first resonant frequency, and the larger of the two resonant frequencies is the second resonant frequency, the carrier frequency may be set in a range of at least twice the first resonant frequency and not more than half the second resonant frequency, or at least twice the second resonant frequency. By setting the carrier frequency to at least twice the second resonant frequency, the carrier frequency is set with a sufficient frequency difference from the response frequency, making it possible to prevent the response frequency of the controller from interfering with the carrier frequency. Furthermore, by setting the carrier frequency within a range of at least twice the first resonant frequency and not more than half the second resonant frequency, the degree of freedom in selecting the carrier frequency can be increased.

[0052] Furthermore, in the power conversion device according to the first embodiment, the control unit may include a phase correction unit that corrects the phase of at least one of the converter current and the converter voltage so that the phase difference between the converter current and the converter voltage becomes 0. By including such a phase correction unit, the power factor of the input power to the PWM converter is controlled to become 1, thereby improving the efficiency of the power conversion device.

[0053] Embodiment 2 8 is a diagram showing an example of the configuration of an air conditioner 300 according to embodiment 2. The air conditioner 300 according to embodiment 2 is an example of refrigeration cycle equipment, and includes a motor drive device 150 equipped with the power conversion device 100 according to embodiment 1. The air conditioner 300 also includes a compressor 81, a four-way valve 82, an outdoor heat exchanger 83, an expansion valve 84, an indoor heat exchanger 85, and refrigerant piping 86. In the air conditioner 300, a refrigeration cycle is configured by circulating a refrigerant through the compressor 81, the four-way valve 82, the outdoor heat exchanger 83, the expansion valve 84, the indoor heat exchanger 85, and the refrigerant piping 86.

[0054] The air conditioner 300 may be a separate type air conditioner in which the outdoor unit is separated from the indoor unit, or an integrated type air conditioner in which the compressor 81, indoor heat exchanger 85, and outdoor heat exchanger 83 are provided in a single housing.

[0055] A compression mechanism 87 that compresses the refrigerant and a motor 120 that operates the compression mechanism 87 are provided inside the compressor 81. The motor 120 is driven by a motor drive device 150. The motor drive device 150 converts AC power supplied from a three-phase power supply 110 into drive power for the motor 120, thereby driving the motor 120.

[0056] The components of the air conditioner 300 can also be applied to appliances such as refrigerators or freezers equipped with a refrigeration cycle. In addition, in the second embodiment, the motor 120 is used as the drive source for the compressor 81, but the motor 120 may also be used as the drive source for driving an indoor unit blower and an outdoor unit blower (not shown) instead of the compressor 81. In addition, the motor 120 may be used as the drive source for each of the indoor unit blower, the outdoor unit blower, and the compressor 81, and these three motors 120 may be driven by the motor drive device 150.

[0057] The air conditioner 300 according to the second embodiment is configured to include the power conversion device 100 according to the first embodiment, and therefore can ensure the stability of the control of the PWM converter and suppress power supply harmonics, while improving the efficiency of the power conversion device 100. This makes it possible to provide a product that is highly reliable and has high operating efficiency.

[0058] The configurations shown in the above embodiments are merely examples, and may be combined with other known technologies, and parts of the configurations may be omitted or modified without departing from the spirit of the invention. [Explanation of symbols]

[0059] 1 noise filter, 2 reactor, 3 converter main circuit, 3a, 3b, 3c connection point, 4 capacitor, 5a, 5b, 10 current detection unit, 6, 11 voltage detection unit, 7 shunt resistor, 14 control unit, 16 drive circuit, 19a, 19b DC bus, 50 three-phase PWM converter, 81 compressor, 82 four-way valve, 83 outdoor heat exchanger, 84 expansion valve, 85 indoor heat exchanger, 86 refrigerant piping, 87 compression mechanism, 100 power conversion device, 110 three-phase power supply, 120 motor, 130 load, 140 control system, 141 phase correction unit, 142 three-phase / pq conversion unit, 143 voltage / current control unit, 144 pq / three-phase conversion unit, 145 PWM signal generation unit, 150 motor drive device, 201 processor, 202 memory, 250 Converter output voltage source, 300 air conditioner, 401 core, 402 winding, D1, D2, D3, D4, D5, D6 diodes, Q1, Q2, Q3, Q4, Q5, Q6 switching elements.

Claims

1. A power conversion device including a pulse width modulation converter that converts AC power supplied from an AC power source into DC power and supplies the DC power to a load, a current detection unit that detects a converter current flowing in and out of the pulse width modulation converter; a voltage detection unit that detects a converter voltage applied to the pulse width modulation converter or a power supply voltage output from an AC power supply; an AC reactor that suppresses a change in the converter current; a noise filter for suppressing the outflow of noise current generated by the pulse width modulation converter; a control unit that controls the converter current so that distortion of the power supply current flowing in and out of the AC power supply complies with harmonic standards, a response frequency of the control unit is set to be equal to or less than half of a minimum frequency of a plurality of resonant frequencies in a power supply resonance that occurs in accordance with a relationship between impedances of the AC power supply, the noise filter, and the AC reactor;

2. The core of the AC reactor is made of electromagnetic steel sheet. The power conversion device according to claim 1 .

3. a carrier frequency for controlling the switching element of the pulse width modulation converter is set to a range of at least twice the maximum frequency of the plurality of resonant frequencies; The power conversion device according to claim 1 .

4. When the number of the plurality of resonant frequencies is two, the smaller of the two resonant frequencies is defined as a first resonant frequency, and the larger of the two resonant frequencies is defined as a second resonant frequency, a carrier frequency for controlling the switching element of the pulse width modulation converter is set to a range of twice or more of the first resonant frequency and half or less of the second resonant frequency, or to twice or more of the second resonant frequency; The power conversion device according to claim 1 .

5. the control unit includes a phase correction unit that corrects the phases of the converter current and the converter voltage, the phase correction unit compensates for the phase of at least one of the converter current and the converter voltage so that a phase difference between the converter current and the converter voltage becomes zero. The power conversion device according to claim 1 .

6. A refrigeration cycle device comprising the power conversion device according to any one of claims 1 to 5.

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