Converter device and method for controlling same

Abstract

This converter device comprises: a rectifier circuit that converts AC power supplied from an AC power supply into DC power, a power factor correction circuit that is provided with a switching element and is provided on the output side of the rectifier circuit, and a converter control unit (10) that controls the switching element. A converter control unit (10) comprises a voltage command generation unit (21) that generates a voltage command obtained by inverting a negative-side waveform in a sinusoidal voltage waveform, a correction unit (22) that increases the value of the voltage command in a predetermined phase range including at least a phase of 0° and a predetermined phase range including at least a phase of 180°, and a control signal generation unit (24) that generates a control signal for controlling the switching element on the basis of the result of comparison between a corrected voltage command and a carrier wave.

Description

Converter device and control method thereof

[0001] The present disclosure relates to a converter device and a control method thereof.

[0002] Conventionally, converter devices equipped with power factor correction circuits have been proposed (see, for example, Patent Document 1). The power factor correction circuit includes, for example, a reactor, a switching element, and a capacitor, and controls the input current by turning on and off the switching element so as to match the phase with the input voltage, thereby improving the power factor. Specifically, the absolute value of a sinusoidal voltage command is compared with a high-frequency carrier wave (generally a triangular wave), and a rectangular pulse (PWM signal) having an on period in a region where the absolute value of the voltage command is equal to or greater than the carrier wave is generated, and the on / off of the switching element is controlled based on this rectangular pulse.

[0003] Patent No. 6151034

[0004] However, the above-described conventional power factor correction circuit has a problem in that the accuracy of power factor correction decreases in a low load region where the output power is small.

[0005] The present disclosure has been made in view of the above circumstances, and aims to provide a converter device and a control method thereof that can improve the accuracy of power factor correction in a low load region.

[0006] A converter device according to one aspect of the present disclosure includes a rectifier circuit that converts AC power supplied from an AC power source into DC power, a power factor correction circuit that includes a switching element and is provided on the output side of the rectifier circuit, and a control unit that controls the switching element, wherein the control unit includes voltage command generation means that generates a voltage command inverting a negative side waveform in a sinusoidal voltage waveform, correction means that increases the value of the voltage command in a predetermined phase range that includes at least a phase of 0° and a predetermined phase range that includes at least a phase of 180°, and control signal generation means that generates a control signal to control the switching element based on a comparison result between the corrected voltage command and a carrier wave.

[0007] A control method for a converter device according to one aspect of the present disclosure is a control method for a converter device that includes a rectifier circuit that converts AC power supplied from an AC power source into DC power, and a power factor correction circuit that includes a switching element and is provided on the output side of the rectifier circuit, wherein the control method for a converter device includes a computer executing the following processes: generating a voltage command by inverting the negative side waveform of a sinusoidal voltage waveform; increasing the value of the voltage command in a predetermined phase range that includes at least a phase of 0° and a predetermined phase range that includes at least a phase of 180°; and generating a control signal for controlling the switching element based on a comparison result between the corrected voltage command and a carrier wave.

[0008] According to the converter device and the control method thereof of the present disclosure, it is possible to improve the accuracy of power factor correction in the low load region.

[0009] FIG. 1 is a diagram showing a schematic configuration of a motor drive device according to an embodiment of the present disclosure. FIG. 2 is a diagram showing an example of a hardware configuration of a converter control unit according to an embodiment of the present disclosure. FIG. 3 is a functional configuration diagram showing an example of functions provided in the converter control unit according to an embodiment of the present disclosure. FIG. 4 is a diagram showing an example of correction information according to an embodiment of the present disclosure. FIG. 5 is a diagram for explaining the on / off of switching elements and the flow of input current in a converter device according to an embodiment of the present disclosure. FIG. 6 is a diagram for explaining the operation of a converter control unit according to an embodiment of the present disclosure. FIG. 7 is a diagram showing an example of a simulation result of an input current waveform of a converter device according to an embodiment of the present disclosure. FIG. 8 is a diagram showing a relationship between output power and relative error in a conventional converter device. FIG. 9 is a diagram showing a comparison between the relationship between output power and relative error of a converter device according to an embodiment of the present disclosure and the relationship between output power and relative error of a conventional converter device. FIG. 10 is a diagram showing a comparison between the relationship between output power and relative error when the carrier frequency of the carrier wave is set to 6 kHz, 3 kHz, and 2.5 kHz in a converter device according to an embodiment of the present disclosure, and the relationship between output power and relative error when the carrier frequency of the carrier wave is set to 6 kHz in a conventional converter device. 1 is a diagram showing a comparison of the relative error of a conventional method when the output power is 300 [W] with the relative error when the carrier frequency of the carrier wave is set to 6 kHz, 3 kHz, and 2.5 kHz in a converter device according to an embodiment of the present disclosure.

[0023] FIG. 1 is a diagram showing a comparison of the relationship between the inverter efficiency [%] when the carrier frequency of the carrier wave is set to 6 kHz, 3 kHz, and 2.5 kHz in a converter device according to an embodiment of the present disclosure, and the inverter efficiency when the carrier frequency of the carrier wave is set to 6 kHz in a conventional converter device.

[0024] FIG. 1 is a diagram showing a comparison of the inverter efficiency of a conventional method when the output power is 300 [W] with the inverter efficiency when the carrier frequency of the carrier wave is set to 6 kHz, 3 kHz, and 2.5 kHz in a converter device according to an embodiment of the present disclosure.

[0025] FIG. 1 is a diagram showing an example configuration of an air conditioner to which a motor drive device according to an embodiment of the present disclosure is applied.

[0010] A converter device and a control method thereof according to an embodiment of the present disclosure will be described below with reference to the drawings. Fig. 1 is a diagram showing a schematic configuration of a motor drive device 1 according to an embodiment of the present disclosure. The motor drive device 1 includes a converter device 20 and an inverter device 30. The converter device 20 converts AC power supplied from an AC power source 4 into DC power and outputs the DC power. The inverter device 30 converts the DC power into three-phase AC power and outputs the DC power to a motor M, which is a load.

[0011] In the present embodiment, a case where single-phase AC power is supplied from the AC power supply 4 to the converter device 20 will be described as an example, but the present invention is not limited to this. For example, three-phase AC power may be supplied from the AC power supply 4. The motor M is driven in response to the three-phase AC power supplied from the inverter device 30. An example of the motor M is a compressor motor used in an air conditioner.

[0012] The converter device 20 includes, for example, a rectifier circuit 3 and a power factor correction circuit 5. The rectifier circuit 3 is, for example, a bridge circuit in which a plurality of diodes are bridge-connected. However, the configuration of the rectifier circuit 3 is not limited to this. The configuration of the rectifier circuit 3 is well known, and various rectifier circuits can be appropriately adopted.

[0013] The power factor correction circuit 5 is provided on the output side of the rectifier circuit 3 and includes a switching element 6. The power factor correction circuit 5 includes, for example, the switching element 6, a capacitor 7, and a reactor (inductive element) 8.

[0014] The capacitor 7 is connected between the DC output terminals of the rectifier circuit 3. The capacitor 7 is, for example, an electrolytic capacitor. The reactor 8 is provided in series with a positive bus Lp that connects the rectifier circuit 3 and the capacitor 7. A diode 9 is connected in series with the current output side of the reactor 8. The switching element 6 has a first terminal connected to the positive bus Lp between the reactor 8 and the diode 9, and a second terminal connected to the negative bus Ln.

[0015] Examples of the switching element 6 include semiconductor switches such as an insulated gate bipolar transistor (IGBT) and a field effect transistor (FET).

[0016] The switching element 6 is controlled by a converter control unit (control unit) 10. The converter control unit 10 will be described in detail later.

[0017] The power factor correction circuit 5 shown in Fig. 1 is an example and is not limited to this. A known power factor correction circuit having a switching element can be appropriately adopted as the power factor correction circuit 5 according to this embodiment. For example, a configuration including a plurality of switching circuits as described in Patent Document 1 or the like may be adopted.

[0018] The AC power supply 4 is provided with a zero-cross detector 17 for detecting zero-cross points. A zero-cross signal from the zero-cross detector 17 is output to the converter control unit 10. Note that, since many known methods have been proposed for detecting zero-cross points, any of these known techniques may be applied as appropriate.

[0019] For example, the zero-cross detector 17 detects the input voltage Vac (power supply voltage) using a voltage sensor and outputs a zero-cross signal according to the polarity of the input voltage Vac. The zero-cross detector 17 may output a signal of "1" during a period when the input voltage Vac is positive and a signal of "0" during a period when the input voltage Vac is negative. This allows the converter control unit 10 to detect the timing at which the zero-cross signal switches as a zero-cross point. The zero-cross signal is not limited to the above. For example, the zero-cross detector 17 may output a signal of "0" during a period when the input voltage Vac is positive and a signal of "1" during a period when the input voltage Vac is negative.

[0020] The inverter device 30 includes, for example, an IPM (Intelligent Power Module) 31 and an inverter control unit 40. The IPM 31 is, for example, a bridge circuit made up of six switching elements.

[0021] Each switching element of the IPM 31 is on / off controlled based on a control signal (e.g., a PWM signal) output from the inverter control unit 40, whereby the DC power supplied from the converter device 20 is converted into three-phase AC power and output to the motor M, which is a three-phase AC motor. Note that the configuration of the inverter device 30 is an example and is not limited to this. For example, a known configuration can be appropriately adopted as the inverter device 30.

[0022] Next, a detailed description will be given of the converter device 20. FIG. 2 is a diagram showing an example of the hardware configuration of the converter control unit 10.

[0023] As shown in FIG. 2, the converter control unit 10 is, for example, a computer such as a microcomputer, and includes a CPU (Central Processing Unit: processor) 11, a main memory 12, a secondary storage 13, etc.

[0024] The main memory device 12 is composed of writable memory such as cache memory and RAM (Random Access Memory), and is used as a working area for reading out programs executed by the CPU 11 and writing data processed by the programs.

[0025] The secondary storage device 13 is a non-transitory computer-readable storage medium. The secondary storage device 13 is, for example, a semiconductor memory. Examples of the secondary storage device 13 include a flash memory and an SSD (Solid State Drive). The secondary storage device 13 stores programs for implementing various processes and various data required for implementing the various processes. A plurality of secondary storage devices 13 may be provided, and the above-mentioned programs and data may be divided and stored in each secondary storage device 13.

[0026] The converter control unit 10 may include a communication interface 15. The communication interface 15 functions as an interface for connecting to a network, communicating with other devices, and transmitting and receiving information. For example, the communication interface 15 communicates with other devices via wired or wireless communication. Examples of wired communication include serial communication such as RS-232C and RS-485, CAN (Controller Area Network), and Ethernet. Examples of wireless communication include communication via lines such as Bluetooth (registered trademark), Wi-Fi, mobile communication systems (3G, 4G, 5G, 6G, LTE, etc.), and wireless LAN.

[0027] For example, converter control unit 10 may be realized by a PLC (Programmable Logic Controller) or the like.

[0028] For example, the converter control unit 10 communicates with the inverter control unit 40 to exchange information, thereby controlling the converter device 20 .

[0029] The inverter control unit 40 has the same configuration as the converter control unit 10 described above, and a detailed description thereof will be omitted. In Fig. 1, the converter control unit 10 and the inverter control unit 40 are shown as separate components, but they may be integrated together or may be realized by the hardware described above.

[0030] A series of processes for realizing the functions of the converter control unit 10 (described later) is stored in the form of a program in the secondary storage device 13, for example, and the CPU (processor) 11 reads this program into the main storage device 12 and executes information processing and arithmetic processing to realize various functions. The program may be pre-installed in the secondary storage device 13, or may be distributed via wired or wireless communication means, for example.

[0031] Fig. 3 is a functional configuration diagram showing an example of functions provided in the converter control unit 10. As shown in Fig. 3, the converter control unit 10 includes a voltage command generation unit 21, a correction unit 22, a carrier wave generation unit 23, and a control signal generation unit 24.

[0032] The voltage command generator 21 generates a voltage command Sa by inverting the negative side waveform of a sinusoidal voltage waveform.

[0033] For example, the voltage command generator 21 generates a sinusoidal voltage waveform based on the zero-cross signal from the zero-cross detector 17, a pre-registered converter control phase (phase difference from the power supply voltage), and the voltage command amplitude value, and inverts the negative side waveform of the generated voltage waveform to generate the voltage command Sa (see FIG. 6 ). As an example, the voltage command Sa is expressed by |sin θ|. Note that the method for generating the voltage command is not limited to the above, and any known method can be used as appropriate.

[0034] The corrector 22 corrects the voltage command Sa by increasing the value of the voltage command Sa in a predetermined phase range that includes at least a phase of 0° and a predetermined phase range that includes at least a phase of 180°.

[0035] The predetermined phase range including at least a phase of 0° includes, for example, a period of 0≦θ≦45°, preferably a phase period of 0°≦θ≦65°, and more preferably a period of 0°≦θ<90°.

[0036] The predetermined phase range including at least a phase of 180° includes, for example, a period of 180≦θ≦225°, preferably includes a phase period of 180°≦θ≦245°, and more preferably includes a period of 180°≦θ<270°.

[0037] For example, the corrector 22 corrects the voltage command Sa using a correction value, where the correction value is set to a larger value as the current value of the input current Iin decreases.

[0038] Specifically, the corrector 22 corrects the voltage command Sa using a first correction value α to be added to the voltage command Sa and a second correction value β to be multiplied by the voltage command Sa.

[0039] In other words, the corrector 22 corrects the voltage command Sa using the correction formula expressed by the following formula (1).

[0040] Sb=α+β*|sinθ| (1)

[0041] In the above equation (1), |sin θ| represents the voltage command Sa before correction.

[0042] The first correction value α is set to a value greater than zero and less than 1, and the second correction value β is set to a value greater than zero and less than 1 (0≦α<1, 0<β≦1). The smaller the current value of the input current Iin, the larger the first correction value α is set to, and the smaller the current value of the input current Iin, the smaller the second correction value β is set to.

[0043] Preferably, the first correction value α and the second correction value β are set so that the sum of the first correction value α and the second correction value β becomes 1. That is, the first correction value α and the second correction value β are set in advance so as to satisfy the following formula (2).

[0044] α + β = 1 (2)

[0045] For example, the correction unit 22 has correction information in which the current value of the input current Iin is associated with a first correction value α and a second correction value β as shown in Fig. 4. Then, the correction unit 22 obtains the first correction value α and the second correction value β corresponding to the current value of the input current Iin from the correction information, and corrects the voltage command Sa by using the obtained first correction value α and second correction value β in the above equation (1).

[0046] The correction information shown in FIG. 4 is created based on the test results obtained by performing simulations or tests using an actual device in advance, for example.

[0047] The carrier wave generating unit 23 generates, for example, a carrier wave (e.g., a triangular wave) Sc of a predetermined carrier frequency (see FIG. 6 ). It is advisable to adopt the lowest possible carrier frequency, taking into consideration various factors, such as harmonic regulation values, noise regulation values, power factor, and switching loss. By lowering the carrier frequency as much as possible, it is possible to reduce switching loss as much as possible. An appropriate carrier frequency can be determined based on the results of preliminary testing using an actual device or simulations.

[0048] Based on the comparison result between the corrected voltage command Sb and the carrier wave Sc, the control signal generating unit 24 generates a control signal Sd for controlling the switching element 6. Specifically, the control signal generating unit 24 compares the corrected voltage command Sb with the carrier wave Sc, and generates, as the control signal Sd, a rectangular pulse (PWM signal) whose on period is a region where the voltage command Sb is equal to or greater than the carrier wave Sc (see FIG. 6 ).

[0049] The control signal Sd is output to a gate driver (not shown) that drives the switching element 6, and the on / off of the switching element 6 is controlled based on this control signal Sd.

[0050] As a result, as shown in FIG. 5, during the on period of the switching element 6, a current flows through the switching element 6, storing energy in the reactor 8, and during the off period of the switching element 6, a current corresponding to the energy stored in the reactor 8 flows through the capacitor 7.

[0051] Figure 6 is a schematic diagram illustrating, for comparison, the control signal Sd when a voltage command Sb corrected using the first correction value α = 0.5 and the second correction value β = 0.5 is used, and the control signal Sd' generated by a conventional method, in other words, the control signal Sd' when a voltage command Sa is used.

[0052] As shown in FIG. 6, the control signal Sd according to this embodiment has a shorter ON period than the control signal Sd' generated by the conventional method.

[0053] Fig. 7 is a diagram showing the simulation results when the switching element 6 is controlled by a control signal Sd' generated using a voltage command Sa when the output power (power supplied to the motor M in Fig. 1) is 150 W, and Fig. 8 is a diagram showing the simulation results when the voltage command Sa is corrected using the formula (1) and the correction information shown in Fig. 4, and the switching element 6 is controlled by a control signal Sd generated using the corrected voltage command Sb when the output power is 130 W. Note that the carrier wave Sc used in the simulations shown in Figs. 7 and 8 has a higher carrier frequency than the carrier wave Sc shown in Fig. 6.

[0054] The input current waveform shown in Fig. 7 shows that an excessive current flows relative to the input voltage Vac in the range of 0°≦θ≦45° (region A), and the current drops to nearly zero around θ=90° (region B). The power factor in Fig. 7 was 73.4%.

[0055] 8 is kept to a relatively small value in the range of 0°≦θ≦45° (region A'), and shows a value approximately equal to the input voltage Vac. Also, even when θ is near 90° (region B'), the current value does not drop to near zero, ensuring a constant amount of current.

[0056] The reason why the input current Iin flows in region B' is that the value of the input current Iin in region A' is suppressed, so the DC bus voltage Vdc (the voltage between the terminals of the capacitor 7) can be kept low (Vdc = 342 V in FIG. 7 and Vdc = 320 V in FIG. 8), and a period occurs in which the input voltage Vac exceeds the DC bus voltage Vdc around θ = 90°, causing the input current Iin to flow.

[0057] As a result, according to the converter device 20 of this embodiment shown in FIG. 8, a power factor of 85.7% can be obtained even in a low load region where the output power is as low as 130 W, and it can be seen that a high power factor improvement effect is obtained compared to the converter device using the conventional method shown in FIG. 7.

[0058] As described above, the converter device 20 and the control method and program thereof according to this embodiment provide the following advantageous effects.

[0059] That is, converter device 20 includes a rectifier circuit 3 that converts AC power supplied from an AC power source 4 into DC power, a switching element 6, a power factor correction circuit 5 provided on the output side of rectifier circuit 3, and a converter control unit 10 that controls the switching element 6. Converter control unit 10 also includes a voltage command generation unit 21 that generates a voltage command Sa (e.g., |sin θ|) obtained by inverting the negative side waveform of a sinusoidal voltage waveform, a correction unit 22 that increases the value of voltage command Sa in a predetermined phase range that includes at least a phase of 0° and a predetermined phase range that includes at least a phase of 180°, and a control signal generation unit 24 that generates a control signal Sd for controlling the switching element 6 based on a comparison result between the corrected voltage command Sb and a carrier wave Sc.

[0060] This makes it possible to shorten the on-period of the switching element 6 compared to the conventional technique in a predetermined phase range including at least a phase of 0° and a predetermined phase range including at least a phase of 180°. As a result, as illustrated in Fig. 8, in a predetermined phase range near the phase of 0° (for example, see region A' in Fig. 8), the value of the input current can be reduced, and the accuracy of power factor correction can be improved.

[0061] Conventionally, one of the reasons for the low accuracy of power factor correction in the low load region is thought to be a decrease in the accuracy of power estimation by a converter control unit (for example, a microcomputer).

[0062] For example, Figure 9 shows the relationship between output power [W] and relative error [%] in a conventional converter device. Here, the relative error [%] is the value obtained by dividing the absolute value of the difference between the actual power [W] and the estimated power [W] calculated by a converter control unit (e.g., a microcomputer) by the actual power [W] and multiplying the result by 100. For example, if the actual power is 100 [W] and the estimated power calculated by the converter control unit is 120 [W], the relative error is 20 [%].

[0063] As shown in Figure 9, in the conventional converter device, the smaller the output power, the larger the relative error. Also, the larger the relative error, the lower the power factor. In other words, Figure 9 shows that there is a correlation between the relative error and the power factor, and that an improved power factor leads to a reduced relative error, and vice versa.

[0064] Here, the conventional converter device (conventional control method) means controlling the switching element 6 using a control signal generated by comparing the voltage command Sa output from the voltage command generating unit 21 with the carrier wave.

[0065] 10 is a graph showing a comparison of the relationship between the output power [W] and the relative error [%] of the converter device 20 of this embodiment and the relationship between the output power [W] and the relative error [%] of a conventional converter device. As shown in FIG. 10, it can be seen that the converter device 20 of this embodiment has an improved relative error compared to the conventional converter device. From this result, it can be easily inferred that there is also a similarly large power factor improvement effect.

[0066] Furthermore, the converter device according to this embodiment can improve the power factor in the low load region, making it possible to set the carrier frequency of the carrier wave lower than in the past, thereby reducing switching loss compared to the past.

[0067] 11 is a graph showing a comparison of the relationship between the output power and the relative error when the carrier frequency of the carrier wave Sc is set to 6 kHz, 3 kHz, and 2.5 kHz, and the relationship between the output power and the relative error when the carrier frequency of the carrier wave Sc is set to 6 kHz in a conventional converter device. Fig. 11 also shows the relative error when the power factor correction circuit is turned off in the range of output power of 300 W or less, i.e., when the switching element is kept open.

[0068] Figure 12 is a graph comparing the relative error of the conventional method when the output power is 300 W with the relative error when the carrier frequency of the carrier wave Sc is set to 6 kHz, 3 kHz, and 2.5 kHz in the converter device 20 of this embodiment.

[0069] As shown in Fig. 11, according to the converter device 20 of this embodiment, in the range of output power 300 W or more, it is possible to reduce the relative error more than conventionally even when the carrier frequency is set to 2.5 kHz to 6 kHz. In particular, as shown in Fig. 12, when the output power is 300 W, the relative error of the converter device 20 of this embodiment is 12% even when the carrier frequency is set to a low 2.5 kHz, compared to the conventional 35%. This shows that high power estimation accuracy is maintained.

[0070] Furthermore, as shown in FIG. 11, even in the region where the output power is 300 [W] or less, the relative error [%] is suppressed compared to the region where the output power is 300 [W] or more, and it can be seen that high power estimation accuracy is maintained.

[0071] As described above, the converter device 20 according to this embodiment can reduce switching loss while maintaining the power factor improvement effect at a certain level or higher.

[0072] Furthermore, by configuring the motor drive device 1 using the converter device 20 according to this embodiment, it is possible to improve the inverter efficiency [%]. The inverter efficiency [%] is an evaluation value that indicates the ratio of the output power output to the motor M to the input power input to the converter device 20.

[0073] 13 is a graph showing a comparison of the inverter efficiency [%] when the carrier frequency of the carrier wave Sc is set to 6 kHz, 3 kHz, and 2.5 kHz in the converter device 20 according to this embodiment with the inverter efficiency [%] when the carrier frequency of the carrier wave Sc is set to 3 kHz in a conventional converter device. In FIG. 13, the horizontal axis represents output power, and the vertical axis represents inverter efficiency.

[0074] FIG. 14 is a diagram showing a comparison of the inverter efficiency [%] of the conventional method when the output power is 300 [W] and the inverter efficiency [%] when the carrier frequency of the carrier wave Sc is set to 6 kHz, 3 kHz, and 2.5 kHz in the converter device 20 of this embodiment.

[0075] 13 and 14, it can be seen that the converter device 20 of this embodiment can achieve higher inverter efficiency than the conventional one in the output power range of approximately 100 W or more and 600 W or less. In particular, it can be seen that in the low load range of output power of 300 W or less, when the carrier frequency of the carrier wave Sc is set to 2.5 kHz or 3 kHz, higher inverter efficiency than the conventional one can be achieved.

[0076] Although the present disclosure has been described above using embodiments, the technical scope of the present disclosure is not limited to the scope described in the above embodiments. Various modifications or improvements can be made to the above embodiments without departing from the gist of the present disclosure, and such modifications or improvements are also included in the technical scope of the present disclosure.

[0077] For example, as shown in Fig. 9, in the range where the output power is high, the relative error is suppressed to a low value even in the conventional case, and it is clear that a high power factor improvement effect can be obtained. Therefore, in such a power range, it is possible to omit the correction by the correction unit 22.

[0078] Therefore, the converter control unit 10 may have a mode switching unit (not shown) that switches between a first mode in which the voltage command Sa is corrected by the correction unit 22 and a second mode in which the voltage command Sa is not corrected by the correction unit 22, and may switch modes depending on the input current Iin.

[0079] For example, the mode switching unit may select the first mode when the value of the input current Iin is equal to or less than a threshold value, and the second mode when the value of the input current Iin is greater than the threshold value. As a result, when the second mode is selected, the control signal Sd′ is generated by comparing the voltage command Sa with the carrier wave Sc, as in the conventional case.

[0080] The timing of mode switching may be based on the motor output (physical quantity of the load) instead of the input current Iin. Regarding the motor output, a value obtained by multiplying the motor rotation speed and torque, or a value obtained by multiplying the motor voltage and motor current, is used as an evaluation value, and the determination is made based on this evaluation value. In this case, the mode switching unit selects the first mode when the evaluation value is equal to or less than a threshold, and selects the second mode when the evaluation value is greater than the threshold. Regarding various information required for determination, such as the motor rotation speed, motor voltage, and motor current, sensors may be provided to detect these information, and the detected values ​​from these sensors may be input directly to the converter control unit 10, or may be obtained from, for example, the inverter control unit 40.

[0081] It is also preferable to provide hysteresis to the threshold value, which makes it possible to avoid frequent switching of the control method.

[0082] [Application Example] The motor drive device 1 according to this embodiment can be applied to, for example, an air conditioner 50. Fig. 15 is a diagram showing an example of the configuration of an air conditioner 50 to which the motor drive device 1 according to this embodiment is applied.

[0083] 15 , an air conditioner 50 includes a refrigerant circuit 51. The refrigerant circuit 51 mainly includes, for example, a compressor 52 that compresses and sends out a refrigerant, a condenser 54, an expansion valve 55, and an evaporator 56. The refrigerant circuit 51 may also include a four-way valve 53 that switches the circulation direction of the refrigerant. The compressor 52 is controlled by a compressor motor MA that is driven by the motor drive device 1 according to this embodiment. The converter device 20 and motor drive device 1 according to this embodiment are not limited to the air conditioner 50, and can be used in a variety of appliances, such as refrigerators and washing machines.

[0084] (Additional Notes) The converter device 20 and the control method thereof described in the above-described embodiment can be understood, for example, as follows.

[0085] A converter device (20) according to a first aspect of the present disclosure includes a rectifier circuit (3) that converts AC power supplied from an AC power source (4) into DC power, a switching element (6), a power factor correction circuit (5) provided on the output side of the rectifier circuit, and a control unit (10) that controls the switching element, and the control unit includes voltage command generation means (21) that generates a voltage command (Sa) by inverting a negative side waveform in a sinusoidal voltage waveform, correction means (22) that increases the value of the voltage command (Sa) in a predetermined phase range that includes at least a phase of 0° and a predetermined phase range that includes at least a phase of 180°, and control signal generation means (24) that generates a control signal (Sd) for controlling the switching element (6) based on a comparison result between the corrected voltage command (Sb) and a carrier wave (Sc).

[0086] According to the converter device, the voltage command is increased in a predetermined phase range including at least a phase of 0° and a predetermined phase range including at least a phase of 180°. This makes it possible to shorten the on-period of the switching element compared to conventional devices. This makes it possible to reduce the value of the input current in the predetermined phase range near the phase of 0° and the predetermined phase range near the phase of 180°, thereby enhancing the power factor correction effect.

[0087] The power factor correction circuit (5) is, for example, a switching type (active type) power factor correction circuit. The power factor correction circuit (5) has, for example, a reactor (8), a switching element (6), and a capacitor (7), and is a circuit that controls the input current to improve the power factor by turning on and off the switching element (6) so as to match the phase with the input voltage.

[0088] In the converter device (20) according to the second aspect of the present disclosure, in the first aspect, the correction means (22) corrects the voltage command (Sa) using a correction value, and the correction value is set to a larger value as the current value of the input current (Iin) becomes smaller.

[0089] According to the above aspect, the smaller the current value of the input current, the larger the current command is corrected to. As a result, the smaller the current value of the input current, the shorter the on-period of the switching element in a predetermined phase range can be. This makes it possible to keep the input current in the predetermined phase range low, thereby enhancing the power factor improvement effect.

[0090] In a converter device (20) according to a third aspect of the present disclosure, in the above-described first aspect, the correction means (22) corrects the voltage command (Sa) using a first correction value (α) to be added to the voltage command (Sa) and a second correction value (β) to be multiplied by the voltage command (Sa), the first correction value (α) and the second correction value (β) are both set to values ​​greater than zero and less than 1, the first correction value (α) is set to a larger value as the current value of the input current (Iin) is smaller, and the second correction value (β) is set to a smaller value as the current value of the input current (Iin) is smaller.

[0091] According to the above aspect, it is possible to gradually increase the command value of the voltage command, which is expected to improve the power factor correction effect.

[0092] In the converter device (20) according to the fourth aspect of the present disclosure, in the third aspect described above, the first correction value (α) and the second correction value (β) are set so that the sum of the first correction value and the second correction value becomes 1 (α + β = 1).

[0093] According to the converter device, the first correction value and the second correction value can be set to appropriate values, and a further improvement in power factor can be expected.

[0094] A converter device (20) according to a fifth aspect of the present disclosure is any one of the first to fourth aspects, wherein the control unit (10) has a mode switching means for switching between a first mode in which the voltage command (Sa) is corrected by the correction means (22) and a second mode in which the voltage command (Sa) is not corrected by the correction means (22), and the mode switching means switches modes based on an input current or a physical quantity of a load connected to the output side of the power factor correction circuit.

[0095] According to the above aspect, it is possible to set an appropriate mode based on the input current or the physical quantity of the load.

[0096] A motor drive device (1) according to a sixth aspect of the present disclosure includes a converter device (20) according to any one of the first to fifth aspects, and an inverter device (30) that converts output power from the converter device (20) into AC power and outputs the AC power.

[0097] An air conditioner (50) according to a seventh aspect of the present disclosure includes the motor drive device (1) according to the sixth aspect.

[0098] A control method for a converter device (20) according to an eighth aspect of the present disclosure is a control method for a converter device including a rectifier circuit (3) that converts AC power supplied from an AC power source (4) into DC power, and a switching element (6), and a power factor correction circuit (5) provided on the output side of the rectifier circuit (3), in which a computer executes the following processes: generating a voltage command (Sa) by inverting the negative side waveform in a sinusoidal voltage waveform; increasing the value of the voltage command (Sa) in a predetermined phase range that includes at least a phase of 0° and a predetermined phase range that includes at least a phase of 180°; and generating a control signal (Sd) for controlling the switching element (6) based on a comparison result between the corrected voltage command (Sb) and a carrier wave (Sc).

[0099] A program according to a ninth aspect of the present disclosure is a program for causing a computer to execute the control method for the converter device (20) according to the eighth aspect.

[0100] DESCRIPTION OF SYMBOLS 1: Motor drive device 3: Rectifier circuit 4: AC power supply 5: Power factor correction circuit 6: Switching element 7: Capacitor 8: Reactor 9: Diode 10: Converter control unit (control unit) 11: CPU 12: Main memory device 13: Secondary memory device 15: Communication interface 17: Zero cross detection unit 20: Converter device 21: Voltage command generation unit (voltage command generation means) 22: Correction unit (correction means) 23: Carrier wave generation unit 24: Control signal generation unit (control signal generation means) 30: Inverter device 40: Inverter control unit 50: Air conditioner 51: Refrigerant circuit 52: Compressor 53: Four-way valve 54: Condenser 55: Expansion valve 56: Evaporator M: Motor MA: Compressor motor

Claims

1. A converter device comprising: a rectifier circuit that converts AC power supplied from an AC power source into DC power; a power factor correction circuit that includes a switching element and is provided on the output side of the rectifier circuit; and a control unit that controls the switching element, wherein the control unit comprises: voltage command generation means that generates a voltage command by inverting the negative side waveform of a sinusoidal voltage waveform; correction means that increases the value of the voltage command in a predetermined phase range that includes at least a phase of 0° and a predetermined phase range that includes at least a phase of 180°; and control signal generation means that generates a control signal to control the switching element based on the result of comparing the corrected voltage command with a carrier wave.

2. The converter device according to claim 1, wherein the correction means corrects the voltage command using a correction value, and the correction value is set to a larger value as the current value of the input current decreases.

3. The converter device according to claim 1, wherein the correction means corrects the voltage command using a first correction value to be added to the voltage command and a second correction value to be multiplied by the voltage command, the first correction value being equal to or greater than zero and less than 1, and the second correction value being greater than zero and equal to or less than 1, the first correction value being set to a larger value as the current value of the input current becomes smaller, and the second correction value being set to a smaller value as the current value of the input current becomes smaller.

4. The converter device according to claim 3, wherein the first correction value and the second correction value are set so that the sum of the first correction value and the second correction value becomes 1.

5. The converter device according to claim 1, wherein the control unit has a mode switching means for switching between a first mode in which the voltage command is corrected by the correction means and a second mode in which the voltage command is not corrected by the correction means, and the mode switching means switches modes based on an input current or a physical quantity of a load connected to the output side of the power factor correction circuit.

6. A motor drive device comprising: a converter device according to any one of claims 1 to 5; and an inverter device that converts output power from the converter device into AC power and outputs the AC power.

7. An air conditioner equipped with the motor drive device according to claim 6.

8. A control method for a converter device comprising a rectifier circuit that converts AC power supplied from an AC power source into DC power, and a power factor correction circuit that includes a switching element and is provided on the output side of the rectifier circuit, wherein a computer executes the following processes: generating a voltage command by inverting the negative side waveform of a sinusoidal voltage waveform; increasing the value of the voltage command in a predetermined phase range that includes at least a phase of 0° and a predetermined phase range that includes at least a phase of 180°; and generating a control signal for controlling the switching element based on the result of comparing the corrected voltage command with a carrier wave.

9. A program for causing a computer to execute the converter device control method according to claim 8.

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