AC / DC converters, rotating machine drives, and refrigeration cycle application equipment

Abstract

The AC / DC converter (2) includes a rectifier circuit (20) having a switching element (215) and rectifying a power supply voltage applied from an AC power supply (1), a capacitor (216) connected to DC buses (9a, 9b) and smoothing an output voltage of the rectifier circuit (20), a reactor (212) arranged closer to the AC power supply (1) than the capacitor (216), and a control unit (6) generating a switching signal for controlling the switching element (215). The control unit (6) generates the switching signal so that harmonic components contained in a power supply current flowing between the AC power supply (1) and the rectifier circuit (20) comply with a harmonic standard value for the power supply current. The switching element (215) performs a switching operation at least once per half cycle of the power supply voltage.

Description

[Technical Field]

[0001] The present disclosure relates to an AC / DC converter that converts AC power into desired DC power, and to a rotating machine drive device and refrigeration cycle equipment that are equipped with the AC / DC converter. [Background technology]

[0002] When obtaining DC voltage from an AC power source, it is common to use a power factor correction circuit. A power factor correction circuit has the functions of controlling the bus voltage at a constant level and controlling the power supply current so as to comply with harmonic standards. A power factor correction circuit and one of its control methods, the "simple switching method" (also called the "partial switching method"), is a method that switches at least once per half cycle of the power supply voltage, which is the voltage of the AC power supply, and has the characteristic of being able to control the bus voltage lower than the peak value of the power supply voltage. However, when the bus voltage is set lower than the peak value of the AC power supply using the simple switching method, the operating circuit switches from a boost chopper to a capacitor-input diode rectifier, which creates the issue of distorting the power supply current.

[0003] To address this issue, the prior art disclosed in Patent Document 1 below determines whether a combination of reactor capacity and switching timing complies with harmonic standards by repeating the design for each load power. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2000-125545 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the conventional technology described in Patent Document 1 is a method of checking whether compliance with harmonic standards can be achieved through repeated trials, which has the problem that the number of trials increases exponentially as the number of pulses increases. Also, with regard to control gain design, there is a problem that it takes a long time to complete the design because there is no clear guideline for quantitative and unique design.

[0006] The present disclosure has been made in consideration of the above, and aims to shorten the time required for design by obtaining an AC-DC conversion device that can comply with harmonic standards without relying on trial-and-error adjustments. [Means for solving the problem]

[0007] In order to solve the above-mentioned problems and achieve the object, an AC / DC converter according to the present disclosure includes a rectifier circuit, a capacitor, a reactor, and a control unit. The rectifier circuit has at least one switching element and rectifies a power supply voltage applied from an AC power supply. The capacitor is connected to a DC bus and smoothes the output voltage of the rectifier circuit. The reactor is arranged closer to the AC power supply than the capacitor. When generating a switching signal to control the switching element arranged closer to the AC power supply than the capacitor, the control unit generates the switching signal so that harmonic components contained in the power supply current flowing between the AC power supply and the rectifier circuit comply with the harmonic standard value for the power supply current. The switching element performs a switching operation at least once per half cycle of the power supply voltage. [Effects of the Invention]

[0008] According to the AC / DC converter of the present disclosure, it is possible to comply with harmonic standards without relying on trial-and-error adjustments, thereby achieving the effect of reducing the time required for design. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a block diagram showing a configuration example of a rotary machine driving device according to a first embodiment; [Figure 2]1 is a circuit diagram showing a configuration example of an AC-DC converter according to a first embodiment; [Figure 3] FIG. 1 is a block diagram showing a configuration example of a control unit according to a first embodiment. [Figure 4] FIG. 1 is a block diagram showing a configuration example of a voltage control unit according to a first embodiment; [Figure 5] FIG. 1 is a block diagram showing a configuration example of a current control unit according to a first embodiment; [Figure 6] A block diagram showing an example of the configuration when a target value filter is introduced into the current control unit shown in Figure 5. [Figure 7] 7 is a block diagram illustrating the transfer function of a current control system in an AC-DC converter including the current control unit shown in FIG. 6. [Figure 8] FIG. 1 is a block diagram showing a configuration example of a switching signal generating unit according to a first embodiment; [Figure 9] FIG. 7 shows an example of the operating waveforms of the power supply voltage, bus voltage, and power supply current when PI control is applied to the current controller shown in FIG. [Figure 10] FIG. 7 shows an example of the operating waveforms of the power supply voltage, bus voltage, and power supply current when PS control is applied to the current controller shown in FIG. [Figure 11] A diagram showing an example of current harmonic characteristics when PS control is applied to the current controller shown in Figure 6. [Figure 12] FIG. 7 is a diagram showing an example of the relationship between the ratio of the sum of harmonic components and the operating power when PS control is applied to the current controller shown in FIG. [Figure 13] FIG. 10 is a diagram showing a configuration example of an AC-DC converter according to a second embodiment; [Figure 14] FIG. 10 is a diagram showing a configuration example of a refrigeration cycle application device according to a third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An AC-DC converter, a rotary machine drive device, and a refrigeration cycle application device according to embodiments of the present disclosure will be described in detail below with reference to the accompanying drawings.

[0011] Embodiment 1 1 is a block diagram showing an example of the configuration of a rotating machine driving device 8 according to embodiment 1. The rotating machine driving device 8 is connected to an AC power source 1 and a load 4 including a motor 41. The rotating machine driving device 8 includes an AC-DC converter 2 and a DC-AC converter 3. When the rotating machine driving device 8 is used in an air conditioner, the load 4 is a compressor or a fan, and the motor 41 is a compressor motor or a fan motor.

[0012] 2 is a circuit diagram showing a configuration example of the AC-DC converter 2 according to the first embodiment. The AC-DC converter 2 according to the first embodiment mainly includes a control unit 6, a rectifier circuit 20, a reactor 212, and a capacitor 216. The AC-DC converter 2 also includes a current detection unit 211 and voltage detection units 217a and 217b as means for detecting voltage or current. In this document, when the voltage detection units 217a and 217b are distinguished from each other without reference numerals, the voltage detection unit 217b will be referred to as a "first voltage detection unit" and the voltage detection unit 217a will be referred to as a "second voltage detection unit."

[0013] The rectifier circuit 20 includes single-phase diode bridge cells 213a and 213b, each of which has four diodes bridge-connected, and a switching element 215 connected in parallel across the single-phase diode bridge cell 213b. The single-phase diode bridge cells 213a and 213b are connected in parallel to each other across the AC power supply 1. The rectifier circuit 20 shown in FIG. 2 is called a "simple switching circuit." The single-phase diode bridge cell 213b and the switching element 215 form a switching cell 225. The switching element 215 performs a switching operation at least once per half cycle of the power supply voltage.

[0014] The capacitor 216 is connected between the DC bus 9a and the DC bus 9b. The reactor 212 is arranged closer to the AC power supply than the capacitor 216. The rectifier circuit 20 receives the power supply voltage applied from the AC power supply 1 via the reactor 212 and rectifies the received power supply voltage. The capacitor 216 smoothes the output voltage of the rectifier circuit 20.

[0015] The voltage detection unit 217b detects the bus voltage, which is the voltage of the DC buses 9a and 9b to which the capacitor 216 is connected. The voltage detection unit 217a detects the power supply voltage. The current detection unit 211 detects the power supply current flowing between the AC power supply 1 and the rectifier circuit 20.

[0016] The control unit 6 receives the detection values ​​of the voltage detection units 217a and 217b and the current detection unit 211. The control unit 6 generates a switching signal for controlling the on / off of the switching element 215 based on the detection values.

[0017] An example of the switching element 215 is an IGBT (Insulated Gate Bipolar Transistor) shown in the figure, but is not limited to an IGBT. Any element capable of switching operation may be used as the switching element 215. Another example of the switching element 215 is a MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor).

[0018] 2 is configured as a closed loop using the detected values ​​of the voltage detection units 217a, 217b and the current detection unit 211, but may be configured as an open loop using a target value, an estimated value, etc. When the AC-DC conversion device 2 is configured as an open loop, it is also possible to control the switching element 215 without using the detected values ​​of the voltage detection units 217a, 217b and the current detection unit 211.

[0019] 3 is a block diagram showing an example configuration of the control unit 6 according to the first embodiment. The control unit 6 includes a voltage control unit 61, a current control unit 62, and a switching signal generation unit 63. The voltage control unit 61 generates a first current command value using a first voltage command value. The current control unit 62 generates a second voltage command value using the first current command value. The switching signal generation unit 63 generates a switching signal using the second voltage command value.

[0020] 4 is a block diagram showing an example of the configuration of voltage control unit 61 according to the first embodiment. Voltage control unit 61 includes a voltage controller 611 and a subtractor 612. Voltage control unit 61 generates a first current command value using a first voltage command value that is a command value for the bus voltage. More specifically, subtractor 612 generates a voltage deviation that is the difference between the first voltage command value and the detected voltage detected by voltage detection unit 217b. Voltage controller 611 generates the first current command value using the voltage deviation output from subtractor 612. Voltage controller 611 can be configured, for example, by a PI (Proportional Integral) controller.

[0021] The transfer function G when the voltage controller 611 is configured as a PI controller AVR(s) can be expressed by the following equation (1).

[0022]

number

[0023] Here, the transfer function G AVR(s) "AVR" in the above is an abbreviation for "Automatic Voltage Regulator." Also, in the above equation (1), K pAVR is the proportional gain and K iAVR is the integral gain and s is the Laplace operator. In a PI controller, the proportional gain K pAVR and integral gain K iAVR can be determined arbitrarily. Note that the proportional gain K pAVR can be set to zero and configured as an I controller, or the integral gain K iAVR may be set to zero and configured as a P controller.

[0024] FIG. 5 is a block diagram showing an example of the configuration of the current control unit 62 according to the first embodiment. The current control unit 62 includes a current controller 621, a subtractor 622, and a multiplier 623. The current control unit 62 generates a second voltage command value using a second current command value obtained by causing the first current command value to follow a sine wave. More specifically, the multiplier 623 multiplies the first current command value by an excitation signal. The excitation signal is a sine wave synchronized with the phase of the power supply voltage. The sine wave is generated based on a voltage phase, which is the phase of the detected voltage detected by the voltage detection unit 217a. The output of the multiplier 623 is input to the subtractor 622 as a second current command value. The subtractor 622 generates a current deviation, which is the difference between the second current command value and the detected current detected by the current detection unit 211. The current controller 621 generates the second voltage command value using the current deviation output from the subtractor 622. The current controller 621 can be configured, for example, by a PS (Proportional Sinusoidal) controller.

[0025] The transfer function G when the current controller 621 is configured as a PS controller ACR(s) can be expressed by the following equation (2).

[0026]

number

[0027] Here, the transfer function G ACR(s) "ACR" in the above is an abbreviation for "Automatic Current Regulator." Also, in the above formula (2), K pACR is the proportional gain and K sACR is the S control gain, and ω n is the angular frequency and s is the Laplace operator. In the PS controller, the proportional gain K pACR , S control gain K sACR and angular frequency ω n can be determined arbitrarily.

[0028] The PS controller is a controller in which an S controller, which is a Laplace transform expression of a sine wave function or a cosine wave function, is inserted in parallel with a P controller. The S controller operates at an angular frequency ω n This controller has improved tracking performance for a sinusoidal input of angular frequency ω n The reason why the tracking performance improves for pulsating inputs can be explained by the internal model principle. The internal model principle states that if the controller's denominator has the same factors as the denominator polynomial of the command value expressed in Laplace transform, the command value can be tracked without deviation. Note that the current controller 621 may be configured as a PIS controller by inserting an I controller in parallel with the PS controller.

[0029] Fig. 6 is a block diagram showing a configuration example in which a target value filter 624 is introduced into the current control unit 62 shown in Fig. 5. Also, Fig. 7 is a block diagram used to explain the transfer function of the current control system 7 in the AC-DC converter 2 including the current control unit 62 shown in Fig. 6.

[0030] In Fig. 6, a target value filter 624 is inserted in the preceding stage of the current control unit 62 shown in Fig. 5. The target value filter 624 is inserted to adjust the response of the transfer function of the current control unit 62 shown in Fig. 5. Specifically, the response of the transfer function of the current control unit 62 is adjusted by ensuring that the zero points of the transfer function of the current control unit 62 are canceled out by the poles of the target value filter 624.

[0031] Here, the closed loop transfer function G in the current control system 7 in FIG. close(s) can be expressed by the following equation (3).

[0032]

number

[0033] In the above formula (3), G c is the transfer function of any controller 72, and G Pis the transfer function of an arbitrary controlled plant 73. If the above equation (3) has zeros, the closed-loop response cannot be determined by poles alone. Therefore, the closed-loop transfer function G close(s) A target value filter 74 having the same pole as the zero point of is inserted in the front stage of the closed loop. Then, the transfer function G F(s) and the closed-loop transfer function G close(s) The desired response is achieved by canceling out the influence of the zero point between the target value filter 74 and the transfer function G'. close(s) can be expressed by the following equation (4).

[0034]

number

[0035] In the above formula (4), G X is an arbitrary transfer function. The transfer function G X is the transfer function G' close(s) The value of the zeroth power of the Laplace operator s in the denominator polynomial of the transfer function G may be used, or it may have any zero point. F(s) The controller response can be adjusted by applying the target value filter 74 having the following formula: Note that a PI controller may also be used as a controller that achieves the same effect as the target value filter 74.

[0036] 8 is a block diagram showing an example of the configuration of switching signal generation unit 63 according to embodiment 1. Switching signal generation unit 63 includes normalizer 630, carrier signal generator 631, and comparator 632. Normalizer 630 normalizes the second voltage command value input to switching signal generation unit 63. Note that if the control gain of current controller 621 that outputs the second voltage command value is designed taking normalization into consideration, normalizer 630 becomes unnecessary.

[0037] The carrier signal generator 631 generates a carrier signal used to generate a switching signal and outputs it to the comparator 632. The carrier signal is a bipolar or unipolar signal having a triangular waveform that operates at an arbitrary frequency. The comparator 632 generates a switching signal based on the output of the scaler 630 and the output of the carrier signal generator 631. More specifically, the comparator 632 compares the output value of the scaler 630 with the output value of the carrier signal generator 631, and if the output value of the scaler 630 is greater than the output value of the carrier signal generator 631, the comparator 632 outputs a signal to turn on the switching element 215. On the other hand, if the output value of the scaler 630 is smaller than the output value of the carrier signal generator 631, the comparator 632 outputs a signal to turn off the switching element 215. Conversely, the configuration may be such that an ON operation signal is generated when the output value of the normalizer 630 is smaller than the output value of the carrier signal generator 631, and an OFF operation signal is generated when the output value of the normalizer 630 is larger than the output value of the carrier signal generator 631.

[0038] Furthermore, the carrier signal generated by carrier signal generator 631 does not have to be triangular wave, and any configuration may be used as long as it is possible to generate a switching signal from the second voltage command value.

[0039] Next, we will explain the points to consider when configuring the switching signal generating unit 63. To suppress switching loss of the switching element 215 in the switching cell 225, it is desirable to reduce the number of switching operations. To reduce the number of switching operations, the switching frequency can be reduced. On the other hand, if the switching frequency is reduced too much, the frequency components of the carrier signal will be included in components up to the 40th order of the fundamental frequency defined by the current harmonics standard.

[0040] Here, the fundamental frequency is the frequency of the power supply voltage, which in Japan is 50 Hz or 60 Hz. The 40th order of 50 Hz is 2 kHz, and the 40th order of 60 Hz is 2.4 kHz. Therefore, when the power supply voltage frequency is 50 Hz, the carrier frequency, which is the frequency of the carrier signal, must be 2 kHz or higher. Also, when the power supply voltage frequency is 60 Hz, the carrier frequency must be 2.4 kHz or higher. This can be expressed mathematically as in the following equation (5).

[0041]

number

[0042] In the above formula (5), f sw is the carrier frequency, and f si is the carrier frequency f sw is the frequency of the sidebands relative to f s is the frequency of the power supply voltage, and n is an integer equal to or greater than 1.

[0043] In the first embodiment, the carrier frequency f sw is the frequency of the sideband f si The components of the harmonic components should be determined so as to satisfy the harmonic standards. Specifically, the components should be determined so as to satisfy the following equation (6).

[0044]

number

[0045] In the above formula (6), N sw is the number of switching times in one cycle of the power supply voltage. sw / f s ) is the frequency of the power supply voltage f s Carrier frequency f sw and the carrier frequency f sw The frequency of the power supply voltage f s Divide by the power supply frequency fs That is, in the first embodiment, the number of switching times N in one cycle of the power supply voltage is sw occurs at least once and the carrier frequency f sw The frequency of the power supply voltage f s The value divided by (f sw / f s ) is determined as follows:

[0046] In the first embodiment, the number of switching times N sw Although the above formula (6) is shown as a constraint on the load 4, it does not need to be satisfied in all operating regions of the load 4. For example, when the load 4 operates in a light load region, the switching operation of the switching element 215 may be stopped, so the above formula (6) does not need to be satisfied.

[0047] Next, the operating characteristics when PS control is applied to the current controller 621 will be clarified by comparing with the conditions when a PI controller is applied to the current controller 621.

[0048] Fig. 9 is a diagram showing example operating waveforms of the power supply voltage, bus voltage, and power supply current when PI control is applied to the current controller 621 shown in Fig. 6. The upper part of Fig. 9 shows waveforms of the absolute values ​​of the bus voltage and power supply voltage. The lower part of Fig. 9 shows waveforms of the detected power supply current, the fundamental wave component of the detected power supply current, and the power supply current command value. The detected power supply current is the detected waveform of the power supply current detected by the current detection unit 211.

[0049] The operating conditions in Figure 9 are those in which the bus voltage is equal to or less than the peak absolute value of the power supply voltage, as shown in the upper part of Figure 9. Under these conditions, the rectifier circuit 20 operates as a capacitor-input diode rectifier circuit rather than as a boost circuit, making it impossible to control the bus voltage. In this case, an excessive value accumulates in the PI control integrator, causing a windup phenomenon, and the detected power supply current cannot follow the power supply current command value.

[0050] In contrast, Fig. 10 is a diagram showing example operating waveforms of the power supply voltage, bus voltage, and power supply current when PS control is applied to the current controller 621 shown in Fig. 6. As with Fig. 9, the upper part of Fig. 10 shows waveforms of the absolute values ​​of the bus voltage and power supply voltage, and the middle part of Fig. 10 shows waveforms of the detected power supply current, the fundamental wave component of the detected power supply current, and the power supply current command value. The lower part of Fig. 10 also shows a switching signal for controlling the switching element 215.

[0051] As shown in the middle part of Figure 10, the fundamental wave component of the detected power supply current is nearly identical to the power supply current command value. This shows that if PS control, which has high tracking performance for sinusoidal input, is applied to current controller 621, the fundamental wave of the detected power supply current can track the power supply current command value even under conditions where the bus voltage is equal to or less than the peak value of the absolute value of the power supply voltage. Note that Figure 10 shows the results for operating conditions where the bus voltage is equal to or less than the peak value of the absolute value of the power supply voltage, but it goes without saying that the fundamental wave of the detected power supply current will track the power supply current command value even under operating conditions where the bus voltage exceeds the peak value of the absolute value of the power supply voltage.

[0052] Fig. 11 is a diagram showing an example of current harmonic characteristics when PS control is applied to the current controller 621 shown in Fig. 6. The current harmonic standard used in Fig. 11 is IEC61000-3-2 Class A. Note that IEC61000-3-2 Class A is an example of a current harmonic standard, and the current harmonic standard is not limited to this standard.

[0053] In Figure 11, the solid lines indicate the standard values ​​for current harmonics from the 2nd to the 40th order specified in IEC 61000-3-2 Class A. Also in Figure 11, the dashed lines indicate the effective values ​​of the 2nd to the 40th harmonic components during rated operation. The harmonic components during rated operation represent the components remaining after subtracting the fundamental component of the power supply current from the power supply current that flows when the AC-DC converter 2 is operated at rated power. In this paper, the 2nd to the 40th harmonics are defined as "low-order harmonics."

[0054] According to Figure 11, the waveforms of the dashed lines are lower than the waveforms of the solid lines for the 2nd to 40th orders. This shows that if PS control, which has high tracking performance for sine wave input, is applied to current controller 621, the low-order harmonics contained in the power supply current will comply with the harmonic standard values ​​for the power supply current. Note that Figure 11 shows the harmonic components during rated operation as an example, but it goes without saying that the effect of PS control on suppressing harmonic components can be obtained even during times other than rated operation.

[0055] Fig. 12 is a diagram showing an example of the relationship between the ratio of the sum of harmonic components and operating power when PS control is applied to current controller 621 shown in Fig. 6. The ratio of the sum of harmonic components here means the ratio of the sum of second-order and higher harmonic components to the fundamental wave of the power supply current.

[0056] It can be seen from Fig. 12 that the proportion of the sum of harmonic components is 10% or more in all operating regions shown in Fig. 12. The fact that the proportion of the sum of harmonic components is 10% or more is specific to the technique of embodiment 1 in which PS control is applied to current controller 621 to control switching element 215. When the operating power is low, the proportion of the sum of harmonic components increases, but the harmonic standard value when the operating power is low also increases, and as shown in Fig. 11, the effective value of the current harmonics does not exceed the harmonic standard value of the power supply current.

[0057] The control method of the first embodiment is characterized in that a current controller 621 is applied to the control unit 6, and PS control, which has high tracking performance for a sine wave input, is further applied to the current controller 621. While the application of PS control to improve tracking performance for a sine wave input is considered to be a relatively common practice, the application of PS control to comply with harmonic standards is considered to be a novel method that has never been used before.

[0058] As described above, the AC-DC converter according to the first embodiment includes a rectifier circuit that rectifies a power supply voltage applied from an AC power supply, a capacitor that smooths the output voltage of the rectifier circuit, and a reactor that is located closer to the AC power supply than the capacitor. The rectifier circuit has at least one switching element that is located closer to the AC power supply than the capacitor. When generating a switching signal for controlling the switching element, the control unit generates the switching signal so that harmonic components contained in a power supply current flowing between the AC power supply and the rectifier circuit comply with the harmonic standard value of the power supply current. The switching element performs switching operation at least once per half cycle of the power supply voltage. The AC-DC converter according to the first embodiment enables compliance with the harmonic standard without relying on a trial-and-error adjustment method that confirms compliance with the harmonic standard through repeated trials. Furthermore, the AC-DC converter according to the first embodiment enables compliance with the harmonic standard while improving the input power factor, even under operating conditions in which the bus voltage exceeds the peak absolute value of the power supply voltage.

[0059] To achieve the above functions, the control unit according to the first embodiment is configured to include a voltage control unit that generates a first current command value using a first voltage command value, which is a command value for the bus voltage; a current control unit that generates a second voltage command value using a second current command value obtained by making the first current command value follow a sine wave; and a switching signal generation unit that generates a switching signal using the second voltage command value. The current control unit has a current controller, and PS control is applied to the current controller. The input stage of the current control unit is also configured to include a filter that controls the zero point of a feedback loop that feeds back the second voltage command value output by the current control unit to the input stage of the second current command value. Using a control unit configured in this manner eliminates the need to repeatedly design a combination of reactor capacity and switching timing for each load power to determine whether it complies with harmonic standards. This eliminates the need for trial-and-error adjustments and shortens the time required for design work and the time required to complete the design.

[0060] It is desirable that the switching signal generator generates a switching signal so that the number of switching operations of the switching element in one cycle of the power supply voltage is at least one and the carrier frequency, which is the frequency of the carrier signal, is equal to or less than the value normalized by the frequency of the power supply voltage. By generating such a switching signal, it is possible to suppress switching loss in the switching cell.

[0061] When the switching element is controlled using the control unit configured as described above, low-order harmonics are superimposed on the power supply current flowing between the AC power supply and the AC-DC converter. The total harmonic components of the power supply current are 10% or more of the fundamental wave of the power supply current.

[0062] Furthermore, when the control system of the AC-DC converter is configured as a closed loop, it is configured to include a current detection unit that detects a power supply current flowing between the AC power supply and the rectifier circuit, a first voltage detection unit that detects a bus voltage, and a second voltage detection unit that detects a power supply voltage. When the control system of the AC-DC converter is configured as a closed loop, the first current command value may be generated using a voltage deviation that is the difference between the first voltage command value and the detected voltage detected by the first voltage detection unit, and the sine wave that excites the first current command value may be generated based on the voltage phase detected by the second voltage detection unit. Furthermore, the second voltage command value may be generated using a current deviation that is the difference between the second current command value and the detected current detected by the current detection unit.

[0063] Embodiment 2 In the first embodiment, a configuration has been described in which PS control is applied to the current controller 621 of the current control unit 62 for the purpose of improving the follow-up performance to a sinusoidal command. In the second embodiment, a configuration will be described in which PIR (Proportional Integral Resonant) control is applied to the current controller 621 of the current control unit 62 for the same purpose.

[0064] Fig. 13 is a diagram showing a configuration example of an AC-DC converter 2 according to embodiment 2. Components having the same or equivalent functions as those in Fig. 2 are denoted by the same reference numerals. Note that descriptions of content that overlaps with embodiment 1 will be omitted as appropriate.

[0065] 13 has a configuration called a full PAM (Pulse Amplitude Modulation) circuit. The rectifier circuit 20 includes a single-phase diode bridge cell 213a, a switching element 215, and a diode 218. In the single-phase diode bridge cell 213a, the switching element 215 performs a switching operation at least once per half cycle of the power supply voltage.

[0066] 2 is disposed between the single-phase diode bridge cell 213a and the diode 218. The switching element 215 is disposed between the single-phase diode bridge cell 213a and the capacitor 216 and is connected in parallel to the single-phase diode bridge cell 213a and the capacitor 216. The current detection unit 211 described in the configuration of FIG. 2 is disposed between the single-phase diode bridge cell 213a and the diode 218.

[0067] 2 and 13, the positions and connection forms of the switching element 215 and the reactor 212 are different, but in both configurations, the switching element 215 and the reactor 212 are arranged closer to the AC power source 1 than the capacitor 216.

[0068] 13, the switching element 215 is shown as an IGBT, but any element capable of switching operation may be used. Furthermore, although the AC-DC converter 2 shown in FIG. 13 is configured as a closed loop, it may also be configured as an open loop. When the AC-DC converter 2 is configured as an open loop, the detection values ​​of the voltage detectors 217a and 217b and the current detector 211 do not need to be used.

[0069] 13 may be used in the first embodiment, and the simple switching circuit of Fig. 2 may be used in the second embodiment. That is, when the AC-DC converter 2 has a step-up function or a step-down function, the rectifier circuit 20 includes at least one switching element, but the control method described in this paper is applicable even if the control method for controlling the switching element is different.

[0070] Next, the transfer function of the PIR controller will be explained. First, the transfer function G PIR(s) can be expressed by the following equation (7).

[0071]

number

[0072] In the above equation (7), K p is the proportional gain, K i is the integral gain, K r is the resonance control gain, ω1 is the angular frequency of the current control response, and ω2 is the angular frequency of the sine wave command to be followed. Such a transfer function G PIR(s) A PIR controller having the above formula may be applied to the current controller 621 in Fig. 5 or 6. The same effect as that of the PS control can be obtained by using a PIR controller.

[0073] As described above, PIR control is applied to the current controller provided in the current controller in the controller according to embodiment 2. Even when PIR control is applied instead of PS control, the same effects as those in embodiment 1 can be obtained.

[0074] Embodiment 3 14 is a diagram showing a configuration example of a refrigeration cycle-applied device 900 according to embodiment 3. The refrigeration cycle-applied device 900 according to embodiment 3 includes the rotating machine drive device 8 described in embodiment 1. The refrigeration cycle-applied device 900 according to embodiment 3 can be applied to products equipped with a refrigeration cycle, such as air conditioners, refrigerators, freezers, and heat pump water heaters.

[0075] The refrigeration cycle device 900 includes a compressor 42 incorporating the motor 41 in the first embodiment, a four-way valve 902, an indoor heat exchanger 906, an expansion valve 908, and an outdoor heat exchanger 910 attached via refrigerant piping 912. Inside the compressor 42, there are provided a compression mechanism 904 that compresses the refrigerant, and a motor 41 that operates the compression mechanism 904. The refrigeration cycle device 900 can perform heating or cooling operation by switching the four-way valve 902.

[0076] The compression mechanism 904 is driven by a variable-speed controlled motor 41. During heating operation, as indicated by the solid arrows, the refrigerant is pressurized by the compression mechanism 904 and discharged, passes through the four-way valve 902, the indoor heat exchanger 906, the expansion valve 908, the outdoor heat exchanger 910, and the four-way valve 902, and returns to the compression mechanism 904. During cooling operation, as indicated by the dashed arrows, the refrigerant is pressurized by the compression mechanism 904 and discharged, passes through the four-way valve 902, the outdoor heat exchanger 910, the expansion valve 908, the indoor heat exchanger 906, and the four-way valve 902, and returns to the compression mechanism 904. During heating operation, the indoor heat exchanger 906 acts as a condenser to release heat, and the outdoor heat exchanger 910 acts as an evaporator to absorb heat. During cooling operation, the outdoor heat exchanger 910 acts as a condenser to release heat, and the indoor heat exchanger 906 acts as an evaporator to absorb heat. The expansion valve 908 reduces the pressure of the refrigerant and causes it to expand.

[0077] The refrigeration cycle applied device 900 according to the third embodiment has been described as including the rotating machine driving device 8 described in the first embodiment, but is not limited to this. The refrigeration cycle applied device 900 may include the rotating machine driving device 8 including the rectifier circuit 20 described in the second embodiment. Furthermore, the rotating machine driving device 8 may include a rectifier circuit other than the rectifier circuit 20 described in the first or second embodiment, as long as the control method of the first or second embodiment can be applied.

[0078] The configurations shown in the above embodiments are merely examples, and may be combined with other known technologies, or the embodiments may be combined with each other, or part of the configuration may be omitted or modified without departing from the spirit of the invention. For example, the above-described control method may also be applied to a DC-AC converter. [Explanation of symbols]

[0079] 1 AC power source, 2 AC-DC converter, 3 DC-AC converter, 4 load, 6 control unit, 7 current control system, 8 rotating machine drive unit, 9a, 9b DC bus, 20 rectifier circuit, 41 motor, 42 compressor, 61 voltage control unit, 62 current control unit, 63 switching signal generation unit, 72 controller, 73 controlled plant, 74, 624 target value filter, 211 current detection unit, 212 reactor, 213a, 213b single-phase diode bridge cell, 215 switching element, 216 capacitor, 217a, 217b voltage detection unit, 218 diode, 225 switching cell, 611 voltage controller, 612, 622 subtractor, 621 current controller, 623 multiplier, 630 scaling unit, 631 carrier signal generator, 632 Comparator, 900 refrigeration cycle application equipment, 902 four-way valve, 904 compression mechanism, 906 indoor heat exchanger, 908 expansion valve, 910 outdoor heat exchanger, 912 refrigerant piping.

Claims

1. a rectifier circuit having at least one switching element and rectifying a power supply voltage applied from an AC power supply; a capacitor connected to a DC bus for smoothing an output voltage of the rectifier circuit; a reactor that is disposed closer to the AC power source than the capacitor; a control unit that generates a switching signal for controlling the switching element; Equipped with the switching element is disposed closer to the AC power supply than the capacitor; The control unit generates the switching signal so that harmonic components included in a power supply current flowing between the AC power supply and the rectifier circuit comply with a harmonic standard value of the power supply current, and the number of switching operations in one period of a power supply voltage when the switching element performs a switching operation is one or more times and is equal to or less than a value obtained by dividing a carrier frequency, which is a frequency of a carrier signal, by a frequency of the power supply voltage.

1. An AC / DC converter comprising:

2. The control unit is a voltage control unit that generates a first current command value using a first voltage command value that is a command value of a bus voltage that is a voltage of the DC bus; a current control unit that generates a second voltage command value using a second current command value obtained by making the first current command value follow a sine wave; a switching signal generating unit that generates the switching signal by using the second voltage command value; 2. The AC / DC converter according to claim 1, further comprising:

3. The current control unit includes a current controller configured as a proportional sine wave controller, a proportional integral sine wave controller, or a proportional integral resonant controller.

3. The AC / DC converter according to claim 2.

4. a current detection unit that detects the power supply current; A first voltage detection unit that detects the bus voltage; a second voltage detection unit that detects the power supply voltage; Equipped with the first current command value is generated using a voltage deviation that is a difference between the first voltage command value and a detection voltage detected by the first voltage detection unit, the sine wave is generated based on a voltage phase detected by the second voltage detection unit, The second voltage command value is generated using a current deviation that is a difference between the second current command value and a current detected by the current detection unit.

3. The AC / DC converter according to claim 2.

5. The power supply current has low-order harmonics superimposed thereon.

3. The AC / DC converter according to claim 2.

6. The current control unit includes a filter that operates a zero point of a feedback loop that feeds back the second voltage command value output by the current control unit to an input stage of the second current command value.

3. The AC / DC converter according to claim 2.

7. A rotary machine drive device comprising the AC / DC converter according to any one of claims 1 to 6.

8. A refrigeration cycle device comprising the AC / DC converter according to any one of claims 1 to 6.

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