Ac-DC conversion device, rotary machine drive device, and refrigeration cycle application equipment

Abstract

An AC-DC conversion device (2) comprises: a rectifier circuit (20) which has at least one switching element (215) to rectify a power supply voltage supplied from an AC power supply (1); a capacitor (216) which smooths the output voltage of the rectifier circuit (20); a reactor (212) which is disposed closer to the AC power supply (1) than the capacitor (216) is; a control part (6) which generates a switching signal for controlling the switching element (215); and a current detection part (210) which is connected to the switching element (215) in series, wherein the switching element (215) is disposed closer to the AC power supply (1) than the capacitor (216) is, and the control part (6) uses the power supply voltage, the inductance value of the reactor (212), the terminal voltage of the capacitor (216), and a duty ratio in which the switching element (215) is turned off in a predetermined period to estimate a power supply current which flows through the reactor (212) when the switching element (215) is off.

Description

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

[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.

[0002] A power factor correction circuit is typically used to obtain DC voltage from an AC power source. A power factor correction circuit maintains a constant bus voltage and controls the power supply current to comply with harmonic standards. A power factor correction circuit and its control method, the "simple switching method" (also known as the "partial switching method"), performs switching at least once per half cycle of the power supply voltage, which is the voltage of the AC power supply. This method has the advantage 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 can distort the power supply current.

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

[0004] Japanese Patent Application Laid-Open No. 2000-125545

[0005] However, the conventional technology described in Patent Document 1 involves a method of repeatedly verifying compliance with harmonic standards, resulting in a problem that the number of trials exponentially increases as the number of pulses increases. Furthermore, there is a problem that the design process for control gains is time-consuming because there are no clear guidelines for quantitatively and uniquely designing them. To address this problem, a method for suppressing power supply harmonics is available that uses a PS (Proportional Sinusoidal) controller, in which an S (Sinusoidal) controller with high tracking performance for sinusoidal command signals is connected in parallel to a P (Proportional) controller. However, while such control circuits typically use current values ​​detected by a current detector, current detectors with high detection accuracy, such as direct current transformers (DCCTs), are expensive. While inexpensive current detectors are available, they suffer from issues such as low detection accuracy.

[0006] The present disclosure has been made in consideration of the above, and aims to provide an AC / DC conversion device that can comply with harmonic standards without relying on trial and error adjustments, while suppressing increases in circuit costs and decreases in current detection accuracy.

[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 having at least one switching element that rectifies a power supply voltage applied from a single-phase AC power supply; a capacitor connected to a DC bus that smoothes the output voltage of the rectifier circuit; a reactor that is arranged closer to the single-phase AC power supply than the capacitor; a controller that generates a switching signal to control the switching element; and a current detection circuit using a shunt resistor connected in series with the switching element. The switching element is arranged closer to the single-phase AC power supply than the capacitor. The controller estimates the power supply current that flows through the reactor when the switching element is off using the power supply voltage, the inductance value of the reactor, the terminal voltage of the capacitor, and a duty ratio that indicates the proportion of time that the switching element is off during a specified period, and generates the switching signal.

[0008] The AC-DC converter according to the present disclosure has the advantage of being able to comply with harmonic standards without relying on trial-and-error adjustments, while suppressing increases in circuit costs and decreases in current detection accuracy.

[0009] FIG. 1 is a block diagram showing a configuration example of a rotary machine drive device according to a first embodiment; FIG. 2 is a circuit diagram showing a configuration example of an AC / DC converter according to a first embodiment; FIG. 3 is a diagram showing a configuration example of a control unit provided in the AC / DC converter according to the first embodiment; FIG. 4 is a diagram showing example operation waveforms of a power supply voltage, a bus voltage, and a power supply current when the control unit of the AC / DC converter according to the first embodiment is provided with a PS controller; FIG. 5 is a diagram showing an example of current harmonic characteristics when the control unit of the AC / DC converter according to the first embodiment is provided with a PS controller; FIG. 1 shows a configuration example when viewed as a Modulation circuit. Circuit diagram showing a configuration example of an AC / DC converter according to embodiment 2. Flowchart showing the control contents of the control unit of the AC / DC converter according to embodiment 2. FIG. 1 shows an example of operation waveforms when the control unit of the AC / DC converter according to embodiment 2 uses the power supply current at the immediately previous sampling timing when the switching element is turned off. FIG. 1 shows a configuration example of an AC / DC converter according to embodiment 3. FIG. 1 shows a configuration example of an AC / DC converter according to embodiment 4. FIG. 1 shows a configuration example of an AC / DC converter according to embodiment 5. FIG. 1 shows a configuration example of an AC / DC converter according to embodiment 6. FIG. 1 shows a configuration example of an AC / DC converter according to embodiment 7. FIG. 1 shows a configuration example of an AC / DC converter according to embodiment 8. FIG. 1 shows a configuration example of an AC / DC converter according to embodiment 9. FIG. 1 shows a configuration example of an AC / DC converter according to embodiment 10. FIG.

[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. Fig. 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 supply 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. The AC power supply 1 is a single-phase AC power supply that applies a power supply voltage to the AC-DC converter 2. 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 embodiment 1. The AC-DC converter 2 according to embodiment 1 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 210 and voltage detection units 217a and 217b as means for detecting voltage or current.

[0013] The rectifier circuit 20 includes single-phase diode bridge cells 213a and 213b, each of which is formed by connecting four diodes in a bridge configuration, 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 source 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 is located closer to the AC power source 1 than the capacitor 216. The switching element 215 performs a switching operation at least once per half cycle of the power source voltage. In this way, the rectifier circuit 20 includes at least one switching element 215 and rectifies the power source voltage applied from the AC power source 1.

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

[0015] The voltage detection unit 217b detects the bus voltage V ｄｃ The voltage detection unit 217a detects the power supply voltage. The current detection unit 210 is a current detection circuit that uses a shunt resistor connected in series to the switching element 215. The current detection unit 210 detects the current that flows through the switching element 215 when the switching element 215 is on.

[0016] The control unit 6 receives the detection values ​​of the voltage detection units 217a and 217b and the current detection unit 210. 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 insulated gate bipolar transistor (IGBT) as 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 metal-oxide-semiconductor field-effect transistor (MOSFET).

[0018] 2 is configured as a closed loop using the detected values ​​of the voltage detectors 217a, 217b and the current detector 210, but may be configured as an open loop using a target value, an estimated value, etc. When the AC-DC converter 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 detectors 217a, 217b and the current detector 210.

[0019] As described above, the control unit 6 generates a switching signal based on the detection values ​​of the voltage detection units 217a, 217b and the current detection unit 210. There are various methods for the control unit 6 to generate a switching signal, but here, a case where the control unit 6 performs current PS control will be described. Fig. 3 is a diagram showing an example of the configuration of the control unit 6 provided in the AC-DC converter 2 according to the first embodiment. The control unit 6 includes a PS controller 60, which is a current controller that performs current PS control. The transfer function G when current PS control is performed in a configuration using the PS controller 60 as shown in Fig. 3 is ＡＣＲ（ｓ） can be expressed by the following equation (1).

[0020]

[0021] In equation (1), ACR stands for Automatic Current Regulator. 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 60, the proportional gain K ｐＡＣＲ , S control gain K ｓＡＣＲ and angular frequency ω ｎ can be determined arbitrarily. PS control is a control that introduces S control, which is a Laplace transform expression of a cos function, in addition to proportional control (P control). As shown in FIG. 3, the PS controller 60 is configured such that an upper P controller is connected in parallel with a lower S controller. The S controller controls the angular frequency ω ｎ It has the feature of improving the tracking performance for sinusoidal input. In the S controller, the angular frequency ω ｎ The reason why 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, it can track the command value without deviation.

[0022] In the configuration shown in FIG. 3, the control unit 6 controls the current command value I Ｌ ＊ and the excitation signal. Ｌ ＊Alternatively, a target value filter may be provided on the input side of the PS controller 60, which is a filter for canceling out zeros of the transfer function with the poles of the filter and adjusting the response of the transfer function. The configuration of the control unit 6 shown in Fig. 3 shows a configuration in which the control unit 6 generates a switching signal, but the portions preceding and succeeding the PS controller 60 have a general configuration and therefore will not be described in detail. The operation of the estimation unit 61, which is a current estimator, will be described later.

[0023] Furthermore, the control unit 6 includes a PS controller 60 as a current controller, but the configuration of the PS controller 60 is not limited to the example shown in Fig. 3. For example, the control unit 6 may include a PS controller 60 including a plurality of S controllers. In this manner, the control unit 6 includes the PS controller 60, which is a current controller that controls the power supply current of the AC power supply 1, and the PS controller 60, which is a current controller, includes at least one controller that satisfies the internal model principle for a sine wave.

[0024] FIG. 4 shows the power supply voltage and bus voltage V when the control unit 6 of the AC-DC converter 2 according to the first embodiment includes a PS controller 60. ｄｃ 4 is a diagram showing an example of the operating waveforms of the bus voltage V ｄｃ 4 shows the waveforms of the absolute value of the power supply voltage and the detected power supply current, the fundamental component of the detected power supply current, and the power supply current command value. As shown in the lower part of FIG. 4, the fundamental component of the detected power supply current is almost equal to the power supply current command value. From this, if a PS controller 60 with high tracking performance for sine wave input is applied to the control unit 6, the bus voltage V ｄｃ It can be seen that even under the condition that the bus voltage V is equal to or less than the peak value of the absolute value of the power supply voltage, the fundamental wave of the detected power supply current can follow the power supply current command value. ｄｃ The results are for operating conditions where the absolute value of the power supply voltage is less than the peak value. ｄｃ It goes without saying that even under operating conditions where the absolute value of the power supply voltage exceeds the peak value, the fundamental wave of the detected power supply current follows the power supply current command value.

[0025] FIG. 5 shows an example of current harmonic characteristics when the control unit 6 of the AC-DC converter 2 according to the first embodiment includes a PS controller 60. The current harmonic standard used in FIG. 5 is IEC (International Electrotechnical Commission) 61000-3-2 Class A. Note that IEC 61000-3-2 Class A is an example of a current harmonic standard, and the current harmonic standard is not limited to this standard. In FIG. 5, the solid lines indicate the second through fortieth current harmonic standard values ​​specified in IEC 61000-3-2 Class A. Also, in FIG. 5, the dashed lines indicate the effective values ​​of the second through fortieth harmonic components during rated operation. The harmonic components during rated operation represent the remaining components of the power supply current flowing when the AC-DC converter 2 is operated at rated power, excluding the fundamental component of the power supply current. In this paper, the second through fortieth harmonics are defined as "low-order harmonics." According to Figure 5, 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 a PS controller 60 with high tracking performance for sine wave input is applied to the control unit 6, the low-order harmonics contained in the power supply current will comply with the harmonic standard value for the power supply current. Note that Figure 5 shows the harmonic components during rated operation as an example, but it goes without saying that the effect of suppressing harmonic components by the PS controller 60 can be obtained even during times other than rated operation.

[0026] The control unit 6 performs control to suppress harmonic components by treating the current flowing through the switching element 215 detected by the current detection unit 210 as the current flowing through the reactor 212, i.e., the power supply current. Here, as described above, the current detection unit 210 detects the current flowing through the switching element 215 when the switching element 215 is on. That is, the current detection unit 210 cannot detect the current flowing through the switching element 215 when the switching element 215 is off. The control unit 6 cannot obtain current information from the current detection unit 210 when the switching element 215 is off. Therefore, in this embodiment, the control unit 6 performs control to suppress harmonic components by estimating the power supply current during periods when the current detection unit 210 cannot detect the current, that is, by complementing the detected current.

[0027] 6 shows the absolute value of the power supply voltage and the bus voltage V ｄｃ 6A and 6B are diagrams showing examples of operational waveforms of the power supply current and the shunt current detected by the current detection unit 210. The upper part of Fig. 6 is similar to the upper part of Fig. 4. In Fig. 6, the section in the middle where the power supply current changes slightly is the section where the switching element 215 is turned on and off, and the section in the lower part where the shunt current is detected as a current value other than 0 is the section where the switching element 215 is on.

[0028] In order to perform feedback control, i.e., current PS control, when the shunt current is changing as shown in Fig. 6 , the control unit 6 needs to estimate the shunt current as the power supply current in a section where the shunt current is not detected between sections where the shunt current is detected, i.e., in a section where the switching element 215 is off. Therefore, the control unit 6 uses the estimation unit 61 shown in Fig. 3 to estimate the shunt current as the power supply current in a section where the switching element 215 is off. Specifically, the operation of the estimation unit 61 of the control unit 6 that estimates the shunt current as the power supply current in a section where the switching element 215 is off will be described. First, a circuit model used for current estimation is derived.

[0029] 7 is a diagram showing a configuration example of the AC-DC converter 2 according to the first embodiment as a simple PAM circuit. The simple PAM circuit shown in FIG. 7 simply represents the AC-DC converter 2 shown in FIG. 2, and the load 4 is used as a current source 242. The voltage v applied to the reactor 212 shown in FIG. Ｌ The differential equation derived from the above is shown in equation (2). Also, the current i related to the capacitor 216 is Ｃ The differential equation derived from this is shown in equation (3).

[0030]

[0031]

[0032] In equation (2), L is the inductance value of the reactor 212, and i Ｌis the current flowing through the reactor 212, i.e., the power supply current i ｓ and V ｉｎ is the power supply voltage supplied from the AC power supply 1, and v ｃｏｎｖ is the converter voltage output from the rectifier circuit 20. In addition, in equation (3), C is the capacitance of the capacitor 216, and i ｃｏｎｖ is the converter current output from the rectifier circuit 20, and i ｏｕｔ is the current flowing through the current source 242. Here, the converter voltage v output from the rectifier circuit 20 varies depending on the on / off state of the switching element 215. ｃｏｎｖ and converter current i ｃｏｎｖ The converter voltage v when the on / off state of the switching element 215 is taken into consideration ｃｏｎｖ is shown in equation (4). In addition, when the on / off state of the switching element 215 is taken into consideration, the converter current i ｃｏｎｖ is shown in equation (5). Note that Sw:ON indicates when the switching element 215 is on, and Sw:OFF indicates when the switching element 215 is off.

[0033]

[0034]

[0035] In equation (4), V ｏｕｔ is the terminal voltage of the capacitor 216, i.e., the bus voltage V ｄｃ In addition, in equation (5), i ｓ is the power supply current. Next, from equations (2) to (5), the state equations of the circuit when the switching element 215 is on and when it is off are derived. The state equation when the switching element 215 is on is shown in equation (6). Furthermore, the state equation when the switching element 215 is off is shown in equation (7).

[0036]

[0037]

[0038] Here, the on-duty, which is the duty ratio when the switching element 215 is on, is D, and the off-duty, which is the duty ratio when the switching element 215 is off, is D'. If we multiply each state equation by D and D' and take the weighted average, we get equation (8).

[0039]

[0040] Note that D+D'=1. Extracting the first line of equation (8) yields equation (9).

[0041]

[0042] In equation (9), the power supply current i ｓ , off-duty D', terminal voltage V of the capacitor 216 which is the output voltage to the load 4 ｏｕｔ , and the power supply voltage V ｉｎ Since is a time variable, equation (9) can be rewritten as equation (10).

[0043]

[0044] When Euler's method is applied to the equation (10) with respect to the sampling time T, the equation (11) is obtained.

[0045]

[0046] Here, the subscript n represents the variable of the current sample, and n+1 represents the variable of the next sample. Since the off-duty D' is an argument, the estimation unit 61 of the control unit 6 uses the equation (11) during the period when no current flows through the shunt resistor of the current detection unit 210 to estimate the power supply current i ｓ It can be seen that estimation by the estimation unit 61 of the control unit 6 is possible because the right-hand side of equation (11) represents all n current samples, while the left-hand side of equation (11) represents the next n+1 sample. Here, if the definition of off-duty D' is in the range of 0 to 1, a correction such as equation (12) is required.

[0047]

[0048] In addition, the power supply current i ｓIf there is a period of DCM (Discontinuous Conduction Mode), the process shown in equation (13) is required.

[0049]

[0050] The estimation unit 61 of the control unit 6 estimates the power supply current i ｓ In estimating the power supply current i, it may be derived directly using equation (11), or it may be calculated using an evaluation function that suppresses variations in the inductance value L of the reactor 212 and harmonics in equation (11). ｓ When estimating, the resistance component of the reactor 212 may be taken into account in equation (11). As shown in FIG. 3, the estimation unit 61 performs processing after the calculation of the PS controller 60 is completed and the off-duty D' is calculated, and estimates the power supply current i ｓＦＢ When the switching element 215 is on, the estimation unit 61 may stop the calculation of equation (11) and update only the current value. When the switching element 215 is on, the estimation unit 61 may also estimate the power supply current i ｓ Since the true value of the power supply current i ｓ and the power supply current i calculated by the estimation unit 61. ｓＦＢ and perform state feedback on the comparison result, or use model predictive control to replace the current controller and the signal generation mechanism by carrier comparison.

[0051] In this way, the control unit 6 controls the power supply voltage V applied from the AC power supply 1. ｉｎ , the inductance value L of the reactor 212, and the terminal voltage V of the capacitor 216. ｏｕｔ , and an off-duty D' which is a duty ratio indicating the rate at which the switching element 215 is turned off in a specified period, the power supply current i flowing through the reactor 212 when the switching element 215 is off is calculated. ｓＦＢ is estimated and a switching signal is generated.

[0052] As described above, according to this embodiment, in a simple switching circuit including a current detection unit 210 using a shunt resistor connected in series with a switching element 215 in a short-circuit path having the switching element 215, the control unit 6 of the AC / DC converter 2 detects a power supply current i when the switching element 215 is off. ｓ During the period when the shunt current cannot be detected, the power supply current i ｓＦＢ This allows the control unit 6 to comply with harmonic standards without relying on trial and error adjustments, while suppressing increases in circuit costs and decreases in current detection accuracy.

[0053] Second Embodiment In a second embodiment, a case will be described in which the AC / DC converter 2 further includes a current detector at the upstream or downstream of the reactor 212.

[0054] 8 is a circuit diagram showing a configuration example of an AC-DC converter 2 according to the second embodiment. The AC-DC converter 2 shown in FIG. 8 is obtained by adding a current detection unit 211 to the AC-DC converter 2 according to the first embodiment shown in FIG. 2. The current detection unit 211 detects the power supply current i flowing between the AC power supply 1 and the rectifier circuit 20. ｓ , that is, the current i flowing through the reactor 212 Ｌ 8, the current detection unit 211 is arranged in the upstream stage of the reactor 212, but is not limited thereto and may be arranged in the downstream stage of the reactor 212. Here, the current detection unit 211 is an ACCT (Alternating Current Transformer). In the following description, the current detection unit 211, which is an ACCT, may be referred to as an AC current transformer. Generally, an ACCT has a problem in that its detection accuracy deteriorates near the current zero crossing. Therefore, in this embodiment, the control unit 6 uses the current detection value by the current detection unit 210 using a shunt resistor or the power supply current i estimated by the estimation unit 61 in a region where the detection accuracy of the current detection unit 211, which is an ACCT, deteriorates. ｓＦＢ By using this, deterioration of detection accuracy is suppressed.

[0055] 9 is a flowchart showing the control contents of the control unit 6 of the AC / DC converter 2 according to the second embodiment. In the following description, (n) and (n-1) indicate sampling timings. For example, the sampling timing of (n-1) is the sampling timing immediately before the sampling timing of (n). ＡＣＣＴ (n) indicates the current value detected by the current detection unit 211, which is ACCT, at the sampling timing of (n). ｔｈ is a defined threshold value indicating the current value at which the detection accuracy of the current detection unit 211, which is the ACCT, deteriorates. ＡＣＣＴ (n) is the threshold i ｔｈ In the above cases, good detection accuracy can be obtained in the current detection unit 211. ｔｈ Regarding this, the minimum detectable current value defined by the manufacturer of the current detection unit 211, which is the ACCT, may be used, or the detection accuracy of the current detection unit 211, which is the ACCT, may be actually measured and a current value that can guarantee accuracy may be used as the threshold value, and the setting method is not particularly limited.

[0056] i ｓ (n) is the final power supply current i at the sampling timing of (n) ｓ The detected value of i is shown. ｓｈ (n) indicates the current value detected by the current detection unit 210 using a shunt resistor at the sampling timing of (n). sign is a sign function, and the argument power supply voltage v ｓ The sign is returned according to the polarity of (n). The argument of the sign function sign is the power supply voltage v ｓ Instead of (n), a current command value, a phase locked by a PLL (Phase Locked Loop), a current value at the previous sampling timing, etc. may be used. ｓＦＢ (n) is the power supply current estimated by the estimation unit 61 at the sampling timing of (n).

[0057] First, the control unit 6 detects the current value i ＡＣＣＴ (n) is the threshold i ｔｈThe control unit 6 determines whether the current value i detected by the current detection unit 211 is equal to or greater than the predetermined value i (step S1). ＡＣＣＴ (n) is the threshold i ｔｈ In the above cases (step S1: Yes), good detection accuracy can be obtained in the current detection unit 210, so the power supply current i ｓ (n) is the current value i detected by the current detection unit 211. ＡＣＣＴ The control unit 6 uses the current value i(n) detected by the current detection unit 211 (step S2). ＡＣＣＴ (n) is the threshold i ｔｈ If it is less than this (step S1: No), good detection accuracy cannot be obtained in the current detection unit 210, so it is next determined whether the switching element 215 is on or off (step S3).

[0058] When the switching element 215 is on (step S3: Yes), a current flows through the current detection unit 210 using a shunt resistor, so the control unit 6 detects the power supply current i ｓ (n) is the current value i detected by the current detection unit 210. ｓｈ (n) with the sign function sign(v ｓ (n)) is multiplied and used (step S4). ｓｈ Since (n) has only positive polarity, the control unit 6 controls the power supply voltage v ｓ If the switching element 215 is off (step S3: No), no current flows through the current detection unit 210 using a shunt resistor, so the control unit 6 determines that the power supply current i ｓ (n) is the power supply current i estimated by the estimation unit 61. ｓＦＢ (n) is adopted (step S5).

[0059] In this way, the control unit 6 detects the current value i ＡＣＣＴ (n) is the defined threshold i ｔｈ In the above cases, the current value i detected by the current detection unit 211 ＡＣＣＴ(n) is used to generate a switching signal, and the current value i detected by the current detection unit 211 is ＡＣＣＴ (n) is the threshold i ｔｈ If it is less than 1, the current value i flowing through the shunt resistor detected by the current detection unit 210 is ｓｈ (n) or the power supply current i estimated by the estimation unit 61 ｓＦＢ (n) is used to generate the switching signal.

[0060] When the switching element 215 is off (step S3: No), the control unit 6 calculates the power supply current i ｓ (n) is the power supply current i estimated by the estimation unit 61. ｓＦＢ The power supply current i at the sampling timing (n-1), which is the previous sampling timing, is used instead of (n). ｓ (n-1) may also be adopted.

[0061] FIG. 10 shows the power supply current i at the previous sampling timing when the control unit 6 of the AC / DC converter 2 according to the second embodiment turns off the switching element 215. ｓ 10 is a diagram showing an example of an operation waveform when the control unit 6 uses the power supply current i (n-1) at the previous sampling timing in the section where the waveform of the true current value becomes horizontal around 0 A. ｓ As a result of adopting (n-1), it is shown that there is a slight error between the true current value and the detected current. Here, the section where the waveform of the true current value becomes horizontal around 0 A is also the region where the detection accuracy of the current detection unit 211, which is ACCT, deteriorates. Therefore, although there is a possibility that a slight error occurs, the control unit 6 calculates the power supply current i at the previous sampling timing. ｓ By adopting (n-1), it is possible to suppress a decrease in the accuracy of current detection.

[0062] As described above, according to this embodiment, in a simple switching circuit including a current detection unit 210 using a shunt resistor connected in series with a switching element 215 in a short-circuit path having the switching element 215, the control unit 6 of the AC / DC converter 2 detects a power supply current i when the switching element 215 is off. ｓDuring the period when the shunt current cannot be detected, the power supply current i ｓＦＢ The current value i detected by the current detection unit 211, which is an ACCT arranged in the front or rear stage of the reactor 212, is estimated to complement the detected current. ＡＣＣＴ In this case, the control unit 6 can also comply with the harmonic standards without relying on trial and error adjustments, while suppressing an increase in circuit costs and a decrease in current detection accuracy.

[0063] Embodiment 3 In embodiment 3, a different example of the AC-DC converter 2 including the control unit 6 described in embodiments 1 and 2 will be described. Note that components having the same or equivalent functions as components of the AC-DC converter 2 described in embodiments 1 and 2 will be denoted by the same reference numerals, and overlapping descriptions will be omitted.

[0064] FIG. 11 is a diagram illustrating a configuration example of an AC-DC converter 2 according to a third embodiment. In the AC-DC converter 2 of FIG. 11, the rectifier circuit 20 has a configuration called a full-PAM 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. In the third embodiment, a configuration is described in which PIR (Proportional Integral Resonant) control is applied as control by the control unit 6 of the AC-DC converter 2.

[0065] 2 and 8 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. 8 is disposed between the single-phase diode bridge cell 213a and the diode 218.

[0066] 2, 8, and 11, the positions and connection forms of the switching element 215 and the reactor 212 are different, but in all of the configurations, the switching element 215 and the reactor 212 are arranged closer to the AC power source 1 than the capacitor 216. This arrangement relationship is similar to other embodiments described later. Also, although the current detection unit 210 is not shown in FIG. 11, the position of the current detection unit 210 is not particularly important as long as it is connected in series with the switching element 215. This arrangement relationship is similar to other embodiments described later. Also, the same applies to other embodiments in which a plurality of switching elements are provided.

[0067] 11, 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. 11 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.

[0068] 11 may be used in the first and second embodiments, and the simple switching circuits of the first and second embodiments may be used in the third 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.

[0069] Next, the transfer function of the PIR controller will be described. First, the transfer function G ＰＩＲ（ｓ） can be expressed by the following equation (14).

[0070]

[0071] In the above formula (14), K ｐ is the proportional gain, and K ｉ is the integral gain, and K ｒ is the resonance control gain, and ω １is the angular frequency of the current control response, and ω ２ is the angular frequency of the sine wave command to be followed. ＰＩＲ（ｓ） A PIR controller having the above formula may be applied to the control unit 6 of the first and second embodiments. The use of a PIR controller can also provide the same effects as the PS control.

[0072] As described above, PIR control is applied to the control unit 6 according to the third embodiment. Even when PIR control is applied instead of PS control, the same effects as those of the first and second embodiments can be obtained.

[0073] Embodiment 4 In embodiment 4, a different example of the AC-DC converter 2 including the control unit 6 described in embodiments 1 and 2 will be described. Note that components having the same or equivalent functions as components of the AC-DC converter 2 described in embodiments 1 and 2 will be denoted by the same reference numerals, and overlapping descriptions will be omitted.

[0074] Fig. 12 is a diagram showing a configuration example of an AC-DC converter 2 according to embodiment 4. In the AC-DC converter 2 shown in Fig. 12, a rectifier circuit 20 is configured with a single-phase H-bridge cell including four switching elements 220a, 220b, 220c, and 220d. Note that the configuration and operation of the rectifier circuit 20 shown in Fig. 12 are publicly known, and further description thereof will be omitted here.

[0075] The control unit 6 generates switching signals to drive the four switching elements 220a, 220b, 220c, and 220d using the control methods described in the first and second embodiments. As a result, the AC-DC converter 2 shown in Fig. 12 can also achieve the same effects as those of the first and second embodiments.

[0076] 12, the switching elements 220a, 220b, 220c, and 220d are shown as IGBTs, but any elements capable of switching operation may be used. Furthermore, although the AC-DC converter 2 shown in FIG. 12 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.

[0077] Embodiment 5 In embodiment 5, a different example of the AC-DC converter 2 including the control unit 6 described in embodiments 1 and 2 will be described. Note that components having the same or equivalent functions as components of the AC-DC converter 2 described in embodiments 1 and 2 will be denoted by the same reference numerals, and overlapping descriptions will be omitted.

[0078] FIG. 13 is a diagram illustrating a configuration example of an AC-DC converter 2 according to a fifth embodiment. In the AC-DC converter 2 of FIG. 13, a rectifier circuit 20 is configured with a single-phase H-bridge cell including two diodes 218a and 218b and two switching elements 220c and 220d. In the rectifier circuit 20 illustrated in FIG. 13, one leg is configured with a series circuit of the diodes 218a and 218b, and the other leg is configured with a series circuit of the switching elements 220c and 220d. The configuration and operation of the rectifier circuit 20 illustrated in FIG. 13 are publicly known, and further description thereof will be omitted here.

[0079] The control unit 6 generates switching signals to drive the two switching elements 220c and 220d using the control methods described in the first and second embodiments. As a result, the AC-DC converter 2 shown in Fig. 13 can also achieve the same effects as those of the first and second embodiments.

[0080] 13, the switching elements 220c and 220d are shown as IGBTs, but any elements 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.

[0081] Embodiment 6 In embodiment 6, a different example of the AC-DC converter 2 including the control unit 6 described in embodiments 1 and 2 will be described. Note that components having the same or equivalent functions as components of the AC-DC converter 2 described in embodiments 1 and 2 will be denoted by the same reference numerals, and overlapping descriptions will be omitted.

[0082] FIG. 14 is a diagram illustrating a configuration example of an AC-DC converter 2 according to a sixth embodiment. In the AC-DC converter 2 of FIG. 14, a rectifier circuit 20 is configured with a single-phase H-bridge cell including two diodes 218a and 218c and two switching elements 220b and 220d. In the rectifier circuit 20 illustrated in FIG. 14, the diodes 218a and 218c are arranged in the upper arms of the two legs, and the switching elements 220b and 220d are arranged in the lower arms of the two legs. Note that the configuration and operation of the rectifier circuit 20 illustrated in FIG. 14 are publicly known, and therefore further description thereof will be omitted here.

[0083] The control unit 6 generates switching signals to drive the two switching elements 220b and 220d using the control methods described in the first and second embodiments. As a result, the AC-DC converter 2 shown in Fig. 14 can also achieve the same effects as those of the first and second embodiments.

[0084] 14, the switching elements 220b and 220d are shown as IGBTs, but any elements capable of switching operation may be used. Furthermore, although the AC-DC converter 2 shown in FIG. 14 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.

[0085] Embodiment 7 In embodiment 7, a different example of the AC-DC converter 2 including the control unit 6 described in embodiments 1 and 2 will be described. Note that components having the same or equivalent functions as components of the AC-DC converter 2 described in embodiments 1 and 2 will be denoted by the same reference numerals, and overlapping descriptions will be omitted.

[0086] Fig. 15 is a diagram showing a configuration example of an AC-DC converter 2 according to a seventh embodiment. In the AC-DC converter 2 shown in Fig. 15, the rectifier circuit 20 is configured with a single-phase H-bridge cell including two diodes 218a and 218b, four switching elements 220a, 220b, 220c, and 220d, a capacitor 216b, and a voltage detection unit 217c. The voltage detection unit 217c may be provided outside the rectifier circuit 20. Note that in Fig. 15, the capacitor 216 shown previously is represented as a capacitor 216a.

[0087] In the rectifier circuit 20 shown in FIG. 15 , one leg is formed by a series circuit of diodes 218a and 218b, and the other leg is formed by a series circuit of switching elements 220a, 220b, 220c, and 220d. Capacitor 216b is connected between the connection point of switching elements 220a and 220b and the connection point of switching elements 220c and 220d. Voltage detection unit 217c detects the voltage of capacitor 216b and outputs the detected value to control unit 6. Based on the detected values ​​of voltage detection units 217a, 217b, and 217c and current detection unit 211, control unit 6 generates switching signals for controlling switching elements 220a, 220b, 220c, and 220d. Note that the configuration and operation of the rectifier circuit 20 shown in FIG. 15 are publicly known, and further description thereof will be omitted here.

[0088] The control unit 6 generates switching signals to drive the four switching elements 220a, 220b, 220c, and 220d using the control methods described in the first and second embodiments. As a result, the AC-DC converter 2 shown in Fig. 15 can also achieve the same effects as those of the first and second embodiments.

[0089] 15, the switching elements 220a, 220b, 220c, and 220d are shown as IGBTs, but any elements capable of switching operation may be used. Furthermore, although the AC-DC converter 2 shown in FIG. 15 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, 217b, and 217c and the current detector 211 do not need to be used.

[0090] Embodiment 8 In embodiment 8, a different example of the AC-DC converter 2 including the control unit 6 described in embodiments 1 and 2 will be described. Note that components having the same or equivalent functions as components of the AC-DC converter 2 described in embodiments 1 and 2 will be denoted by the same reference numerals, and overlapping descriptions will be omitted.

[0091] FIG. 16 is a diagram illustrating a configuration example of an AC-DC converter 2 according to an eighth embodiment. In the AC-DC converter 2 of FIG. 16, a rectifier circuit 20 includes a single-phase H-bridge cell 221 and a switching cell 222. The single-phase H-bridge cell 221 includes two diodes 218a and 218c and two switching elements 220b and 220d. The switching cell 222 includes four switching elements 220e, 220f, 220g, and 220h, a capacitor 216c, and a voltage detection unit 217c. The voltage detection unit 217c may be provided outside the switching cell 222.

[0092] In a single-phase H-bridge cell 221 shown in Fig. 16, diodes 218a and 218c are arranged in the upper arms of two legs, and switching elements 220b and 220d are arranged in the lower arms of two legs. In a switching cell 222 shown in Fig. 16, four switching elements 220e, 220f, 220g, and 220h are bridge-connected. A capacitor 216c is connected in parallel to a first leg consisting of switching elements 220e and 220f and a second leg consisting of switching elements 220g and 220h.

[0093] The voltage detection unit 217c detects the voltage of the capacitor 216c and outputs the detected value to the control unit 6. The control unit 6 generates switching signals for controlling the switching elements 220b, 220d, 220e, 220f, 220g, and 220h based on the detected values ​​of the voltage detection units 217a, 217b, and 217c and the current detection unit 211. The configuration and operation of the rectifier circuit 20 shown in FIG. 16 are publicly known, and further description thereof will be omitted here.

[0094] The control unit 6 generates switching signals to drive the six switching elements 220b, 220d, 220e, 220f, 220g, and 220h using the control methods described in the first and second embodiments. As a result, the AC-DC converter 2 shown in Fig. 16 can also achieve the same effects as those of the first and second embodiments.

[0095] 16, the switching elements 220b, 220d, 220e, 220f, 220g, and 220h are shown as IGBTs, but any elements capable of switching may be used. Furthermore, although the AC-DC converter 2 shown in FIG. 16 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, 217b, and 217c and the current detector 211 do not need to be used.

[0096] Embodiment 9 In embodiment 9, a different example of the AC-DC converter 2 including the control unit 6 described in embodiments 1 and 2 will be described. Note that components having the same or equivalent functions as components of the AC-DC converter 2 described in embodiments 1 and 2 will be denoted by the same reference numerals, and overlapping descriptions will be omitted.

[0097] FIG. 17 is a diagram illustrating a configuration example of an AC-DC converter 2 according to a ninth embodiment. In the AC-DC converter 2 of FIG. 17, the rectifier circuit 20 is composed of a single-phase diode bridge cell 213a and a switching cell 225. The switching cell 225 includes a single-phase diode bridge cell 213b and a series circuit formed by two switching elements 220a and 220b. The series circuit is connected in parallel to the single-phase diode bridge cell 213b. In FIG. 17, the capacitor 216 in FIGS. 2 and 8 is replaced with two capacitors 216a and 216b connected in series. The series-connected capacitors 216a and 216b are connected between the DC buses 9a and 9b.

[0098] The control unit 6 generates switching signals for controlling the switching elements 220a and 220b based on the detection values ​​of the voltage detection units 217a and 217b and the current detection unit 211. The configuration and operation of the rectifier circuit 20 shown in Fig. 17 are publicly known, and further description thereof will be omitted here.

[0099] The control unit 6 generates switching signals to drive the two switching elements 220a and 220b using the control methods described in the first and second embodiments. As a result, the AC-DC converter 2 shown in Fig. 17 can also achieve the same effects as those of the first and second embodiments.

[0100] 17, the switching elements 220a and 220b are shown as IGBTs, but any elements capable of switching operation may be used. Furthermore, although the AC-DC converter 2 shown in FIG. 17 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.

[0101] Embodiment 10 In embodiment 10, a different example of the AC-DC converter 2 including the control unit 6 described in embodiments 1 and 2 will be described. Note that components having the same or equivalent functions as components of the AC-DC converter 2 described in embodiments 1 and 2 will be denoted by the same reference numerals, and overlapping descriptions will be omitted.

[0102] FIG. 18 is a diagram illustrating a configuration example of an AC-DC converter 2 according to a tenth embodiment. In the AC-DC converter 2 of FIG. 18, a rectifier circuit 20 is configured with a single-phase diode bridge cell 213a and an interleaved cell 219. The interleaved cell 219 is a full-PAM circuit configuration with two sets of reactors, switching elements, and diodes. Specifically, the interleaved cell 219 includes reactors 2191a and 2191b, diodes 2192a and 2192b, and switching elements 2193a and 2193b. The configuration and operation of the rectifier circuit 20 illustrated in FIG. 18 are publicly known, and further description thereof will be omitted here.

[0103] The control unit 6 generates switching signals to drive the two switching elements 2193a and 2193b using the control methods described in the first and second embodiments. As a result, the AC-DC converter 2 shown in Fig. 18 can also achieve the same effects as those of the first and second embodiments.

[0104] Although the switching elements 2193a and 2193b are shown as IGBTs in FIG. 18 , any elements capable of switching operation may be used. Furthermore, although the AC-DC converter 2 shown in FIG. 18 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. Furthermore, although FIG. 18 shows an example in which the interleaved cells 219 are configured in two stages, the interleaved cells 219 may also be configured in three or more stages. Furthermore, the rectifier circuits 20 shown in the first to ninth embodiments may also be configured in an interleaved configuration.

[0105] Eleventh Embodiment Fig. 19 is a diagram showing a configuration example of a refrigeration cycle-applied device 900 according to an eleventh embodiment. The refrigeration cycle-applied device 900 according to the eleventh embodiment includes the rotating machine drive device 8 described in the first embodiment. That is, the refrigeration cycle-applied device 900 includes the AC-DC converter 2 described in the first embodiment. The refrigeration cycle-applied device 900 according to the eleventh embodiment can be applied to products equipped with a refrigeration cycle, such as air conditioners, refrigerators, freezers, and heat pump water heaters.

[0106] The refrigeration cycle device 900 includes a compressor 42 incorporating the motor 41 of the first embodiment, a four-way valve 902, an indoor heat exchanger 906, an expansion valve 908, and an outdoor heat exchanger 910, all of which are 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.

[0107] 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.

[0108] The refrigeration cycle applied device 900 according to the eleventh 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 any of the second to tenth embodiments. Furthermore, the refrigeration cycle applied device 900 may include a rectifier circuit other than the rectifier circuit 20 described in any of the first to tenth embodiments, as long as the control method of the first embodiment can be applied.

[0109] The configurations shown in the above embodiments are merely examples, and may be combined with other known technologies, or different embodiments may be combined with each other. It is also possible to omit or modify parts of the configurations as long as they do not deviate from the gist of the invention.

[0110] 1 AC power supply, 2 AC / DC converter, 3 DC / AC converter, 4 Load, 6 Control unit, 8 Rotating machine drive device, 9a, 9b DC bus, 20 Rectifier circuit, 41 Motor, 42 Compressor, 60 PS controller, 61 Estimation unit, 210, 211 Current detection unit, 212, 2191a, 2191b Reactor, 213a, 213b Single-phase diode bridge cell, 215, 220a to 220h, 2193a, 2193b Switching element, 216, 216a to 216c Capacitor, 217a to 217c Voltage detection unit, 218, 218a to 218c, 2192a, 2192b Diode, 219 Interleaved cell, 221 Single-phase H-bridge cell, 222, 225 Switching cell, 242 current source, 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, which rectifies the power supply voltage applied from a single-phase AC power supply, A capacitor connected to the DC bus and smoothing the output voltage of the rectifier circuit, A reactor located on the single-phase AC power supply side of the capacitor, A control unit that generates a switching signal for controlling the switching element, A current detection circuit using a shunt resistor connected in series with the switching element, Equipped with, The switching element is positioned on the single-phase AC power supply side of the capacitor. The control unit estimates the power supply current flowing through the reactor when the switching element is off, using the power supply voltage, the inductance value of the reactor, the terminal voltage of the capacitor, and the duty cycle indicating the percentage of time the switching element is turned off during a specified period, and generates the switching signal. AC / DC converter.

2. An AC current transformer, positioned before or after the reactor, for detecting the current flowing through the reactor. Equipped with, The control unit generates the switching signal using the current value detected by the AC current transformer if the current value detected by the AC current transformer is greater than or equal to a defined threshold, and generates the switching signal using the current value flowing through the shunt resistor or the estimated power supply current if the current value detected by the AC current transformer is less than the threshold. The AC-DC converter according to claim 1.

3. The control unit includes a current controller that controls the power supply current of the single-phase AC power supply, and the current controller comprises at least one controller that satisfies the internal model principle for a sine wave. The AC-DC converter according to claim 1.

4. A rotating machine drive device comprising an AC-DC converter according to any one of claims 1 to 3.

5. A refrigeration cycle application device comprising an AC-DC converter according to any one of claims 1 to 3.