AC / DC converter, rotary machine drive and cooling circuit application device

Abstract

An AC-to-DC converter (2) comprises: a rectifier circuit (20) that rectifies the supply voltage provided by an AC source (1), the rectifier circuit (20) comprising a switching element (215); a capacitor (216) that smooths the output voltage of the rectifier circuit (20), the capacitor (216) being connected to a DC bus (9a, 9b); an inductor (212) located closer to the AC supply (1) than the capacitor (216); a current detector (211) that detects the supply current flowing between the AC supply (1) and the rectifier circuit (20); and a control device (6) that generates a switching signal for controlling the switching element (215). The control device (6) generates the switching signal such that one phase of the supply current is changed.

Description

Area

[0001] The present disclosure relates to: an AC-DC converter that converts alternating current into the desired direct current; and a rotary machine drive and a cooling circuit application device that include the AC-DC converter. background

[0002] When DC voltage is derived from an AC power supply, a power factor correction circuit is generally used. The power factor correction circuit controls the bus voltage to maintain a constant level and the supply current to conform to the harmonic standard. A power factor correction circuit and a "simple switching method" (also called a "partial switching method"), which is a type of control method for the power factor correction circuit, are based on a procedure in which the supply voltage, which is the voltage of an AC power supply, is switched at least once per half-cycle. This method is characterized by the ability to control the bus voltage to be lower than a peak value of the supply voltage.However, if the bus voltage is set to a value lower than the peak AC supply voltage using the simple switching method, an operating circuit switches from a boost chopper to a capacitor-input diode rectifier, resulting in a distortion of the supply current. This is a problem inherent in the simple switching method.

[0003] To solve this problem, the conventional technique disclosed in the patent literature 1 below achieves a desired control with respect to whether a combination of reactor capacity and switching time can meet the harmonic standard by repeating the design for each load power. Citation list for patent literature

[0004] Patent literature 1: Japanese patent application no. 2000-125545 Summary of the invention; Problem statement of the invention

[0005] However, since the conventional method described in patent literature 1 is one in which compliance with the harmonic standard is verified by repeated trials, the method suffers from the problem that the number of trials increases exponentially with the number of pulses. Furthermore, the conventional method described in patent literature 1 also suffers from the problem that it is very time-consuming to design the control gain, as the guidelines for the quantitative and unambiguous design of the control gain are not clear.

[0006] The present disclosure was made in consideration of the foregoing, and one objective of the present disclosure is to reduce the time required for interpretation by providing an AC-DC converter that achieves conformity with the harmonic standard without relying on adaptation by trial and error. Means of solving the problem

[0007] To solve the problems described above and achieve the objective, an AC-DC converter according to the present disclosure comprises: a rectifier circuit; a capacitor; an inductor; a current detector; and a control unit. The rectifier circuit includes at least one switching element and rectifies the supply voltage applied by an AC source. The capacitor is connected to a DC bus and smooths the output voltage of the rectifier circuit. The inductor is located closer to the AC supply than the capacitor. The current detector senses the supply current flowing between the AC supply and the rectifier circuit. When generating a switching signal to control the switching element located closer to the AC supply than the capacitor, the control unit generates the switching signal such that the phase of the supply current is changed. Effects of the invention

[0008] The AC-DC converter according to the present disclosure achieves conformity with the harmonic standard without relying on trial-and-error adjustment. Thus, the AC-DC converter according to the present disclosure has the effect of reducing the time required for its construction. Brief description of the drawings Fig. Figure 1 is a block diagram illustrating an exemplary configuration of a rotary machine drive according to a first embodiment. Fig. Figure 2 is a circuit diagram illustrating an exemplary configuration of an AC-DC converter according to the first embodiment. Fig. Figure 3 is a block diagram illustrating an exemplary configuration of a controller according to the first embodiment. Fig. Figure 4 is a block diagram showing an exemplary configuration of a sine wave generator included in the controller according to the first embodiment. Fig. 5 is a diagram showing exemplary operating waveforms that are obtained when the in Fig. The two AC-DC converters shown are operated passively. Fig. Figure 6 is a diagram illustrating exemplary operating waveforms that are obtained when the in Fig. The two AC-DC converters shown are operated with a basic power factor of 1. Fig. Figure 7 is a diagram illustrating exemplary operating waveforms obtained when a phase-shift control is applied to the [unclear text]. Fig. The process is carried out using the AC-DC converter shown in section 2. Fig. Figure 8 is a diagram illustrating an exemplary configuration of a device operated with a cooling circuit according to a second embodiment. Description of the embodiments

[0009] In the following, an AC-DC converter, a lathe driver and a device operated with a cooling circuit according to embodiments of the present disclosure are described in detail with reference to the accompanying drawings. First embodiment.

[0010] Fig. Figure 1 is a block diagram illustrating an exemplary configuration of a rotary machine drive 8 according to a first embodiment. The rotary machine drive 8 is connected to an AC power supply 1 and a load 4, which includes a motor 41. The rotary machine drive 8 includes an AC-to-DC converter 2 and a DC-to-AC converter 3. When the rotary machine drive 8 is used for an air conditioner, the load 4 is a compressor or a fan, and the motor 41 is a compressor motor or a fan motor.

[0011] Fig. Figure 2 is a circuit diagram illustrating an exemplary configuration of the AC-DC converter 2 according to the first embodiment. The AC-DC converter 2 according to the first embodiment comprises as its main components a control unit 6, a rectifier circuit 20, an inductor 212, and a capacitor 216. Furthermore, the AC-DC converter 2 includes a current detector 211 and voltage detectors 217a and 217b as voltage or current sensing means. It should be noted that, where the voltage detectors 217a and 217b are distinguished from one another without reference numerals, voltage detector 217b is referred to as the "first voltage detector" and voltage detector 217a as the "second voltage detector."

[0012] The rectifier circuit 20 comprises: single-phase diode bridge cells 213a and 213b, each comprising four diodes connected in a bridge configuration; and a switching element 215 connected in parallel to both ends of the single-phase diode bridge cell 213b. The single-phase diode bridge cells 213a and 213b are connected in parallel with respect to the AC supply 1. The in Fig. The rectifier circuit 20 shown in Figure 2 is referred to as a "simple switch 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 supply voltage.

[0013] Capacitor 216 is connected between a DC bus 9a and a DC bus 9b. Inductor 212 is located closer to the AC power supply than capacitor 216. Rectifier circuit 20 receives the supply voltage applied by the AC power supply 1 via inductor 212 and rectifies the received supply voltage. Capacitor 216 smooths the output voltage of rectifier circuit 20.

[0014] The voltage detector 217b detects the bus voltage, i.e., the voltage of the DC bus to which the capacitor is connected. The voltage detector 217a detects the supply voltage. The current detector 211 detects the supply current flowing between the AC power supply 1 and the rectifier circuit 20.

[0015] The measured values ​​from voltage detectors 217a and 217b, as well as current detector 211, are each input into control unit 6. Based on these individual measured values, control unit 6 generates a switching signal to control the switching on and off of switching element 215.

[0016] An example of switching element 215 is the insulated-gate bipolar transistor (IGBT) shown in the drawing, but this is not limited to IGBTs. Any element can be used as switching element 215 as long as a switching operation can be performed. Another example of switching element 215 is a metal-oxide-semiconductor field-effect transistor (MOSFET).

[0017] Although the in Fig. While the AC-DC converter 2 shown in Figure 2 is configured as a closed-loop control system, using the respective detection values ​​of the voltage detectors 217a and 217b and the current detector 211, it can also be configured as an open-loop control system, using a setpoint, an estimated value, and the like. In the case where the AC-DC converter 2 is configured as an open-loop control system, it is possible to control the switching element 215 without using the respective detection values ​​of the voltage detectors 217a and 217b and the current detector 211.

[0018] Fig. Figure 3 is a block diagram illustrating an exemplary configuration of the control unit 6 according to the first embodiment. The control unit 6 comprises: a subtractor 611; a voltage regulator 612; a multiplier 613; a subtractor 614; a current control unit 615; a switching signal generator 616; and a sine wave signal generator 617.

[0019] The subtractor 611 generates a voltage deviation, which is the difference between an initial voltage command value and a detection value of the bus voltage detected by the voltage detector 217b. The initial voltage command value is a command value of the bus voltage. The voltage regulator 612 generates an initial current command value using the voltage deviation output by the subtractor 611. The voltage regulator 612 can be configured, for example, as a proportional-integral (PI) controller.

[0020] When the voltage regulator 612 is configured as a PI controller, the transfer function G AVR(s) can be expressed by the following formula (1). Formula 1: GAVR(s)=KpAVR+KiAVRs

[0021] Here, the symbol "AVR" is used in the transfer function G. AVR(s) an abbreviation for “automatic voltage regulator”. Furthermore, in the formula (1) above, the symbol “K” denotes pAVR “the proportional reinforcement, the symbol “K” iAVR “The integral gain and the symbol “s” is a Laplace operator. The proportional gain K pAVR and the integral gain K iAVR The values ​​can be freely determined in the PI controller. It should be noted that the voltage regulator 612 functions as an I-controller with a proportional gain K set to zero. pAVR or as a P-controller with an integral gain K set to zero iAVR can be configured.

[0022] The sine wave generator 617 produces a sine wave signal, which serves as the excitation signal, based on the first voltage command value and a supply voltage sensing value. The multiplier 613 multiplies the first current command value by the sine wave signal. The sine wave signal is a sine wave synchronized with the phase of the supply voltage. The output of the multiplier 613 is fed into the subtractor 614 as the second current setpoint. The subtractor 614 generates a current deviation, which is the difference between the second current setpoint and a supply current sensing value detected by the current detector 211. The current control unit 615 generates a second voltage setpoint using the current deviation output by the subtractor 614. The current control unit 615 can be configured, for example, as a PI controller. The switching signal generator 616 generates a switching signal using the second voltage command value.

[0023] In a case where the current control unit 615 is configured as a PI controller, a transfer function G can be used. ACR(s) can be expressed by the following formula (2). Formula 2: GACR(s)=KpACR+KiACRs

[0024] Here is the symbol “ACR” in the transfer function G. ACR(s) an abbreviation for “automatic current control unit”. Furthermore, in the formula (2) above, the symbol “K” denotes pACR “the proportional reinforcement, the symbol “K” iACR “The integral gain and the symbol “s” is a Laplace operator. The proportional gain K pACR and the integral gain K iACR These values ​​can be freely determined in the PI controller. It should be noted that the current control unit 615 is configured as an I-controller with a proportional gain K set to zero. pACR or as a P-controller with an integral gain K set to zero iACR It may be configured.

[0025] Fig. Figure 4 is a block diagram showing an exemplary configuration of the sine wave generator 617, which is included in the controller 6 according to the first embodiment. The sine wave generator 617 outputs a sine wave that is synchronized with the phase and frequency of the supply voltage. To implement this function, the sine wave generator 617 includes: a phase-locked loop (PLL) computer 6171; a subtractor 6172; a sine wave calculator 6173; and a phase-shift calculator 6174.

[0026] The PLL calculator 6171 generates and outputs a sine wave synchronized with the phase and frequency of the supply voltage. The phase shift calculator 6174 calculates a phase shift based on a sensing value of the supply voltage and the first voltage command value, which is a command value of the bus voltage. The subtractor 6172 calculates a difference between the output of the PLL calculator 6171 and the output of the phase shift magnitude calculator 6174. The sine wave calculator 6173 calculates a sine wave signal using the difference output by the subtractor 6172.

[0027] Next, a method for calculating the magnitude of a phase shift is described with reference to several drawings and mathematical expressions.

[0028] Fig. 5 is a diagram illustrating exemplary operating waveforms that are obtained when the in Fig. The AC-DC converter 2 shown is operated passively. Passive operation refers to operation carried out in a passive mode. Passive mode refers to a mode in which the rectifier circuit 20 operates without switching the switching element 215. In the upper part of Fig. Figure 5 shows a waveform of the absolute value of the supply voltage represented by a dashed line and a waveform of the bus voltage represented by a solid line. In the lower part of Fig. Figure 5 shows a waveform of the supply current represented by a dashed line and a waveform of a fundamental component of the supply current represented by a solid line. The supply current shown in the lower part is a detection waveform of the supply current detected by the current detector 211.

[0029] In passive mode, current flows to excite the inductor 212 when the supply voltage exceeds the bus voltage. A current-flow start phase γ, at which the current begins to flow, corresponds to an intersection point where the supply voltage rises to a voltage equal to the bus voltage and is thus obtained by the following formula (3). Formula 3: γ=sin−1(Vdc2vs)

[0030] In the formula (3) above, V denotes dc the bus voltage and v s The RMS value of the supply voltage. The supply current continues to rise until the supply voltage again exceeds the bus voltage. This intersection point corresponds to a peak value of the supply current. A current peak phase φ, which is the phase of the peak value of the supply current, can be expressed using the following formula (4) based on the peak value of the supply voltage. Formula 4: ϕ=π2−sin−1(Vdc2vs)

[0031] When the supply voltage drops below the bus voltage, the current decreases and eventually becomes zero. Based on the circuit operation described above, the supply voltage has a schematic form, as shown by the line in Fig. 5 shown.

[0032] Furthermore, the fundamental component of the supply voltage during passive operation has a waveform whose phase is delayed relative to the supply voltage, as shown in Fig. Figure 5 illustrates this. Due to the characteristics occurring during passive operation, a low harmonic is superimposed on the power supply current when the basic power factor is set to 1, provided the bus voltage is equal to or less than the peak value of the supply voltage. The reason for this is as follows. First, during passive operation, when the basic power factor is set to 1, it is necessary to switch several times after the zero crossing of the supply voltage. However, this switching control distorts the power supply current. Therefore, if the basic power factor is set to 1 while the bus voltage is equal to or less than the peak value of the supply voltage, the power supply current is distorted, and the power supply is superimposed with a low harmonic.

[0033] Therefore, in the control method described here, instead of setting the fundamental power factor to 1 when the bus voltage is equal to or less than the peak value of the supply voltage, the phase of the sine wave signal that excites the first current command value is controlled so that the phase of the sine wave signal is synchronized with a fundamental phase of the supply current during passive operation. The current distortion caused by the fundamental phase control of the supply current can thus be reduced. In this way, it is possible to suppress a harmonic component that may be present in the supply current when the bus voltage is equal to or less than the peak value of the supply voltage.

[0034] To calculate the phase of the supply current during passive operation, it is conceivable to use a Fourier series expansion, in which a time formula for the supply current during passive operation is established. However, with this method, the point in time at which the current becomes zero cannot be calculated using algebraic operations. Therefore, the calculation of a fundamental frequency can only be performed analytically. Thus, a phase shift magnitude δ is determined approximately here.

[0035] The phase shift magnitude δ is in the lower part of Fig. Figure 5 illustrates this. The phase shift magnitude δ refers to a phase of the peak value of the power supply current based on the peak value of the supply voltage. The current peak value φ described above, however, is in the upper part of Fig. Figure 5 illustrates this. The current peak value φ refers to a phase of the peak current of the power supply during passive operation. Both the phase shift magnitude δ and the current peak phase φ are based on the peak value of the supply voltage. Furthermore, both are, as shown in Fig. 5 are shown, close together and have similar values.

[0036] Therefore, it is assumed here that the phase shift magnitude δ is essentially equal to the current peak phase φ, and the phase shift magnitude δ is defined by the following formula (5). Formula 5: δ≈π2−sin−1(Vdc2vs)

[0037] It should be noted that the above formula (5) is an example and the phase shift magnitude δ in the present description is not limited to the above formula (5).

[0038] The phase shift calculator 6174 outputs the phase shift amount δ generated on the basis of the above formula (5) to the subtractor 6172. If θ vs The sine phase, which is output by the PLL computer 6171, is called “θ vs -δ“ is entered into the sine wave calculator 6173. Therefore, a sine signal f, expressed by the formula (6) below, is output by the sine wave calculator 6173. Formula 6: f=sin(θvs−δ)

[0039] The sine wave f is a signal that triggers the first current command value. If the phase of the sine wave f is shifted, the phase of the supply current is also shifted. This control is accordingly referred to here as "phase shift control".

[0040] Fig. Figure 6 is a diagram illustrating exemplary operating waveforms that are obtained when the in Fig. The two AC-DC converters shown are operated with a basic power factor of 1. In the upper part of Fig. Figure 6 shows a waveform of the absolute value of the supply voltage represented by a dashed line and a waveform of the bus voltage represented by a solid line. In the lower part of Fig. Figure 6 shows a waveform of the supply current represented by a solid line and a waveform of the fundamental wave component of the supply current represented by a dashed line.

[0041] As seen through the continuous waveform in the lower part of Fig. When 6 is displayed, the switching control of switching element 215 focuses on a period that begins when the supply voltage passes a zero crossing point and ends when the absolute value of the supply voltage reaches its peak value. That is, if the basic power factor of the supply current is set to 1 without using phase shift control, the switching control of switching element 215 focuses on a portion of the period, resulting in a distortion of the supply current.

[0042] Fig. Figure 7 is a diagram illustrating exemplary operating waveforms obtained when the phase shift control is applied to the [unclear text]. Fig. The AC-DC converter 2 shown in the diagram is used. In the upper part of Fig. Figure 7 shows a waveform of the absolute value of the supply voltage represented by a dashed line and a waveform of the bus voltage represented by a solid line. In the lower part of Fig. Figure 7 shows a waveform of the supply current represented by a solid line.

[0043] If you look at the waveform in the lower part of Fig. 7, while a slight change in the current can be observed, the waveform of the supply current itself changes according to the waveform of the fundamental frequency of the supply current. Therefore, when the AC-DC converter 2 is operated using the phase-shift control described in this description, the current can be controlled sinusoidally. By using the phase-shift control described in this description, it is therefore possible to operate the AC-DC converter 2 in accordance with the harmonic standard without having to rely on a trial-and-error setting, where compliance with the harmonic standard is verified by repeated attempts.

[0044] As described above, the AC-to-DC converter according to the first embodiment comprises: a rectifier circuit that rectifies the supply voltage applied by an AC power supply; a capacitor that smooths the output voltage of the rectifier circuit; an inductor located closer to the AC power supply than the capacitor; and a current detector that detects the supply current flowing between the AC power supply and the rectifier circuit. The rectifier circuit includes at least one switching element located closer to the AC power supply than the capacitor. When generating a switching signal to control the switching element, the control unit generates the switching signal such that the phase of the supply current is changed. According to the AC-to-DC converter of the first embodiment, the supply current can be controlled sinusoidally.This allows the harmonic components in the current flowing between the AC supply and the rectifier circuit to conform to the harmonic standard without requiring trial-and-error adjustment. Furthermore, according to the AC-DC converter of the first embodiment, it is possible to comply with the harmonic standard while simultaneously improving the input power factor, even under the operating condition that the bus voltage is equal to or less than the peak absolute value of the supply voltage.

[0045] To achieve the aforementioned function, the AC-DC converter according to the first embodiment includes a current detector that senses the power supply current, and the controller generates a switching signal such that one phase of the power supply current is changed based on a fundamental waveform of the power supply current, which is detected when the switching element is off, to cause the rectifier circuit to operate passively. By controlling the switching element of the rectifier circuit using the switching signal generated in this way, it is possible to control the current sinusoidally. Therefore, even under the operating condition that the bus voltage is equal to or less than the peak absolute value of the supply voltage, it is possible to maintain the harmonic standard while simultaneously improving the input power factor.It should be noted that it is possible to generate such a switching signal by changing the phase of the supply current according to a magnitude ratio between a bus voltage detection value captured by the first voltage detector and a supply voltage detection value captured by the second voltage detector. Second embodiment.

[0046] Fig. Figure 8 is a diagram illustrating an exemplary configuration of a refrigeration cycle application device 900 according to a second embodiment. The refrigeration cycle application device 900 according to the second embodiment comprises the rotary machine drive 8 described in the first embodiment. The refrigeration cycle application device 900 according to the second embodiment can be applied to products with a refrigeration cycle, such as an air conditioner, a refrigerator, a freezer, and a heat pump water heater.

[0047] The refrigeration cycle application device 900 comprises: a compressor 42 with the motor 41 according to the first embodiment; a four-way valve 902; an internal heat exchanger 906; an expansion valve 908; and an external heat exchanger 910, which are installed via a refrigerant line 912. The compressor 42 comprises the motor 41 according to the first embodiment. Inside the compressor 42 are the compression mechanism 904, which compresses a refrigerant, and the motor 41, which actuates the compression mechanism 904. The device 900, equipped with a cooling circuit, can perform heating or cooling operation depending on the switching operation of the four-way valve 902.

[0048] The compression mechanism 904 is driven by the motor 41, which is subject to variable speed control. During heating operation, the refrigerant is pressurized by the compression mechanism 904 and discharged from it, passing through the four-way valve 902, the internal heat exchanger 906, the expansion valve 908, the external heat exchanger 910, and back to the four-way valve 902, before returning to the compression mechanism 904, as indicated by the solid arrows. During cooling operation, the refrigerant is pressurized by the compression mechanism 904 and discharged from it, passing through the four-way valve 902, the external heat exchanger 910, the expansion valve 908, the internal heat exchanger 906, and back to the four-way valve 902, before returning to the compression mechanism 904, as indicated by the dashed arrows.During heating operation, the internal heat exchanger 906 acts as a condenser to release heat, and the external heat exchanger 910 acts as an evaporator to absorb heat. During cooling operation, the external heat exchanger 910 acts as a condenser to release heat, and the internal heat exchanger 906 acts as an evaporator to absorb heat. The expansion valve 908 decompresses and expands the refrigerant.

[0049] The configurations shown in the embodiments above are examples, and it is possible to combine the configurations with another known technique or to combine the embodiments with one another, and it is also possible to partially omit or modify the configurations without deviating from the scope of this disclosure. For example, the control method described above is also applicable to a DC-AC converter. List of reference symbols 1 AC power supply; 2 AC-DC converters; 3 DC-AC converters; 4 Last; 6 Control; 8 Rotary machine drive; 9a, 9b DC bus; 20 Rectifier circuit; 41 Engine; 42 Compressor; 211 Current detector; 212 Inductance; 213a, 213b Single-phase diode bridge cell; 215 Switching element; 216 Capacitor; 217a, 217b Voltage detector; 225 switching cell; 611, 614, 6172 Subtractors; 612 Voltage regulators; 613 multiplier; 615 Power control unit; 616 Switching signal generator; 617 Sine wave generator; 900 cold cycle application equipment; 902 Four-way valve; 904 Compression mechanism; 906 Internal heat exchangers; 908 Expansion valve; 910 External heat exchanger; 912 Refrigerant line; 6171 PLL calculator; 6173 Sine wave calculator; 6174 Phase shift calculator. QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] JP 2000-125545

[0004]

Claims

[1] An AC-DC converter comprising: a rectifier circuit configured to rectify the supply voltage applied by an AC power supply, wherein the rectifier circuit comprises at least one switching element; a capacitor configured to smooth the output voltage of the rectifier circuit, with the capacitor connected to a DC bus; an inductor that is located closer to the AC power supply than the capacitor; a current detector configured to detect the supply current flowing between the AC power supply and the rectifier circuit; and a control unit configured to generate a switching signal to control the switching element, wherein the switching element is located closer to the AC power supply than the capacitor and the control unit is configured to generate the switching signal in such a way that the phase of the supply current changes. [2] AC-DC converter according to claim 1, wherein the control unit is configured to generate the switching signal such that the phase of the supply current is changed based on a fundamental wave of the supply current which is detected when the switching element is off, in order to cause the rectifier circuit to operate passively. [3] AC-DC converter according to claim 2, comprising: a first voltage detector configured to detect the bus voltage, which is the voltage of the DC bus; and a second voltage detector configured to detect the supply voltage, wherein the control unit is configured to generate the switching signal such that the phase of the supply current is changed according to a size ratio between a detected value of the bus voltage and a detected value of the supply voltage. [4] A rotary machine drive comprising the AC-DC converter according to any one of claims 1 to 3. [5] A device operated with a cooling circuit, comprising the AC-DC converter according to any one of claims 1 to 3.

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