Ac / DC conversion device, rotary machine drive device, and apparatus for application in refrigeration cycle

Abstract

An AC / DC conversion device (2) includes: a rectifier circuit (20) that includes a switching element (215) and rectifies a power supply voltage applied from an AC power supply (1); a capacitor (216) that is connected to DC buses (9a, 9b) and smooths the output voltage of the rectifier circuit (20); a reactor (212) that is disposed more towards the AC power supply (1) side than the capacitor (216); a current detection unit (211) that detects a power supply current flowing between the AC power supply (1) and the rectifier circuit (20); and a control unit (6) that generates a switching signal for controlling the switching element (215). The control unit (6) generates the switching signal to change the phase of the power supply current.

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 specifications. 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 checking whether compliance with harmonic standard values ​​can be achieved through repeated trials, which has the problem that the number of trials increases exponentially as the number of pulses increases.Furthermore, there is no clear guideline for quantitatively and uniquely designing control gains, which has the problem that it takes a long time to complete the design.

[0006] Therefore, instead of a trial-and-error approach, a control method that feeds back current and voltage has been considered. For example, a PS (Proportional Sinusoidal) controller is devised, in which a P (Proportional) controller and an S (Sinusoidal transfer function) controller that has good tracking ability for sinusoidal command are connected in parallel. This method eliminates the need for a trial-and-error approach, making it possible to shorten the time required for design work.

[0007] On the other hand, in order to reduce a specific order component using a PS controller, an S controller must be provided in parallel for each specific order component. Furthermore, the power supply harmonic standards set standard values ​​for each order component from the 2nd to the 40th order of the power supply frequency. Therefore, when there are many order components to be reduced, the number of S controllers connected in parallel increases, resulting in another problem of a very large computational load.

[0008] The present disclosure has been made in consideration of the above, and aims to obtain an AC-DC conversion device that can comply with harmonic standard values ​​while shortening the time required for design work and suppressing an increase in calculation load.

[0009] 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, a current detection unit, 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. The current detection unit detects a power supply current flowing between the AC power supply and the rectifier circuit. When generating a switching signal for controlling the switching element arranged closer to the AC power supply than the capacitor, the control unit generates the switching signal so as to change the phase of the power supply current.

[0010] The AC-DC converter according to the present disclosure has the effect of being able to comply with harmonic standard values ​​while shortening the time required for design work and suppressing an increase in the calculation load.

[0011] 2 is operated with a fundamental wave power factor of 1. A diagram for explaining Newton's method used in embodiment 1. A diagram showing an example of a curve representing a current conduction end phase used in phase shift control of embodiment 1. A diagram showing an example of an operation waveform when phase shift control is not performed on the AC-DC converter shown in FIG. 2. A diagram showing an example of an operation waveform when phase shift control is performed on the AC-DC converter shown in FIG. 2. A diagram showing an example of an operation waveform when phase shift control is performed on the AC-DC converter shown in FIG. 2. A diagram showing an example of a configuration of a sine wave signal generator provided in a control unit according to embodiment 2. FIG. 13 is a block diagram showing a configuration example of an AC-DC converter according to embodiment 14; FIG. 14 is a block diagram showing a configuration example of an AC-DC converter according to embodiment 15; FIG. 15 is a block diagram showing a configuration example of an AC-DC converter according to embodiment 16;

[0012] 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.

[0013] 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 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.

[0014] 2 is a diagram showing an example of the configuration of an 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."

[0015] 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 constitute a switching cell 225. The switching element 215 performs a switching operation at least once per half cycle of the power supply voltage.

[0016] 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 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 smoothes the output voltage of the rectifier circuit 20.

[0017] The voltage detection unit 217b detects the bus voltage, which is the voltage of the DC buses 9a, 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. The power supply current is also the current flowing through the reactor 212, and is sometimes called the "reactor current."

[0018] 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.

[0019] 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).

[0020] 2 is configured as a closed loop using the detected values ​​of the voltage detectors 217a, 217b and the current detector 211, 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 211.

[0021] 3 is a block diagram showing an example configuration of the control unit 6 according to embodiment 1. The control unit 6 includes a subtractor 611, a voltage controller 612, a multiplier 613, a subtractor 614, a current controller 615, a switching signal generator 616, and a sine wave signal generator 617.

[0022] The subtractor 611 generates a voltage deviation, which is the difference between the first voltage command value and the bus voltage detected by the voltage detection unit 217b. The first voltage command value is a command value for the bus voltage. The voltage controller 612 generates a first current command value using the voltage deviation output from the subtractor 611. The voltage controller 612 can be configured, for example, by a PI (Proportional Integral) controller.

[0023] The transfer function G when the voltage controller 612 is configured as a PI controller ＡＶＲ（ｓ） can be expressed by the following equation (1).

[0024]

[0025] Here, the transfer function G ＡＶＲ（ｓ） "AVR" in the above is an abbreviation for "Automatic Voltage Regulator." Also, in the above formula (1), K ｐＡＶＲ is the proportional gain, and K ｉＡＶＲ is the integral gain and s is the Laplace operator. In the PI controller, the proportional gain K ｐＡＶＲ and integral gain K ｉＡＶＲ can be determined arbitrarily. ｐＡＶＲ may be set to zero and configured as an I (Integral) controller, or an integral gain K ｉＡＶＲ may be set to zero and configured as a P controller.

[0026] The sine wave signal generator 617 generates a sine wave signal as an excitation signal based on the first voltage command value and the detected value of the power supply voltage. 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 and frequency of the power supply voltage. The output of the multiplier 613 is input to the subtractor 614 as a second current command value. The subtractor 614 generates a current deviation, which is the difference between the second current command value and the detected value of the power supply current detected by the current detection unit 211. The current controller 615 generates a second voltage command value using the current deviation output from the subtractor 614. The current controller 615 can be configured, for example, by a PI controller. The switching signal generator 616 generates a switching signal using the second voltage command value.

[0027] The transfer function G when the current controller 615 is configured as a PI controller ＡＣＲ（ｓ） can be expressed by the following equation (2).

[0028]

[0029] Here, the transfer function G ＡＣＲ（ｓ） "ACR" in the above expression is an abbreviation for "Automatic Current Regulator." ｐＡＣＲ is the proportional gain, and K ｉＡＣＲ is the integral gain and s is the Laplace operator. In the PI controller, the proportional gain K ｐＡＣＲ and integral gain K ｉＡＣＲ can be determined arbitrarily. ｐＡＣＲ may be set to zero and configured as an I controller, or the integral gain K ｉＡＣＲ may be set to zero and configured as a P controller.

[0030] 4 is a block diagram showing an example of the configuration of the sine wave signal generator 617 provided in the control unit 6 according to embodiment 1. The sine wave signal generator 617 outputs a sine wave synchronized with the phase and frequency of the power supply voltage. To achieve this function, the sine wave signal generator 617 includes a PLL (Phase Locked Loop) calculator 6171, a subtractor 6172, a sine wave calculator 6173, and a phase shift amount calculator 6174.

[0031] The PLL calculator 6171 generates and outputs a sine wave phase synchronized with the phase and frequency of the power supply voltage. The phase shift amount calculator 6174 calculates a phase shift amount based on the detected value of the power supply voltage and a first voltage command value which is a command value for the bus voltage. The subtractor 6172 calculates the difference between the output of the PLL calculator 6171 and the output of the phase shift amount calculator 6174. The sine wave calculator 6173 calculates a sine wave signal using the difference output from the subtractor 6172.

[0032] The present invention is characterized by the method of calculating the phase shift amount output by the phase shift amount calculator 6174. The details of the method of calculating the phase shift amount will be described later.

[0033] 5 is a diagram showing an example of operating waveforms when the AC-DC converter 2 shown in FIG. 2 is operated passively. Passive operation refers to operation in passive mode. Passive mode is a mode in which the rectifier circuit 20 operates without switching the switching element 215. In the upper part of FIG. 5, the waveform of the absolute value of the power supply voltage is shown by a dashed line, and the waveform of the bus voltage is shown by a solid line. In the lower part of FIG. 5, the waveform of the power supply current is shown by a dashed line, and the waveform of the fundamental wave component (command value) of the power supply current is shown by a solid line. The power supply current shown in the lower part is the detected waveform of the power supply current detected by the current detection unit 211.

[0034] In passive mode, when the power supply voltage exceeds the bus voltage, a power supply current flows and excites the reactor 212. Figure 5 shows how the power supply current starts to flow at time t1. Time t1 is the time of intersection where the power supply voltage rises and becomes equal to the bus voltage. In this paper, the phase at which the power supply current starts to flow is called the "conduction start phase" and is represented by "α". This conduction start phase α can be calculated using the following equation (3):

[0035]

[0036] In the above formula (3), V ｄｃ is the bus voltage, and V ｓ is the effective value of the power supply voltage. The power supply current continues to increase until time t2 when the power supply voltage and the bus voltage cross again, and this intersection point is the peak value of the power supply current.

[0037] When the power supply voltage falls below the bus voltage, the power supply current decreases and becomes zero at time t3. In this paper, the phase at which the power supply current stops flowing after it has started is called the "conduction end phase" and is represented by "β". Due to the circuit operation described above, the power supply current takes on an approximate shape as shown by the dashed line in the lower part of Figure 5. Both the conduction start phase α and the conduction end phase β are based on the zero-cross phase of the power supply voltage. For convenience, in this paper, the conduction start phase α may be called the "first phase" and the conduction end phase β may be called the "second phase".

[0038] During passive operation, the fundamental component of the power supply current has a waveform that lags in phase with the power supply voltage, as shown in Figure 5. Due to this characteristic during passive operation, if you try to achieve a fundamental power factor of 1 when the bus voltage is below the peak value of the power supply voltage, low-order harmonics will be superimposed on the power supply current. The reason for this is as follows. First, if you try to achieve a fundamental power factor of 1 during passive operation, multiple switching operations are required after the zero crossing of the power supply voltage. However, this switching control distorts the power supply current. Therefore, if you try to achieve a fundamental power factor of 1 when the bus voltage is below the peak value of the power supply voltage, the power supply current will be distorted and low-order harmonics will be superimposed on the power supply current. Figure 6 shows an example of a specific operating waveform.

[0039] Fig. 6 is a diagram showing an example of operating waveforms when the AC-DC converter 2 shown in Fig. 2 is operated with a fundamental power factor of 1. In the upper part of Fig. 6, the waveform of the absolute value of the power supply voltage is shown by a dashed line, and the waveform of the bus voltage is shown by a solid line. In the lower part of Fig. 6, the waveform of the power supply current is shown by a solid line, and the waveform of the fundamental wave component (command value) of the power supply current is shown by a dashed line.

[0040] 6, the switching control for the switching element 215 is concentrated in the period from when the power supply voltage passes the zero crossing point until before the absolute value of the power supply voltage reaches its peak value. In other words, if the fundamental power factor of the power supply current is set to 1 without taking the phase of the power supply current into consideration, the switching control for the switching element 215 will be concentrated in a certain period, resulting in distortion of the power supply current.

[0041] Therefore, in the control method described in this paper, when the bus voltage is below the peak value of the power supply voltage, instead of simply setting the fundamental power factor to 1, the phase of the sinusoidal signal that oscillates the first current command value is shifted to synchronize it with the fundamental phase of the power supply current during passive operation. This control is called "phase shift control" in this paper. Phase shift control can reduce current distortion caused by fundamental control of the power supply current, making it possible to suppress harmonic components that may be contained in the power supply current when the bus voltage is below the peak value of the power supply voltage.

[0042] In phase shift control, it is necessary to calculate the amount of phase shift. In this paper, in order to improve the control accuracy of phase shift control, a method for calculating the amount of phase shift with high accuracy, rather than calculating it approximately, is disclosed. Below, the method for calculating the amount of phase shift is explained using several diagrams and formulas.

[0043] First, as a prerequisite, the power supply voltage v ｓ is defined by the following equation (4).

[0044]

[0045] In the above formula (1), "V ｓ " is the power supply voltage V ｓ is the effective value of the power supply voltage v ｓ is the angular frequency of

[0046] Next, when one period of the power supply voltage is defined as "T", the period from time t = 0 to T / 2, which is half the period of the power supply voltage in Figure 5, is divided into the following three periods depending on the value of the current phase θ, which is the phase of the power supply current.

[0047] Section 1: 0≦θ≦α (0≦t≦t1) Section 2: α≦θ≦β (t1≦t≦t3) Section 3: β≦θ≦180° (t3≦t≦T / 2)

[0048] Hereinafter, the power supply currents flowing in Section 1, Section 2, and Section 3 are referred to as "i Ｌ１ ", "i Ｌ２ " and "i Ｌ３ " is written as

[0049] In section 1, the power supply voltage v ｓ is the bus voltage V ｄｃ Therefore, the power supply current i Ｌ１ is expressed as the following equation (5).

[0050]

[0051] In the section 2, the diode in the single-phase diode bridge cell 213a is in a diode rectification mode in which current flows. Ｌ The differential equation for can be expressed by the following equation (6).

[0052]

[0053] In the above equation (6), “L” is the inductance of the reactor 212 .

[0054] In the above equation (6), if the time t is any time between t1 and t3, and both sides are integrated with respect to time, the following equation (7) is obtained. Note that since the initial value is zero, it is not necessary to consider the initial value.

[0055]

[0056] When the above equation (7) is converted into a phase, the power supply current i flowing in section 2 is Ｌ２ can be expressed by the following equation (8).

[0057]

[0058] In section 3, the current is blocked by the diode of the single-phase diode bridge cell 213a. Therefore, the power supply current i Ｌ３ is expressed as the following equation (9).

[0059]

[0060] Next, using the above equations (5), (8), and (9), the power supply current i Ｌ The fundamental wave component and its phase are calculated by Fourier series expansion. The Fourier series expansion calculates the sine wave component (i Ｌ１ｓｉｎ , i Ｌ２ｓｉｎ , i Ｌ３ｓｉｎ ) and the cosine wave component (i Ｌ１ｃｏｓ , i Ｌ２ｃｏｓ , i Ｌ３ｃｏｓ ) can be derived by calculating each of

[0061] <Section 1>

[0062] <Section 2>

[0063] <Section 3>

[0064] From the above equations (10) to (15), it is clear that only section 2 needs to be considered. Ｌ２ Fundamental wave component i Ｌ２ｓｉｎ , i Ｌ２ｃｏｓ When a Fourier series expansion is performed on , the following equations (16) and (17) are obtained.

[0065]

[0066] Therefore, from the above equations (16) and (17), the power supply current i Ｌ２ The amplitude of the fundamental component i １ｆＡｍｐ and the phase δ can be expressed by the following equations (18) and (19), respectively.

[0067]

[0068] To perform phase shift control precisely, the phase δ shown in equation (19) can be used. That is, the phase δ means the phase shift amount in phase shift control. Therefore, in the following description, "phase δ" will also be referred to as "phase shift amount δ" as appropriate. In this paper, the phase shift amount δ is treated as meaning a delayed phase, and therefore a minus sign is added to the right side of equation (19).

[0069] As is clear from equations (16) and (17), the phase shift amount δ is calculated using the power supply voltage v ｓ and bus voltage V ｄｃ The value of the conduction start phase α, which is the intersection of Ｌ The value of the conduction end phase β at which the conduction start phase α is zero is required. The conduction start phase α can be calculated using the above-mentioned equation (3).

[0070] On the other hand, the power supply current i Ｌ The conduction end phase β, where becomes zero, cannot be calculated by algebraic calculation. Therefore, this paper illustrates a method for calculating the conduction end phase β using Newton's method. Note that the use of Newton's method is just one example, and it goes without saying that other numerical analysis methods can be used instead of Newton's method.

[0071] 7 is a diagram illustrating the Newton method used in the first embodiment. FIG. 7 shows an arbitrary function f(x) and a coordinate (x １ , f(x １ The line f'(x) is a tangent to the point on the x-y plane. The point where the line f'(x) intersects with the x-axis is called the "x ２ ". Also, x １ and x ２ The difference between the two, that is, the difference in the x-axis direction, is "Δx", and the y-coordinate f(x １ The difference in the y-axis direction at the coordinate (x １ , f(x １ )) is the differential coefficient f'(x １ ), the relationship of the following equation (20) holds.

[0072]

[0073] If the above formula (20) is expressed as a recurrence formula, it becomes the following formula (21).

[0074]

[0075] When Newton's method is applied to this case, the phase θ ｎ In the above equation (8), the power supply current i Ｌ２ It is sufficient to iteratively find the conditions under which asymptotically approaches zero.

[0076]

[0077] An example of the flow end phase β determined as above is shown in the following equation (23).

[0078]

[0079] The above equation (23) is calculated by using the Newton method to calculate the conduction end phase β for a plurality of output voltage values, and the conduction end phase β and the voltage ratio V ｒ The approximate formula is obtained from the relationship between the voltage ratio V ｒ is the bus voltage V ｄｃ power supply voltage V ｓ The effective value V ｓ The normalized value, i.e., the bus voltage V ｄｃ and power supply voltage V ｓ The effective value Vｓ As a ratio to V ｒ =V ｄｃ / V ｓ The above equation (23) can be expressed as shown in Fig. 8. That is, Fig. 8 is a diagram showing an example of a curve representing the current conduction end phase β used in the phase shift control of the first embodiment.

[0080] The above equation (23) is based on the power supply voltage v ｓ and the inductance L of the reactor 212. Therefore, this equation (23) can be used even when the circuit parameters of the AC-DC converter 2 are changed. This can also be seen from the fact that the angular frequency ω and the inductance L are not included in the above equation (22). Incidentally, the angular frequency ω and the inductance L are not included in the equation (3) that represents the conduction start phase α. From this, it can be seen that the power supply current i Ｌ The phase where is zero is the power supply voltage v ｓ and the inductance L of the reactor 212, and the voltage ratio V ｒ It can be said that it is a physical quantity whose properties change depending on the

[0081] Returning to the explanation of Fig. 4, the phase shift amount calculator 6174 calculates the phase shift amount δ based on the above equation (19). The phase shift amount calculator 6174 outputs the calculated phase shift amount δ to the subtractor 6172. The sine wave phase output from the PLL calculator 6171 is calculated as θ ｖｓ is input to the sine wave calculator 6173. ｖｓ −δ″ is input. Therefore, the sine wave calculator 6173 outputs a sine wave signal f expressed by the following equation (24).

[0082]

[0083] The sine wave signal f is a signal that excites the first current command value, and the power supply current i Ｌ The phase of the signal is also shifted.

[0084] FIG. 9 is a diagram showing an example of operating waveforms when phase shift control is not performed on the AC-DC converter 2 shown in FIG. 2 . In contrast, FIG. 10 is a diagram showing an example of operating waveforms when phase shift control is performed on the AC-DC converter 2 shown in FIG. 2 . In FIGS. 9 and 10 , the waveform of the power supply current is shown by a solid line, and the waveform of the fundamental wave component (command value) of the power supply current is shown by a dashed line. The power factor of the power supply current waveform shown in FIG. 9 is 0.988, and the THD (Total Harmonic Distortion) of the power supply current waveform is 15.6%. The power factor of the power supply current waveform shown in FIG. 10 is 0.918, and the THD of the power supply current waveform is 4.60%. THD is defined by the following equation (25):

[0085]

[0086] I １ is the power supply current i Ｌ is the fundamental component of I ２ , I ３ , I ４ , I ５ , ... are the power supply currents i Ｌ These are second and higher harmonic components in the frequency domain.

[0087] 9 and 10, the power factor value in FIG. 9 is closer to 1. However, in FIG. 9, the power supply current i Ｌ is the power supply current i Ｌ The fundamental wave component of the power supply current i Ｌ In contrast, the waveform of the power supply current i Ｌ The waveform itself is the power supply current i Ｌ That is, if the AC-DC converter 2 is operated using the phase shift control of this paper, the power supply current i Ｌ Therefore, by using the phase shift control of this paper, it is possible to operate the AC-DC converter 2 so as to comply with the harmonic standard values ​​without relying on trial and error adjustments that are performed repeatedly to confirm whether or not compliance with the harmonic standard values ​​is possible.

[0088] 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, a reactor that is disposed closer to the AC power supply than the capacitor, and a current detection unit that detects a power supply current flowing between the AC power supply and the rectifier circuit. The rectifier circuit has at least one switching element that is disposed 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 as to change the phase of the power supply current. The AC-DC converter according to the first embodiment can control the power supply current to a sinusoidal waveform. This enables harmonic components contained in the power supply current flowing between the AC power supply and the rectifier circuit to comply with harmonic specifications without relying on trial-and-error adjustment. Furthermore, the AC-DC converter according to the first embodiment can comply with harmonic specifications even under operating conditions in which the bus voltage is equal to or lower than the peak absolute value of the power supply voltage.

[0089] To achieve the above functions, the AC-DC converter according to the first embodiment includes a current detector that detects a power supply current, and a controller that generates a switching signal to change the phase of the power supply current based on the fundamental wave of the power supply current detected when the switching elements are turned off and the rectifier circuit is in passive operation. By controlling the switching elements of the rectifier circuit using the switching signal generated in this manner, the power supply current can be controlled to a sinusoidal waveform, thereby complying with harmonic standards even under operating conditions where the bus voltage is equal to or less than the peak absolute value of the power supply voltage. The switching signal can be generated by changing the phase of the power supply current depending on the magnitude relationship between the bus voltage detected by the first voltage detector and the power supply voltage detected by the second voltage detector.

[0090] Furthermore, in the AC-DC converter according to the first embodiment, the control unit calculates a phase shift amount based on a first phase at which the power supply current starts to flow when the rectifier circuit is operated passively and a second phase at which the power supply current stops flowing after the power supply current has been flowing. The control unit generates a switching signal to change the phase of the power supply current using the calculated phase shift amount. The accuracy of the phase shift control depends on the accuracy of the first and second phases. In the AC-DC converter according to the first embodiment, the values ​​of the first and second phases can be accurately determined, thereby improving the accuracy of the phase shift control.

[0091] Embodiment 2 In the first embodiment, a method for calculating the conduction end phase β used in the phase shift control using the Newton method has been described. In the second embodiment, a method for calculating the conduction end phase β using the hill-climbing method instead of the Newton method will be described. Note that the use of the hill-climbing method is just one example, and it goes without saying that other optimization methods may be used instead of the hill-climbing method.

[0092] 11 is a block diagram showing an example of the configuration of a sine wave signal generator 617 provided in the control unit 6 according to embodiment 2. Note that the configuration other than the sine wave signal generator 617 is the same as or equivalent to that of embodiment 1.

[0093] 11 and the sine wave signal generator 617 shown in FIG. 4 are different in terms of the input signal to the phase shift amount calculator 6174. In the configuration shown in FIG. 4, the phase shift amount calculator 6174 receives the power supply voltage v ｓ and bus voltage V ｄｃ In the configuration shown in FIG. 11, the phase shift amount calculator 6174 receives the command value of the power supply voltage v ｓ That is, in the AC / DC converter 2 according to the second embodiment, the phase shift amount calculator 6174 calculates the power supply voltage v ｓ The phase shift amount δ is calculated based on the above.

[0094] Specifically, the phase shift amount calculator 6174 calculates the power supply voltage v ｓ is expanded into a Fourier series to calculate the THD defined by the following equation (26).

[0095]

[0096] E １ is the power supply voltage V ｓ is the fundamental wave component of E ２ , E ３ , E ４ , E ５ , ... are the power supply voltages v ｓ The phase shift amount calculator 6174 uses a hill-climbing method to calculate the phase shift amount δ using the THD as an evaluation function. The THD is calculated by multiplying the power supply voltage v ｓ Therefore, if the THD is used as an evaluation function, it is possible to calculate the optimum phase shift amount δ. Note that the THD in equation (25) may be used instead of the THD in equation (26). The THD in equation (25) is calculated by multiplying the power supply current i Ｌ Instead of these THDs, the power supply voltage v ｓ or power supply current i Ｌ The odd-order harmonic components (particularly, the third-order harmonic component and the fifth-order harmonic component) included in the above equation may be used as the evaluation function.

[0097] As described above, in the AC-DC converter according to the second embodiment, the control unit calculates the amount of phase shift based on the first phase at which the power supply current starts to flow when the rectifier circuit is operated passively and the second phase at which the power supply current stops flowing after the power supply current has been flowing. The control unit according to the second embodiment calculates the second phase using an optimization method. Although the accuracy of the phase shift control depends on the accuracy of the first and second phases, the value of the second phase can be accurately determined even using the optimization method. Therefore, the accuracy of the phase shift control can be improved in the AC-DC converter according to the second embodiment as well.

[0098] Embodiment 3 In embodiment 3, a different example of the AC-DC converter 2 including the control unit 6 described in embodiment 1 or embodiment 2 will be described. Note that components having the same or equivalent functions as those 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.

[0099] Fig. 12 is a diagram showing a configuration example of an AC-DC converter 2 according to embodiment 3. 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.

[0100] The control unit 6 generates switching signals to drive the four switching elements 220a, 220b, 220c, and 220d using the control method described in embodiment 1 or embodiment 2. As a result, the AC-DC converter 2 shown in FIG. 12 can also achieve the same effects as those of embodiment 1 or embodiment 2.

[0101] 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.

[0102] Embodiment 4 In embodiment 4, a different example of the AC-DC converter 2 including the control unit 6 described in embodiment 1 or embodiment 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.

[0103] FIG. 13 is a diagram illustrating a configuration example of an AC-DC converter 2 according to a fourth 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 therefore further description thereof will be omitted here.

[0104] The control unit 6 generates switching signals to drive the two switching elements 220c and 220d using the control method described in embodiment 1 or embodiment 2. As a result, the AC-DC converter 2 shown in Fig. 13 can also achieve the same effects as those of embodiment 1 or embodiment 2.

[0105] 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.

[0106] Embodiment 5 In embodiment 5, a different example of the AC-DC converter 2 including the control unit 6 described in embodiment 1 or embodiment 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.

[0107] FIG. 14 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. 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. 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.

[0108] The control unit 6 generates switching signals to drive the two switching elements 220b and 220d using the control method described in embodiment 1 or embodiment 2. As a result, the AC-DC converter 2 shown in Fig. 14 can also achieve the same effects as those of embodiment 1 or embodiment 2.

[0109] 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.

[0110] Sixth Embodiment In a sixth embodiment, a different example of the AC-DC converter 2 including the control unit 6 described in the first or second embodiment will be described. Components having the same or equivalent functions as those of the AC-DC converter 2 described in the first or second embodiment will be denoted by the same reference numerals, and overlapping descriptions will be omitted.

[0111] 15 is a diagram showing a configuration example of an AC-DC converter 2 according to a sixth 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 detector 217c. The voltage detector 217c may be provided outside the rectifier circuit 20.

[0112] 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.

[0113] The control unit 6 generates switching signals to drive the four switching elements 220a, 220b, 220c, and 220d using the control method described in embodiment 1 or embodiment 2. As a result, the AC-DC converter 2 shown in FIG. 15 can also achieve the same effects as those of embodiment 1 or embodiment 2.

[0114] 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.

[0115] Embodiment 7 In embodiment 7, a different example of the AC-DC converter 2 including the control unit 6 described in embodiment 1 or embodiment 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.

[0116] 16 is a diagram illustrating a configuration example of an AC-DC converter 2 according to a seventh 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.

[0117] 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.

[0118] 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.

[0119] The control unit 6 generates switching signals to drive the six switching elements 220b, 220d, 220e, 220f, 220g, and 220h using the control method described in embodiment 1 or embodiment 2. As a result, the AC-DC converter 2 shown in FIG. 16 can also achieve the same effects as those of embodiment 1 or embodiment 2.

[0120] 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.

[0121] Embodiment 8 In embodiment 8, a different example of the AC-DC converter 2 including the control unit 6 described in embodiment 1 or embodiment 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.

[0122] FIG. 17 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. 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 FIG. 2 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.

[0123] 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.

[0124] The control unit 6 generates switching signals to drive the two switching elements 220a and 220b using the control method described in embodiment 1 or embodiment 2. As a result, the AC-DC converter 2 shown in Fig. 17 can also achieve the same effects as those of embodiment 1 or embodiment 2.

[0125] 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.

[0126] Embodiment 9 In embodiment 9, a different example of the AC-DC converter 2 including the control unit 6 described in embodiment 1 or embodiment 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.

[0127] Fig. 18 is a diagram showing a configuration example of an AC-DC converter 2 according to a ninth embodiment. While the AC-DC converter 2 in Fig. 12 shows a single-phase AC power supply 1, Fig. 18 shows this changed to a three-phase AC power supply 5. As a result, in the AC-DC converter 2 in Fig. 18, the rectifier circuit 20 is configured with a three-phase full-bridge cell 226 including six switching elements 220a, 220b, 220c, 220d, 220e, and 220f. Reactors 212a, 212b, and 212c are inserted in each phase between the three-phase AC power supply 5 and the rectifier circuit 20, and current detectors 211a and 211b are arranged in any two of the three phases.

[0128] The voltage detection unit 227 detects the voltage of each phase of the three-phase AC power supply 5 and outputs the detected value to the control unit 6. The current detection units 211a and 211b detect the currents flowing in any two of the three phases and output the detected values ​​to the control unit 6. The current in the remaining phase can be determined by calculation within the control unit 6, taking advantage of the fact that the currents in the phases are three-phase balanced.

[0129] The control unit 6 generates switching signals for controlling the switching elements 220a, 220b, 220c, 220d, 220e, and 220f based on the detection values ​​of the voltage detection units 227 and 217b and the current detection units 211a and 211b. Note that the configuration and operation of the rectifier circuit 20 shown in Fig. 18 are publicly known, and further description thereof will be omitted here.

[0130] The control unit 6 generates switching signals to drive the six switching elements 220a, 220b, 220c, 220d, 220e, and 220f using the control method described in embodiment 1 or embodiment 2. As a result, the AC-DC converter 2 shown in FIG. 18 can also achieve the same effects as those of embodiment 1 or embodiment 2.

[0131] Although the switching elements 220a, 220b, 220c, 220d, 220e, and 220f are shown as IGBTs in FIG. 18 , any elements capable of switching operation may be used. 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 227 and 217b and the current detectors 211a and 211b do not need to be used. Furthermore, the control according to the ninth embodiment may be performed on an αβ coordinate system or a three-phase coordinate system.

[0132] Embodiment 10 In embodiment 10, a different example of the AC / DC converter 2 including the control unit 6 described in embodiment 1 or embodiment 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, 2, and 9 will be denoted by the same reference numerals, and overlapping descriptions will be omitted.

[0133] FIG. 19 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. 19, the rectifier circuit 20 includes a three-phase diode bridge cell 228 and a three-phase simplified PAM cell 229. The three-phase diode bridge cell 228 includes six diodes connected in a full bridge configuration. The three-phase simplified PAM cell 229 includes single-phase diode bridge cells 213a, 213b, and 213c, and switching elements 215a, 215b, and 215c connected in parallel to the single-phase diode bridge cells 213a, 213b, and 213c, respectively. The single-phase diode bridge cells 213a, 213b, and 213c are connected between the three-phase lines and the reactors 212a, 212b, and 212c and the three-phase diode bridge cell 228. The three-phase simple PAM cell 229 also includes a capacitor 216d, one end of which is connected to the single-phase diode bridge cells 213a, 213b, and 213c, and the other end of which is connected to the DC bus 9b. The capacitor 216d may be provided outside the three-phase simple PAM cell 229.

[0134] The control unit 6 generates switching signals for controlling the switching elements 215a, 215b, and 215c based on the detection values ​​of the voltage detection units 227 and 217b and the current detection units 211a and 211b. Note that the configuration and operation of the rectifier circuit 20 shown in Fig. 19 are publicly known, and further description thereof will be omitted here.

[0135] The control unit 6 generates switching signals to drive the three switching elements 215a, 215b, and 215c using the control method described in embodiment 1 or embodiment 2. As a result, the AC-DC converter 2 shown in Fig. 19 can also achieve the same effects as those of embodiment 1 or embodiment 2.

[0136] Although the switching elements 215a, 215b, and 215c are shown as IGBTs in FIG. 19 , any elements capable of switching operation may be used. Although the AC-DC converter 2 shown in FIG. 19 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 227 and 217b and the current detectors 211a and 211b do not need to be used. Furthermore, the control according to the tenth embodiment may be performed on an αβ coordinate system or a three-phase coordinate system.

[0137] Embodiment 11 In embodiment 11, a different example of the AC-DC converter 2 including the control unit 6 described in embodiment 1 or embodiment 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, 2, 9, and 10 will be denoted by the same reference numerals, and overlapping descriptions will be omitted.

[0138] Fig. 20 is a diagram showing a configuration example of an AC-DC converter 2 according to embodiment 11. In the AC-DC converter 2 of Fig. 20, the capacitor 216d is removed from the configuration of the AC-DC converter 2 of Fig. 19. Other configurations are the same as or equivalent to those of Fig. 19.

[0139] The control unit 6 generates switching signals for controlling the switching elements 215a, 215b, and 215c based on the detection values ​​of the voltage detection units 227 and 217b and the current detection units 211a and 211b. Note that the configuration and operation of the rectifier circuit 20 shown in Fig. 20 are publicly known, and further description thereof will be omitted here.

[0140] The control unit 6 generates switching signals to drive the three switching elements 215a, 215b, and 215c using the control method described in embodiment 1 or embodiment 2. As a result, the AC-DC converter 2 shown in Fig. 20 can also achieve the same effects as those of embodiment 1 or embodiment 2.

[0141] Although the switching elements 215a, 215b, and 215c are shown as IGBTs in FIG. 20 , any elements capable of switching operation may be used. Although the AC-DC converter 2 shown in FIG. 20 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 227 and 217b and the current detectors 211a and 211b do not need to be used. Furthermore, the control according to the eleventh embodiment may be performed on an αβ coordinate system or a three-phase coordinate system.

[0142] Embodiment 12 In embodiment 12, a different example of the AC-DC converter 2 including the control unit 6 described in embodiment 1 or embodiment 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, 2, and 9 will be denoted by the same reference numerals, and overlapping descriptions will be omitted.

[0143] Fig. 21 is a diagram showing a configuration example of an AC-DC converter 2 according to embodiment 12. In the AC-DC converter 2 shown in Fig. 21, the rectifier circuit 20 has a configuration called a full PAM circuit. The rectifier circuit 20 includes a three-phase diode bridge cell 228, a switching element 215, and a diode 218.

[0144] The control unit 6 generates a switching signal for controlling the switching element 215 based on the detection values ​​of the voltage detection units 227, 217b and the current detection unit 211. The configuration and operation of the rectifier circuit 20 shown in Fig. 21 are publicly known, and further description thereof will be omitted here.

[0145] The control unit 6 generates a switching signal for driving the switching element 215 using the control method described in the first or second embodiment. As a result, the AC-DC converter 2 shown in Fig. 21 can also achieve the same effects as those of the first or second embodiment.

[0146] Although the switching element 215 is shown as an IGBT in FIG. 21 , any element capable of switching operation may be used. Furthermore, although the AC-DC converter 2 shown in FIG. 21 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 227 and 217 b and the current detector 211 do not need to be used. Furthermore, the control according to the twelfth embodiment may be performed on an αβ coordinate system or a three-phase coordinate system.

[0147] Embodiment 13 In embodiment 13, a different example of the AC / DC converter 2 including the control unit 6 described in embodiment 1 or embodiment 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, 2, 9, and 12 will be denoted by the same reference numerals, and overlapping descriptions will be omitted.

[0148] Fig. 22 is a diagram showing a configuration example of an AC-DC converter 2 according to embodiment 13. In the AC-DC converter 2 of Fig. 22, the reactors 212a, 212b, and 212c that were arranged between the three-phase AC power supply 5 and the three-phase diode bridge cell 228 in the configuration of the AC-DC converter 2 of Fig. 21 are replaced with a reactor 212. In Fig. 22, the reactor 212 is arranged between the three-phase diode bridge cell 228 and the diode 218. The rest is the same as or equivalent to Fig. 21.

[0149] The control unit 6 generates a switching signal for controlling the switching element 215 based on the detection values ​​of the voltage detection units 227, 217b and the current detection unit 211. The configuration and operation of the rectifier circuit 20 shown in Fig. 22 are well known, and further description thereof will be omitted here.

[0150] The control unit 6 generates a switching signal for driving the switching element 215 using the control method described in the first or second embodiment. As a result, the AC-DC converter 2 shown in Fig. 22 can also achieve the same effects as those of the first or second embodiment.

[0151] Although the switching element 215 is shown as an IGBT in FIG. 22 , any element capable of switching operation may be used. Furthermore, although the AC-DC converter 2 shown in FIG. 22 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 227 and 217 b and the current detector 211 do not need to be used. Furthermore, the control according to the thirteenth embodiment may be performed on an αβ coordinate system or a three-phase coordinate system.

[0152] Embodiment 14 In embodiment 14, a different example of the AC-DC converter 2 including the control unit 6 described in embodiment 1 or embodiment 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, 2, and 9 will be denoted by the same reference numerals, and overlapping descriptions will be omitted.

[0153] FIG. 23 is a diagram illustrating a configuration example of an AC-DC converter 2 according to a fourteenth embodiment. In the AC-DC converter 2 of FIG. 23 , the rectifier circuit 20 is configured with a three-phase diode bridge cell 228 and a three-phase bidirectional switching cell 231. The three-phase bidirectional switching cell 231 includes six switching elements 231a, 231b, 231c, 231d, 231e, and 231f. Also, in FIG. 23 , the capacitor 216 of FIG. 18 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. In the three-phase bidirectional switching cell 231, the switching elements 231a and 231b, the switching elements 231c and 231d, and the switching elements 231e and 231f are connected in series in pairs. Each series-connected pair is arranged for each phase between the three-phase diode bridge cell 228 and the connection point of the capacitors 216 a, 216 b. Note that the configuration and operation of the rectifier circuit 20 shown in FIG. 23 are well known, and further description thereof will be omitted here.

[0154] The control unit 6 generates switching signals to drive the six switching elements 231a, 231b, 231c, 231d, 231e, and 231f using the control method described in embodiment 1 or embodiment 2. As a result, the AC-DC converter 2 shown in Fig. 23 can also achieve the same effects as those of embodiment 1 or embodiment 2.

[0155] Although the switching elements 231a, 231b, 231c, 231d, 231e, and 231f are shown as IGBTs in FIG. 23 , any elements capable of switching may be used. Although the AC-DC converter 2 shown in FIG. 23 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 227 and 217b and the current detectors 211a and 211b do not need to be used. Furthermore, the control according to the fourteenth embodiment may be performed on an αβ coordinate system or a three-phase coordinate system.

[0156] Embodiment 15 In embodiment 15, a different example of the AC-DC converter 2 including the control unit 6 described in embodiment 1 or embodiment 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.

[0157] FIG. 24 is a diagram illustrating a configuration example of an AC-DC converter 2 according to a fifteenth embodiment. In the AC-DC converter 2 of FIG. 24, a rectifier circuit 20 is configured with a single-phase diode bridge cell 213a and an interleaved cell 219. The interleaved cell 219 is configured by combining two sets of a reactor 212, a switching element 215, and a diode 218 in the full-PAM circuit configuration described in FIG. 12. 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. 24 are publicly known, and further description thereof will be omitted here.

[0158] The control unit 6 generates switching signals to drive the two switching elements 2193a and 2193b using the control method described in embodiment 1 or embodiment 2. As a result, the AC-DC converter 2 shown in Fig. 24 can also achieve the same effects as those of embodiment 1 or embodiment 2.

[0159] Although the switching elements 2193a and 2193b are shown as IGBTs in FIG. 24 , any elements capable of switching operation may be used. Furthermore, although the AC-DC converter 2 shown in FIG. 24 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. 24 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 fourteenth embodiments may also be configured in an interleaved configuration.

[0160] Sixteenth Embodiment Fig. 25 is a diagram showing a configuration example of a refrigeration cycle-applied device 900 according to a sixteenth embodiment. The refrigeration cycle-applied device 900 according to the sixteenth embodiment includes the rotating machine drive device 8 described in the first embodiment. The refrigeration cycle-applied device 900 according to the sixteenth embodiment can be applied to products equipped with a refrigeration cycle, such as air conditioners, refrigerators, freezers, and heat pump water heaters.

[0161] 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.

[0162] 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.

[0163] The refrigeration cycle applied device 900 according to the sixteenth 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 fifteenth 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 fifteenth embodiments, as long as the control method of the first or second embodiment can be applied.

[0164] 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.

[0165] 1 AC power supply, 2 AC / DC converter, 3 DC / AC converter, 4 Load, 5 Three-phase AC power supply, 6 Control unit, 8 Rotating machine drive device, 9a, 9b DC bus, 20 Rectifier circuit, 41 Motor, 42 Compressor, 211, 211a, 211b Current detection unit, 212, 212a, 212b, 212c, 2191a, 2191b Reactor, 213a, 213b, 213c Single-phase diode bridge cell, 215, 215a, 215b, 215c, 220a, 220b, 220c, 220d, 220e, 220f, 220g, 220h, 231a, 231b, 231c, 231d, 231e, 231f, 2193a, 2193b Switching elements, 216, 216a, 216b, 216c, 216d Capacitors, 217a, 217b, 217c, 227 Voltage detection unit, 218, 218a, 218b, 218c, 2192a, 2192b Diode, 219 Interleaved cell, 221 Single-phase H-bridge cell, 222, 225 Switching cell, 226 Three-phase full-bridge cell, 228 Three-phase diode bridge cell, 229 Three-phase simple PAM cell, 231 Three-phase bidirectional switching cell, 611, 614, 6172 Subtractor, 612 Voltage controller, 613 Multiplier, 615 Current controller, 616 Switching signal generator, 617 Sine wave signal generator, 900 Refrigeration cycle applied equipment, 902 Four-way valve, 904 Compression mechanism, 906 Indoor heat exchanger, 908 expansion valve, 910 outdoor heat exchanger, 912 refrigerant piping, 6171 PLL calculator, 6173 sine wave calculator, 6174 phase shift amount calculator.

Claims

1. An AC-DC conversion device comprising: a rectifier circuit having at least one switching element for rectifying a power supply voltage applied from an AC power supply; a capacitor connected to a DC bus for smoothing the output voltage of the rectifier circuit; a reactor disposed on the AC power supply side of the capacitor; a current detection unit for detecting a power supply current flowing between the AC power supply and the rectifier circuit; and a control unit for generating a switching signal for controlling the switching element, wherein the switching element is disposed on the AC power supply side of the capacitor, and the control unit generates the switching signal so as to change the phase of the power supply current.

2. The AC-DC conversion device according to claim 1, wherein the control unit generates the switching signal so as to change the phase of the power supply current based on a fundamental wave of the power supply current detected when the switching element is turned off and the rectifier circuit is operated passively.

3. The AC-DC conversion device according to claim 2, further comprising: a first voltage detection unit for detecting a bus voltage which is the voltage of the DC bus; and a second voltage detection unit for detecting the power supply voltage, wherein the control unit generates the switching signal so as to change the phase of the power supply current according to a magnitude relationship between a detected value of the bus voltage and a detected value of the power supply voltage.

4. The AC-DC conversion device according to claim 3, wherein the control unit calculates a phase shift amount based on a first phase at which the power supply current starts to flow when the rectifier circuit is operated passively and a second phase at which the flow of the power supply current ends after the power supply current flows, and changes the phase of the power supply current using the calculated phase shift amount.

5. The AC-DC conversion device according to claim 3, wherein the control unit calculates a phase shift amount using an optimization method and changes the phase of the power supply current using the calculated phase shift amount.

6. The AC-DC conversion device according to claim 5, wherein an evaluation function of the optimization method is associated with a harmonic component included in the power supply voltage or the power supply current.

7. The phase at which the power supply current becomes zero does not depend on the frequency of the power supply voltage and the inductance of the reactor, but has a property of changing according to a voltage ratio which is a ratio between the bus voltage which is the voltage of the DC bus and the effective value of the power supply voltage. The AC-DC conversion device according to any one of claims 1 to 6.

8. A rotary machine drive device comprising the AC-DC conversion device according to any one of claims 1 to 7.

9. A refrigeration cycle application device comprising the AC-DC conversion device according to any one of claims 1 to 7.

Images