JP2014007840A - Ac-dc conversion device and air conditioner having the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an AC-DC conversion device and an air conditioner therewith which reduce common mode noise further while suppressing an increase in loss.SOLUTION: The AC-DC conversion device includes: a first rectifier 2 for rectifying a voltage of an AC power supply 1; smoothing means 7 for smoothing an output voltage from the first rectifier 2; switch means 10a, 10b arranged nearer to the AC power supply 1 than the smoothing means 7; a first reactor 5 arranged nearer to the AC power supply 1 than the first rectifier 2; control means 20 for turning on/off the switch means 10a, 10b; and a second reactor 11 for suppressing a reverse current flowing from the smoothing means 7 to the AC power supply 1 via the first rectifier 2 when the switch means 10a, 10b is turned off.

Description

  The present invention relates to an AC / DC converter and an air conditioner including the same.

  As a conventional AC / DC converter, for example, two switching elements are provided, the two switching elements are PWM operated at a low frequency of 5 kHz or less, the output DC voltage is controlled to an arbitrary value, and the reference voltage is detected. DC voltage control is performed with a control value from the voltage, a converter voltage command with a sine wave waveform is generated based on this control, and the DC voltage output by the voltage difference from the power supply voltage is controlled to an arbitrary value. There is one that controls the input current in a substantially sinusoidal shape to suppress the harmonic current and feedback-controls the DC voltage to improve the power factor (for example, Patent Document 1).

  On the other hand, due to the switching operation of the switching element, a leakage current having a switching frequency flows in the input current and is conducted as common mode noise. For this reason, for example, a technique for reducing common mode noise by inserting a reactor provided on the AC side into both the R phase and the S phase is disclosed (for example, Patent Document 2).

  In addition, for example, by adding a leakage current compensation circuit, a zero-phase current is detected by a zero-phase current detection unit arranged on the DC side or the AC side, and a current is supplied so as to cancel the leakage current. Has been disclosed (for example, Patent Document 3).

International Publication No. 2009/028053 JP 2009-247121 A JP 2000-152692 A

  In recent years, conduction noise that has leaked into the electric power system may cause malfunction of peripheral devices through the electric power system. In particular, in Japan, it has come to be unified with overseas regulations that have been operated with strict regulatory values, and it is necessary to meet further noise reduction requirements. It has become a challenge.

  The present invention has been made in view of the above, and provides an AC / DC converter capable of further reducing common mode noise while suppressing an increase in loss, and an air conditioner including the same. Objective.

  In order to solve the above-described problems and achieve the object, an AC / DC converter according to the present invention includes a first rectifier that rectifies the voltage of an AC power supply, and a smoothing means that smoothes an output voltage from the first rectifier. Switching means arranged on the AC power supply side from the smoothing means, a first reactor arranged on the AC power supply side from the first rectifier, control means for opening and closing the switch means, And a second reactor that suppresses a backflow current that flows from the smoothing means to the AC power supply via the first rectifier when the switch means is closed.

  According to the present invention, it is possible to further reduce common mode noise while suppressing an increase in loss.

FIG. 1 is a diagram of a configuration example of the AC / DC converter according to the first embodiment. FIG. 2 is a diagram illustrating an equivalent circuit in an ideal state for explaining the operation principle of the AC / DC converter according to the first embodiment. FIG. 3 is a diagram illustrating an example of a control block in the control unit of the AC / DC converter according to the first embodiment. FIG. 4 is a diagram illustrating another example of the control block in the control unit of the AC / DC converter according to the first embodiment. FIG. 5 is a diagram for explaining an example of a current path in the configuration of a conventional AC / DC converter without a second reactor. FIG. 6 is a diagram for explaining an example of a current path in the AC / DC converter according to the first embodiment shown in FIG. 1. FIG. 7 is a diagram illustrating another configuration example of the AC / DC converter according to the first embodiment. FIG. 8 is a diagram illustrating another configuration example of the AC / DC converter according to the first embodiment. FIG. 9 is a diagram illustrating another configuration example of the AC / DC converter according to the first embodiment. FIG. 10 is a diagram of a configuration example of the AC / DC converter according to the second embodiment. FIG. 11 is a diagram illustrating an example of a control block in the control unit of the AC / DC converter according to the second embodiment. FIG. 12 is a diagram illustrating another configuration example of the AC / DC converter according to the second embodiment. FIG. 13 is a diagram illustrating a configuration example of an air conditioner according to the third embodiment.

  Hereinafter, an AC / DC converter according to an embodiment of the present invention and an air conditioner including the same will be described with reference to the accompanying drawings. In addition, this invention is not limited by embodiment shown below.

Embodiment 1 FIG.
FIG. 1 is a diagram of a configuration example of the AC / DC converter according to the first embodiment. As shown in FIG. 1, the AC / DC converter according to the first embodiment is configured to convert AC power supplied from an AC power source 1 into DC power and supply it to a DC load 8. A rectifier (first rectifier) 2 that rectifies the voltage of 1 and two smoothing capacitors 6a and 6b connected in series, a smoothing means 7 that smoothes the output voltage from the rectifier 2, and a first rectifier 2, a first bidirectional switch (switching means) 10a inserted between one input terminal of the two and the connection point of the smoothing capacitors 6a, 6b, the other input terminal of the first rectifier 2, and the smoothing capacitors 6a, A second bidirectional switch (switch means) 10b inserted between the connection point 6b, a first reactor 5 inserted between the AC power supply 1 and one input terminal of the rectifier 2, and a rectifier One output of 2 A second reactor 11a, 11b having a microreactance value inserted between both the child and one end of the smoothing means 7 and between the other output terminal of the rectifier 2 and the other end of the smoothing means 7, Based on the detected values detected by the DC voltage detector 21, the input current detector 22, and the power supply voltage detector 23, the first bidirectional switch 10a and the second bidirectional switch 10b are operated to generate a DC load. And a control means 20 for controlling the output voltage value applied to 8. The rectifier 2 is configured by bridge-connecting four rectifier diodes 2a to 2d.

  The first bidirectional switch 10a is composed of a switching element 3a and a diode rectifier 4a, and the second bidirectional switch 10b is similarly composed of a switching element 3b and a diode rectifier 4b. In the example illustrated in FIG. 1, an example in which IGBTs are provided as the switching elements 3 a and 3 b is illustrated. Further, in the example shown in FIG. 1, the voltage across the AC power supply 1 is Vs, the voltage between a and b in FIG. 1 is Vc *, and the current flowing through the first reactor 5 is I.

  Next, the operation principle of the AC / DC converter according to the first embodiment will be described with reference to FIG. FIG. 2 is a diagram illustrating an equivalent circuit in an ideal state for explaining the operation principle of the AC / DC converter according to the first embodiment. The AC power supply 1 and the first reactor 5 are the same as those shown in FIG. 1, and the configuration when the DC load 8 side is viewed from ab in FIG. Also, the voltage across the AC power supply 1 is Vs, the voltage across the virtual AC power supply 9 (that is, the voltage between a and b in FIG. 1) is Vc *, and the current flowing through the first reactor 5 is I. The same as FIG. The AC / DC converter according to the first embodiment is realized by operating two bidirectional switches 10a and 10b mutually as represented by a virtual AC power supply 9 as shown in FIG.

  The difference voltage between the AC power supply 1 and the virtual AC power supply 9 determines the current I flowing through the first reactor 5. If the voltage Vc * output from the virtual AC power supply 9 is sinusoidal, the current I flowing through the first reactor 5, that is, the input current of the virtual AC power supply 9, is a sinusoidal current, and the harmonic current is It is suppressed. When the phase difference between the current I and the AC power source 1 becomes zero, the power factor becomes 100%. Therefore, the amplitude | Vc * | in the virtual AC power source 9 and the phase difference φ between the AC power source 1 are appropriately set. If controlled to output a sine wave voltage, the harmonics of the input current can be suppressed and the power source power factor can be improved.

  Next, control means of the AC / DC converter according to the first embodiment will be described with reference to FIG. FIG. 3 is a diagram illustrating an example of a control block in the control unit of the AC / DC converter according to the first embodiment.

  A difference between the DC voltage command value Vdc * and the DC voltage detection value Vdc detected by the DC voltage detector 21 is input to the PI controller 30. The PI controller 30 outputs a current command value Ip * such that the difference between the input DC voltage command value Vdc * and a preset DC voltage detection value Vdc is zero.

  On the other hand, the instantaneous value Is of the input current detected by the input current detector 22 and the phase angle θ of the power supply voltage detected by the power supply voltage detector 23 are input to the PQ converter 31. The PQ converter 31 separates the active power component (P-axis component) of the input current into the reactive power component (Q-axis component) of the input current.

  A difference between the current command value Ip * and the active power component Ip of the input current filtered by the LPF 32a is input to the PI controller 33. The PI controller 33 calculates the active power component Vp * of the voltage command value at both ends so that the difference between the current command value Ip * and the active power component Ip of the input current becomes zero.

  The PI controller 34 receives the difference between zero and the reactive power component Iq of the input current filtered by the LPF 32b. The PI controller 34 calculates the reactive power component Vq * of the voltage command value at both ends so that the difference between zero and the reactive power component Iq of the input current is zero, that is, the reactive power component Iq of the input current is zero.

  The inverse PQ converter 35 receives the active power component Vp * of the both-end voltage command value, the reactive power component Vq * of the both-end voltage command value, and the phase angle θ of the power supply voltage. The inverse PQ converter 35 inversely converts the active power component Vp * of the both-end voltage command value and the reactive power component Vq * of the both-end voltage command value, and outputs the both-end voltage command value Vc * of the virtual AC power supply 9.

  By controlling in this way, the power source power factor is 100%, that is, the reactive power component of the current becomes zero, and the output DC voltage supplied to the DC load 8 can be controlled to become the DC voltage command value Vdc *. It becomes possible.

  FIG. 4 is a diagram illustrating another example of the control block in the control unit of the AC / DC converter according to the first embodiment. Instead of the control block example shown in FIG. 3, as shown in FIG. 4, it is possible to adopt a configuration using the property that the vector relation of the voltage / current is orthogonal when the power factor = 100%. Since the configuration of the control block shown in FIG. 4 is known (for example, Patent Document 1), detailed description thereof is omitted here.

  With the control block configuration as shown in FIG. 3 and FIG. 4 described above, the PWM switching operation is performed at a low frequency of 5 kHz or less by combining the ON / OFF operation of the first bidirectional switch 10a and the second bidirectional switch 10b. Thus, the power source power factor can be improved while suppressing the harmonic current.

  On the other hand, although the frequency is low, noise is generated when the first bidirectional switch 10a and the second bidirectional switch 10b are PWM-switched, and a leakage current having a switching frequency flows in the input current.

  Here, there are two types of noise, common mode and normal mode. The common mode is generally generated by a potential difference from the ground (ground), and the normal mode is generally generated by a potential difference between terminals of the apparatus. For example, it is possible to insert a reactor provided on the AC side (corresponding to the first reactor 5 here) into both the R phase and the S phase, or to use the common mode choke coil as a common mode. There are known techniques that make it possible to suppress mode noise.

  In addition, a leakage current compensation circuit that compensates for the leakage current that flows due to the zero-phase current that is the source of common mode noise is added, and the zero-phase current is detected by the zero-phase current detector located on the DC or AC side. Although there is a known technology that makes it possible to suppress common mode noise by flowing current so as to cancel current leaking to the housing, it can be canceled depending on the accuracy and detection delay of zero-phase current detection. However, there is a possibility that the leakage current is increased by compensating in the reverse direction.

  In recent years, conduction noise that has leaked into the electric power system may cause malfunction of peripheral devices through the electric power system. In particular, the domestic regulation value has been unified with the overseas regulation value that has been operated with strict regulation values from the past, and it is necessary to meet further noise reduction requirements. Reduction is an issue.

  In the first embodiment, as shown in FIG. 1, between one output terminal of the rectifier 2 and one end of the smoothing means 7, and between the other output terminal of the rectifier 2 and the other end of the smoothing means 7. As a configuration in which the second reactors 11a and 11b having minute reactance values are inserted between the two, the common mode noise can be further reduced. Hereinafter, the reduction of the common mode noise by the second reactors 11a and 11b in the AC / DC converter according to the first embodiment will be described with reference to FIG. 1, FIG. 5, and FIG. FIG. 5 is a diagram for explaining an example of a current path in the configuration of a conventional AC / DC converter without a second reactor. FIG. 6 is a diagram for explaining an example of a current path in the AC / DC converter according to the first embodiment shown in FIG. 1. In the following description, it is assumed that the AC power source 1 is a positive electrode when the potential a shown in FIGS. 5 and 6 is higher than the potential b.

  The AC / DC converter shown in FIGS. 1, 5 and 6 operates by turning on / off the first bidirectional switch 10a and the second bidirectional switch 10b. In the conventional configuration example shown in FIG. 5, when the first bidirectional switch 10a and the second bidirectional switch 10b are turned on / off, the recovery characteristics of the rectifier diodes 2a, 2b, 2c, and 2d of the rectifier 2 are obtained. Current flows due to the recovery characteristics, and the current flowing due to this recovery characteristic leaks to the power system, generating common mode noise.

  In the conventional configuration example shown in FIG. 5, when the AC power supply 1 is a positive electrode and the first bidirectional switch 10 a and the second bidirectional switch 10 b are both off, the current path of the input current is A path (path indicated by a broken line in FIG. 5A) flows in the order of AC power supply 1 -first reactor 5 -rectifier diode 2 a -smoothing capacitor 6 a -smoothing capacitor 6 b -diode 2 b. Here, let this current path be path 1.

  When the first bidirectional switch 10a is turned on from the state of the path 1, the current path of the input current is: AC power source 1-first reactor 5-first bidirectional switch 10a-smoothing capacitor 6b-rectifier diode 2b. It changes to a route that flows in sequence (route indicated by a one-dot chain line in FIG. 5B). Here, let this current path be path 2.

  If each of the rectifier diodes 2a, 2b, 2c, and 2d constituting the rectifier 2 is an ideal diode, the transition from the path 1 to the path 2 described above is made. In general, the rectifier diode is changed from the forward bias to the reverse bias. When the transition is made, the reverse current can flow by the accumulated carriers. The time during which the reverse flow is possible is called a recovery time (reverse recovery time), and a recovery time from when the bidirectional switch 10a is turned on until the rectifier diode 2a actually prevents the reverse flow occurs. In other words, during the transition from the path 1 to the path 2, the short-circuit path of the smoothing capacitor 6a through which the current flows in the order of the smoothing capacitor 6a, the rectifier diode 2a, and the first bidirectional switch 10a (the path indicated by the solid line in FIG. 5C). ) Is generated, and an excessive current flows instantaneously.

  At this time, the reverse current generated by the recovery characteristic of the rectifier diode 2a, that is, the recovery current is superimposed on the current flowing from the AC power supply 1 at the point a of the input terminal of the rectifier 2. Since the potential at the point a of the rectifier 2 is different from the ground by the amount of the recovery current superimposed, common mode noise, which is noise of a potential difference with respect to the ground (earth) potential, is generated. That is, if there is no potential fluctuation due to the recovery current, in other words, if the potential balance with respect to the ground potential of the input terminal of the rectifier 2 is ensured, common mode noise associated with the ON operation of the first switch means does not occur. That is, in the conventional configuration shown in FIG. 5, the recovery current of each rectifier diode constituting the rectifier 2 is the main cause of common mode noise.

  Compared to the conventional configuration shown in FIG. 5, in the AC / DC converter according to the present embodiment, as shown in FIGS. 1 and 6, between one output terminal of the rectifier 2 and one end of the smoothing means 7, In addition, second reactors 11 a and 11 b having minute reactance values are inserted between the other output terminal of the rectifier 2 and the other end of the smoothing means 7. By adopting such a configuration, the above-described path 1 includes: AC power source 1 −first reactor 5 −rectifier diode 2a−second reactor 11a−smoothing capacitor 6a−smoothing capacitor 6b−second reactor 11b−diode. 2b flows in the order of 2b (path indicated by a broken line in FIG. 6A), and the path 2 is AC power source 1-first reactor 5-first bidirectional switch 10a-smoothing capacitor 6b-second reactor 11b. A path that flows in the order of the rectifier diode 2b (path indicated by a one-dot chain line in FIG. 6B), and the short-circuit path of the smoothing capacitor 6a generated by the recovery characteristic of the rectifier diode 2a during the transition from the path 1 to the path 2 is Smoothing capacitor 6a-first reactor 11a-rectifier diode 2a-first bidirectional switch 10a (Path indicated by the solid line in Figure 6 (c)).

  Here, when a current is flowing, the reactor has a property of suppressing the current to flow continuously, and conversely, at the moment when the current flowing direction is reversed. In order to suppress the reverse current, no current flows instantaneously.

  Therefore, from the state of the path 1 in which both the first bidirectional switch 10a and the second bidirectional switch 10b are off (the state shown in FIG. 6A), the moment when the first bidirectional switch 10a is turned on, Even if the reverse current of the rectifier diode 2a, that is, the reverse current of the smoothing capacitor 6a is about to flow through the short-circuit path of the smoothing capacitor 6a shown in FIG. 6C due to the recovery characteristics of the rectifying diode 2a, the second reactor 11a The backflow current is suppressed. That is, the occurrence of the short circuit path of the first capacitor 6a shown in FIG. 6C is suppressed, and the state transits to the path 2 shown in FIG. 6B.

  Further, from the state transition described above, that is, the state where both the first bidirectional switch 10a and the second bidirectional switch 10b are off when the AC power supply 1 is positive (the state shown in FIG. 6A). Even in a state transition other than when the first bidirectional switch 10a is turned on, a short circuit path of each smoothing capacitor 6a, 6b is generated by the recovery characteristics of each rectifier diode 2a, 2b, 2c, 2d constituting the rectifier 2. For this reason, the second reactors 11 a and 11 b are provided between one output terminal of the rectifier 2 and one end of the smoothing means 7 and between the other output terminal of the rectifier 2 and the other end of the smoothing means 7. It is set as the structure which inserted.

  For example, when the AC power supply 1 is positive, the first bidirectional switch 10a and the second bidirectional switch 10b are both turned off (the state shown in FIG. 6A) to the second bidirectional switch 10b. In the state transition when ON is turned on, the reverse current of the rectifier diode 2d, that is, the reverse current of the smoothing capacitor 6b flows through the short-circuit path of the smoothing capacitor 6b generated by the recovery characteristic of the rectifier diode 2d. The backflow current is suppressed by the reactor 11b.

  The reactance values of the second reactors 11a and 11b are smaller than the reactance values of the first reactor 5, and the second reactors 11a and 11b do not act to improve the power source power factor or reduce the harmonic current. What is necessary is just to make it the same microreactance value of the grade which does not affect the loss by the voltage drop in reactor 11a, 11b, or DC voltage fall.

  By adopting such a configuration, it is possible to suppress the increase in loss due to the insertion of the second reactors 11a and 11b and improve the power source power factor, and the rectifier diodes 2a, 2b, 2c, Common mode noise generated by the 2d recovery characteristic can be reduced.

  Furthermore, the second reactors 11a and 11b may be configured to use a saturable reactor that has a high impedance when not saturated and a low impedance when saturated, and is designed to be saturated at the rated current. Moreover, you may comprise the saturable reactor which controls the operation coil side so that an impedance may change. If it does in this way, since it will become a low impedance because the 2nd reactor 11a, 11b will be in the state which became saturated in the rated current, generation | occurrence | production of the loss in 2nd reactor 11a, 11b can be suppressed. On the other hand, when the reverse current of the smoothing capacitors 6a and 6b starts to flow due to the recovery characteristics of the rectifier diodes 2a, 2b, 2c and 2d constituting the rectifier 2, the second reactors 11a and 11b are not saturated. Due to the state, the impedance becomes high, and the generation of the backflow current is suppressed by the above-described properties as a reactor. By comprising in this way, it becomes possible to reduce common mode noise, suppressing generation | occurrence | production of the loss by inserting 2nd reactor 11a, 11b.

  7, 8, and 9 are diagrams illustrating another configuration example of the AC / DC converter according to the first embodiment. In the configuration example shown in FIG. 1, the example in which the first reactor 5 is inserted into one path between the AC power source 1 and the rectifier 2 is shown. However, as shown in FIG. 7, the AC power source 1 and the rectifier 2 are inserted. The first reactors 5a and 5b can be inserted into both paths between the two. If comprised in this way, in addition to the reduction effect of the common mode noise by having comprised 2nd reactor 11a, 11b, the reduction effect of a common mode noise can be heightened further.

  Further, as shown in FIG. 8, instead of the first bidirectional switches 10a and 10b, a second rectifier 12 whose input terminal is connected in parallel with the input terminal of the rectifier (first rectifier) 2, The first switching element 3a inserted between one output terminal of the second rectifier 12 and the connection point of the smoothing capacitors 6a and 6b, and the other output terminal of the second rectifier 12 and the smoothing capacitors 6a and 6b. It is good also as a structure provided with the 2nd switching element 3b inserted between connection points.

  Further, in the configuration example shown in FIG. 1, the first bidirectional switch 10a is composed of a switching element 3a and a diode rectifier 4a, and the second bidirectional switch 10b is composed of a switching element 3b and a diode rectifier 4b. As shown in FIG. 9, the first switching element 3aa and the first diode 4aa connected in series, the second switching element 3ab and the second diode 4ab connected in series, Are connected in antiparallel to form a first bidirectional switch 10a, and similarly, a third switching element 3ba and a third diode 4ba connected in series, and a fourth switching element 3bb connected in series and The second bidirectional switch 10b may be configured by connecting the fourth diode 4bb in antiparallel.

  In the example shown in FIG. 9, the connection point between the first switching element 3aa and the first diode 4aa and the connection point between the second switching element 3ab and the second diode 4ab are not connected. These connection points may be connected, and similarly, the connection point between the third switching element 3ba and the third diode 4ba, and the fourth switching element 3bb and the fourth diode 4bb. Although the connection point is not connected, the structure which connected these connection points may be sufficient.

  Further, in the example shown in FIGS. 8 and 9, the first reactors 5a and 5b are respectively inserted into both paths between the AC power source 1 and the rectifier 2 as in the example shown in FIG. It goes without saying that the first reactor 5 may be inserted into one path between the AC power supply 1 and the rectifier 2 as in the example shown in FIG.

  As described above, according to the AC / DC converter of the first embodiment, the smoothing capacitor flowing in the short-circuit path of the smoothing capacitor generated by the recovery characteristics of the rectifier diodes constituting the rectifier when the switch unit is turned on. Since a reactor having a minute reactance value (second reactor) that suppresses the backflow current is inserted between the output terminal of the rectifier and the smoothing means, an increase in loss due to insertion of the reactor is suppressed, and a common mode is suppressed. Generation of a recovery current of each rectifier diode, which is a main cause of noise, can be suppressed, and common mode noise can be reduced.

  Further, it can be used in combination with other known techniques for suppressing common mode noise, and it is possible to further reduce common mode noise.

  Furthermore, it is configured to use a saturable reactor that is high impedance when not saturated and low impedance when saturated, and is designed to be saturated at the rated current, so that the reactor is saturated at the rated current. Since it becomes low impedance by this, the loss generation | occurrence | production in a reactor is suppressed. On the other hand, when the recovery current of each rectifier diode composing the rectifier starts to flow as the switch means is turned on, the reactor is not saturated, resulting in high impedance, and the generation of recovery current is suppressed. Is done. With this configuration, it is possible to reduce common mode noise while minimizing an increase in loss due to insertion of a reactor.

  Further, in each configuration described in the first embodiment described above, the power supply power factor can be improved while suppressing the harmonic current by causing the switch means to perform the PWM switching operation at a low frequency of, for example, 5 kHz or less, Furthermore, a highly efficient AC / DC converter with little switching loss can be obtained.

  In the first embodiment described above, the switching elements constituting the first bidirectional switch and the second bidirectional switch are IGBTs. However, for example, the switching element has a p layer deeper than a normal MOSFET. By using a MOSFET with a super-junction structure that has a high voltage resistance while having a low on-resistance because its p layer is in wide contact with the n layer, the switching loss of each switching element can be reduced and the loss can be further reduced. A highly efficient AC / DC converter that realizes the above can be obtained.

  Also, wide band gaps such as GaN (gallium nitride), SiC (silicon carbide), diamond, etc., which have better recovery characteristics and shorter recovery times than conventional semiconductor elements composed of Si (silicon) based semiconductors. By using a rectifier diode or rectifier (first rectifier) formed of a semiconductor (hereinafter referred to as “WBG”), the recovery current is relatively reduced by shortening the recovery time, thereby reducing common mode noise. The effect can be further enhanced.

  In addition, since the above-described WBG semiconductor element has characteristics that the switching speed is high and the switching loss is small, both the first bidirectional switch and the second switch are formed using the switching element formed of the WBG semiconductor. By configuring the direction switch, it is possible to further improve the efficiency of the AC / DC converter.

Embodiment 2. FIG.
FIG. 10 is a diagram of a configuration example of the AC / DC converter according to the second embodiment. In addition, the same code | symbol is attached | subjected to the component which is the same as that of Embodiment 1, or equivalent, and the detailed description is abbreviate | omitted. As shown in FIG. 10, the AC / DC converter according to the first embodiment includes a smoothing capacitor 14 that is a smoothing means that smoothes the output voltage from the rectifier 2, a first reactor 5, and a switching element (switching means) 13. And a chopper circuit 16 including a backflow prevention diode 15 and a second reactor 11 inserted between the chopper circuit 16 and the smoothing capacitor 14. In the example illustrated in FIG. 10, an example in which an IGBT is provided as the switching element 13 is illustrated.

  Next, control means of the AC / DC converter according to the second embodiment will be described with reference to FIG. FIG. 11 is a diagram illustrating an example of a control block in the control unit of the AC / DC converter according to the second embodiment.

  A difference between the DC voltage command value Vdc * and the DC voltage detection value Vdc detected by the DC voltage detector 21 is input to the PI controller 30. The PI controller 30 outputs a current peak command value Iss * such that the difference between the input DC voltage command value Vdc * and a preset DC voltage detection value Vdc is zero.

  The multiplier 36 receives the current peak command value Iss * and the instantaneous value Vs of the power supply voltage detected by the power supply voltage detector 23. The multiplier 36 multiplies the current peak command value Iss * and the AC voltage Vs to obtain the current command value Is *.

  A deviation between the current command value Is * and the input current Is detected by the input current detector 22 is input to the PI controller 37. The PI controller 37 calculates the duty command duty * of the switching element 13 such that the deviation between the current command value Is * and the input current Is becomes zero. In FIG. 10, the input current detector 22 is inserted between the AC power supply 1 and the rectifier 2, but the input current detector 22 may be inserted between the chopper circuit 16 and the rectifier 2, In this case, it goes without saying that the power supply voltage Vs input to the multiplier 36 in FIG. 11 can be realized with the same configuration as long as it is input as an absolute value.

  Next, reduction of common mode noise by the second reactor 11 in the AC / DC converter according to the second embodiment will be described with reference to FIG.

  In the configuration example shown in FIG. 10, when the second reactor 11 is not provided, the short-circuit path of the smoothing capacitor 14 is generated by the recovery characteristic of the backflow prevention diode 15 when the switching element 13 is turned on. The recovery current of the backflow prevention diode 15, that is, the backflow current of the smoothing capacitor 14 flows through the short-circuit path of the smoothing capacitor 14. That is, the recovery current of the backflow prevention diode 15 is a main cause of common mode noise.

  In the configuration example shown in FIG. 10, when the control block example shown in FIG. 11 is applied, the PWM switching operation is performed at a high frequency of 15 kHz or more, for example, unlike the configuration examples described in the above-described embodiment. Therefore, in the configuration without the second reactor 11, more common mode noise is generated than in the conventional configuration example shown in FIG. 5 described in the first embodiment.

  That is, since the frequency at which the switching element 13 is turned on is higher than in the first embodiment, the ratio of the total time of the recovery time per unit time is increased, and the backflow prevention diode 15 generated with the discharge of the smoothing capacitor 14. The rate of current change due to the recovery current increases. Therefore, more common mode noise is generated than in the conventional configuration example shown in FIG. 5 described in the first embodiment.

  Therefore, also in the present embodiment, as shown in FIG. 10, by inserting the reactor 11 having a minute reactance value between the chopper circuit 16 and the smoothing capacitor 14 as in the first embodiment, The rate of change in current due to 15 recovery currents is suppressed. Thereby, even in the configuration in which the PWM switching operation is performed at a high frequency described with reference to FIGS. 10 and 11, the occurrence of common mode noise can be suppressed.

  In addition, although the example shown in FIG. 10 has shown the example which inserted the 2nd reactor 11 between the backflow prevention diode 15 and the smoothing capacitor 14, the position which inserts the 2nd reactor 11 is not restricted to this. Needless to say, the second reactor 11 may be inserted between the switching element 13 and the backflow prevention diode 15 and may be anywhere on the same current path as the backflow prevention diode 15.

  Further, the reactance value of the second reactor 11 is smaller than the reactance value of the first reactor 5 as in the first embodiment, and does not affect the improvement of the power factor and the reduction of the harmonic current, or The microreactance value may be set so as not to affect the loss due to the voltage drop in the second reactor 11 or the DC voltage drop.

  Further, as in the first embodiment, the second reactor 11 may be a saturable reactor, and it goes without saying that the same effect as in the first embodiment can be obtained. Moreover, you may comprise the saturable reactor which controls the operation coil side so that an impedance may change.

  FIG. 12 is a diagram illustrating another configuration example of the AC / DC converter according to the second embodiment. In the configuration example shown in FIG. 10, an example in which one set of the chopper circuit 16 including the first reactor 5, the switching element (switch means) 13, and the backflow prevention diode 15 is provided is shown. A chopper circuit 16a comprising a first reactor 5a, a switching element (switch means) 13a, and a backflow prevention diode 15a, and a chopper circuit 16b comprising a first reactor 5b, a switching element (switch means) 13b, and a backflow prevention diode 15b. The second reactors 11a and 11b may be provided for each of the two sets of chopper circuits 16a and 16b. Furthermore, each of the choppers may be configured to include three or more sets of chopper circuits. The structure provided with the 2nd reactor for every circuit may be sufficient. Alternatively, the second reactor may not be provided for each of the plurality of chopper circuits, and one second reactor may be provided in the synthesis unit of the current flowing through each chopper circuit.

  As described above, the AC / DC converter according to Embodiment 2 includes one or more sets of chopper circuits including a first reactor, a switching element (switching means), and a backflow prevention diode, and performs PWM at high frequency. Even in the configuration in which the switching operation is performed, the second reactor having a minute reactance value that suppresses the backflow current of the smoothing capacitor that flows in the short-circuit path of the smoothing capacitor that is generated by the recovery characteristic of the backflow prevention diode when the switching element is turned on. Is inserted on the same current path as the backflow prevention diode, thereby suppressing the increase in loss due to the insertion of the reactor and suppressing the generation of recovery current of the backflow prevention diode, which is the main cause of common mode noise. And common mode noise can be reduced.

  In addition, since the recovery current of the backflow prevention diode is suppressed, the current flowing when the switching element is turned on can be reduced, so that the switching loss can be reduced. The reduction effect is greater.

  Further, similarly to the first embodiment, it can be used in combination with other known techniques for suppressing common mode noise, and further reduction of common mode noise is possible.

  Further, as in the first embodiment, the saturable reactor is configured so as to have a high impedance in a non-saturated state and a low impedance in a saturated state. Then, since the impedance becomes low when the reactor is saturated, the occurrence of loss in the reactor is suppressed. On the other hand, when the recovery current of the backflow prevention diode starts to flow along with the ON operation of the switching element, the reactor is not saturated and the impedance becomes high, and the generation of the recovery current is suppressed. By comprising in this way, it becomes possible to reduce common mode noise, suppressing generation | occurrence | production of the loss by inserting a reactor.

  In the first embodiment described above, an example in which the switching element is an IGBT has been shown. However, similarly to the first embodiment, by using a super junction structure MOSFET, the switching loss of the switching element can be reduced. This can improve the efficiency of the AC / DC converter.

  As in the first embodiment, the recovery time is shortened by using a rectifier diode or a rectifier (first rectifier) formed of a WBG semiconductor having excellent recovery characteristics and a short recovery time. As a result, the recovery current becomes relatively small, so that the common mode noise reduction effect can be further enhanced.

  Further, similarly to the first embodiment, by using a switching element formed of a WBG semiconductor having a high switching speed and a small switching loss, it is possible to further increase the efficiency of the AC / DC converter. it can.

Embodiment 3 FIG.
In the present embodiment, an air conditioner including the AC / DC converter described in Embodiment 1 and Embodiment 2 will be described.

  FIG. 13 is a diagram illustrating a configuration example of an air conditioner according to the third embodiment. As shown in FIG. 13, the air conditioner according to the third embodiment uses the AC / DC converter 40 described in the first and second embodiments and the DC power supplied from the AC / DC converter 40 as an AC. Inverter 41 for converting to electric power, electric motor 58 driven by AC power supplied from inverter 41, current detectors 42a and 42b for detecting the current flowing through electric motor 58, current detectors 42a and 42b, and a voltage detector 44, a drive control unit 43 that drives and controls the electric motor 58, a compressor 51 including the electric motor 58, a four-way valve 52, an outdoor heat exchanger 53, an expansion valve 54, and indoor heat. The exchanger 55 includes a refrigeration cycle attached via a refrigerant pipe 56.

  The compressor 51 includes a compression mechanism 57 that compresses the refrigerant and an electric motor 58 that operates the compressor. The refrigerant circulates from the compressor 51 between the outdoor heat exchanger 53 and the indoor heat exchanger 55. By doing so, a refrigeration cycle for performing cooling and heating, freezing and the like is configured.

  The AC / DC converter 40 described in the first embodiment and the second embodiment can reduce common mode noise while suppressing an increase in loss. For this reason, as shown in FIG. 13, by applying the AC / DC converter 40 with higher efficiency and higher common mode noise reduction effect to the air conditioner, the energy-saving performance of the air conditioner is not impaired. It becomes possible to increase the power voltage of the compressor motor by improving the power source power factor and increasing the DC voltage, and to reduce the loss by reducing the current.

  As described above, according to the air conditioner of the third embodiment, the AC / DC converter that further enhances the high efficiency and the reduction effect of the common mode noise described in the first and second embodiments. By applying it, it is possible to improve the power factor of the air conditioner, increase the voltage of the compressor motor by increasing the DC voltage, and reduce the loss by reducing the current without impairing the energy saving performance of the air conditioner.

  In the above-described embodiment, the AC power source is a single-phase AC power source and the rectifier (first rectifier) is a single-phase rectifier. However, the AC power source is a three-phase AC power source, and the rectifier (first Needless to say, the effects of the above-described embodiments can be obtained even if the rectifier 1 is a three-phase rectifier.

  In addition, the effect obtained by using a semiconductor element such as a switching element, a rectifier diode, or a backflow prevention diode constituted by the WBG semiconductor described in the above-described embodiment is not limited to the effect described in the above-described embodiment.

  For example, a semiconductor element made of a WBG semiconductor has high withstand voltage and high allowable current density, so that the semiconductor element can be downsized. By using these downsized semiconductor elements, these semiconductor elements can be used. The AC / DC converter incorporating the element can be miniaturized.

  In addition, since the semiconductor element composed of the WBG semiconductor has high heat resistance as described above, it is possible to reduce the size of the radiating fin of the radiating means, thereby further reducing the size of the AC / DC converter. Therefore, it is possible to reduce the size and cost of an air conditioner incorporating the AC / DC converter.

  Note that the configuration shown in the above embodiment is an example of the configuration of the present invention, and can be combined with another known technique, and a part thereof is omitted without departing from the gist of the present invention. Needless to say, it is possible to change the configuration.

1 AC power supply 2 Rectifier (first rectifier)
2a, 2b, 2c, 2d Rectifier diode 3a Switching element (first switching element)
3aa 1st switching element 3ab 2nd switching element 3b Switching element (2nd switching element)
3ba 3rd switching element 3bb 4th switching element 4a, 4b Diode rectifier 4aa 1st diode 4ab 2nd diode 4ba 3rd diode 4bb 4th diode 5, 5a, 5b 1st reactor 6a, 6b Smoothing Capacitor (smoothing means)
7 Smoothing means 8 DC load 10a First bidirectional switch (switch means)
10b Second bidirectional switch (switch means)
11, 11a, 11b Second reactor 12 Second rectifier 13, 13a, 13b Switching element (switch means)
14 Smoothing capacitor (smoothing means)
15, 15a, 15b Backflow prevention diode 16, 16a, 16b Chopper circuit 20 Control means 21 DC voltage detector 22 Input current detector 23 Power supply voltage detector 30 PI controller 31 PQ converter 32a, 32b LPF
33 PI Controller 34 PI Controller 35 Inverse PQ Converter 36 Multiplier 37 PI Controller 40 AC / DC Converter 41 Inverter 42a Current Detector 42b Current Detector 43 Drive Control Unit 44 Voltage Detector 51 Compressor 52 Four Way Valve 53 Outdoor heat exchanger 54 Expansion valve 55 Indoor heat exchanger 56 Refrigerant piping 57 Compression mechanism 58 Electric motor

Claims (15)

A first rectifier for rectifying the voltage of the AC power supply;
Smoothing means for smoothing the output voltage from the first rectifier;
Switch means disposed closer to the AC power supply than the smoothing means;
A first reactor disposed closer to the AC power supply than the first rectifier;
Control means for opening and closing the switch means;
A second reactor that suppresses a backflow current flowing from the smoothing means to the AC power source through the first rectifier during the closing operation of the switch means;
An AC / DC converter characterized by comprising: The smoothing means is composed of two smoothing capacitors connected in series,
The switch means includes a first bidirectional switch inserted between one input terminal of the first rectifier and a connection point of the smoothing capacitor, and the other input terminal of the first rectifier and the It is constituted by a second bidirectional switch inserted between the connection point of the smoothing capacitor,
The second reactor is between one output terminal of the first rectifier and one end of the smoothing means, and between the other output terminal of the first rectifier and the other end of the smoothing means. The AC / DC converter according to claim 1, wherein the AC / DC converter is inserted into both of the two.   The AC / DC converter according to claim 2, wherein each of the first bidirectional switch and the second bidirectional switch includes at least a diode rectifier and a switching element. The first bidirectional switch includes a first switching element connected in series and a second switching element connected in series with a first diode and a second diode connected in antiparallel,
The second bidirectional switch is configured by connecting a third switching element connected in series and a fourth switching element connected in series with a third diode, and a fourth diode connected in antiparallel. The AC / DC converter according to claim 2. A second rectifier having an input terminal connected in parallel with the input terminal of the first rectifier;
The smoothing means is composed of two smoothing capacitors connected in series,
The switch means includes a first switching element inserted between one output terminal of the second rectifier and a connection point of the smoothing capacitor, and the other output terminal of the second rectifier and the smoothing. A second switching element inserted between the connection point of the capacitor and
The second reactor is between one output terminal of the first rectifier and one end of the smoothing means, and between the other output terminal of the first rectifier and the other end of the smoothing means. The AC / DC converter according to claim 1, wherein the AC / DC converter is inserted into both of the two.   6. The AC / DC converter according to claim 1, wherein the switching means has a switching frequency of 5 kHz or less. A first rectifier for rectifying the voltage of the AC power supply;
Smoothing means for smoothing the output voltage from the first rectifier;
Switch means disposed closer to the AC power supply than the smoothing means;
A first reactor disposed closer to the AC power supply than the switch means;
A backflow prevention diode for preventing backflow from the smoothing means to the switch means;
Control means for opening and closing the switch means;
A second reactor for suppressing a backflow current flowing from the smoothing means to the AC power supply via the backflow prevention diode during the closing operation of the switch means;
An AC / DC converter characterized by comprising:   8. The AC / DC converter according to claim 7, wherein a chopper circuit is constituted by the first reactor, the switch means, and the backflow prevention diode.   9. The AC / DC converter according to claim 8, wherein a plurality of the chopper circuits are connected in parallel.   The AC / DC converter according to claim 1, wherein the second reactor has a reactance value smaller than that of the first reactor. A DC voltage detector for detecting a DC voltage across the smoothing means; an input current detector for detecting an input current from the AC power supply;
A power supply voltage detector for detecting at least one of a voltage phase angle or a power supply voltage of the AC power supply;
With
The control means includes
Based on the detection values of the DC voltage detector, the input current detector, and the power supply voltage detector, so that the DC voltage becomes a desired constant value, and the power supply power factor is improved. The AC / DC converter according to claim 1, wherein the switch unit is opened and closed.   The AC / DC converter according to claim 1, wherein each of the semiconductor elements constituting the rectifier is formed of a wide band gap semiconductor.   The AC / DC converter according to any one of claims 1 to 12, wherein each semiconductor element constituting the switch means is formed of a wide band gap semiconductor.   The AC / DC converter according to claim 12 or 13, wherein the wide band gap semiconductor is silicon carbide, a gallium nitride-based material, or diamond. The AC / DC converter according to any one of claims 1 to 14,
An inverter that converts DC power output from the AC / DC converter into AC power;
A compressor including an electric motor driven by the inverter;
An air conditioner comprising:

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