JP2001231268A - Power conversion device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress obstruction caused by a common mode current by reducing current capacity of each noise filter. SOLUTION: Noise filters 16, 18, and 20 are inserted between an inverter 14 for converting the DC output of a rectifier 12 to a three-phase AC and a motor 12, one end of each of the noise filters 16, 18, and 20 is connected to each three-phase AC terminal of the inverter 14, and the other is connected to a motor 22. Three of noise filters 16 to 20 are connected to the output side of the inverter 14 in parallel, thus dividing the common mode current being generated from the inverter 14 by each noise filter, reducing current flowing in the noise filters 16 to 20 to 1/3, avoiding magnetic saturation, and at the same time reducing the size and weight of the noise filters 16 to 20.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power converter, and more particularly to a power converter suitable for reducing high-frequency noise (radiation noise) generated due to a common mode current when switching a high power switching element. The present invention relates to a conversion device.

[0002]

2. Description of the Related Art As power converters, converters for converting three-phase AC power to DC power and inverters for converting DC power to three-phase AC power are known. Many IGBTs (insulated gate bipolar mode transistors) that can handle large power are used. In a power converter using an IGBT as a switching element, a method of switching the IGBT at high speed is adopted. However, with the increase in the speed of switching of the IGBT, an increase in common mode current flowing to the ground through the stray capacitance of the power line and the motor has become a problem. This common mode current causes radiation noise and conduction noise, and adversely affects peripheral devices.

[0003] As a conventional technique for suppressing these obstacles,
There has been proposed one in which a common mode choke is provided in an output circuit of a voltage-type inverter (prior art 1). The common mode choke is formed by bundling a three-phase power line and winding it in a coil shape. The main current flowing from the U-phase to the V-phase and the W-phase has a low impedance characteristic because the magnetic flux cancels out the differential component. It functions as a high-impedance inductance only for the zero-phase component that is the in-phase component. Therefore, the peak value of the common mode current can be reduced by providing the common mode choke in the output circuit of the voltage type inverter.

[0004] Other conventional techniques include the Transactions of the Institute of Electrical Engineers of Japan,
D116, Vol. 12, p. 1211-1219 (1996)
As described in Japanese Unexamined Patent Application Publication No. 2000-163, a common mode transformer is proposed to reduce the common mode current by connecting a common mode transformer to the output terminal of a voltage type inverter (prior art 2). The common mode transformer is configured by winding a secondary winding around a core around which a common mode choke is wound, and connecting resistors in parallel to both ends of the secondary winding. On the primary side (power line side) of the common mode transformer, the conductors of each phase are bundled and wound in a coil shape, so that the magnetic fluxes generated by the main currents cancel each other, and no loss occurs. On the other hand, the magnetic flux linked to the secondary winding is only the magnetic flux generated by the common mode current, and the resistor connected to the secondary winding generates a loss only for the common mode current. For this reason, by connecting the common mode transformer to the output terminal of the voltage type inverter, the peak value and the effective value of the common mode current can be reduced, and high frequency vibration can be suppressed. Moreover, radioactive
Conductive electromagnetic interference can also be reduced.

Another conventional technique is disclosed in Japanese Patent Laid-Open No.
As described in JP-A-2899751, an apparatus in which two noise filters connected in parallel with each other are inserted in a DC portion between a rectifier and an inverter used in an inverter device and an air conditioner has been proposed. (Prior Art 3). According to the prior art 3, since the current capacity of each noise filter can be reduced, the size and weight of the noise filter can be reduced.

[0006]

In the prior art 1 described above,
In a small-capacity power converter, a common mode current can be effectively suppressed. However, a power converter for large power has the following problems.

(1) Since the output current is large, the core is likely to cause magnetic saturation.

(2) Since the output current is large, the cable diameter becomes large.

As a countermeasure for the above (1), there is a method in which a cut core is used and a magnetic flux is suppressed by providing a gap. However, in the configuration using the cut core, the magnetic permeability decreases. Therefore, to obtain sufficient characteristics,
It is necessary to use a large number of cores and increase the effective sectional area, which necessitates an increase in the size of the device and an increase in cost.

As a result of the above (2), it is necessary to increase the window area (area on the inner diameter side) of the core used for the common mode choke, which leads to an increase in the size of the core. In addition, since the cable diameter increases, it is extremely difficult to increase the number of turns of the coil. For this reason, in order to obtain sufficient characteristics, it is necessary to use a large number of cores, which inevitably increases the size and cost of the device.

[0011] Even when the common mode transformer of the prior art 2 is used, a small capacity power converter can effectively suppress the common mode current. However, in a large-capacity power converter, the same problem as that in the case of using the common mode choke of the related art 1 occurs.

On the other hand, when two noise filters are used as in the prior art 3, the current capacity of each noise filter can be reduced as compared with the case where a single noise filter is used. However, as the capacity of the power converter increases, the size of the noise filter must be increased.

An object of the present invention is to provide a power converter capable of further reducing the current capacity of each noise filter and suppressing a failure caused by a common mode current.

[0014]

To achieve the above object, the present invention provides a power converter for converting three-phase AC power to DC power or DC power to three-phase AC power, and a power converter for converting the three-phase AC power into three-phase AC power. A plurality of noise filters connected in series to the three-phase AC terminals of the device and having a higher impedance than a three-phase AC signal component with respect to a zero-phase component superimposed on the three-phase AC signal; The filters constitute a power converter connected in parallel with each other.

In constructing the power converter,
The same configuration can be used as the plurality of noise filters, or the number of noise filters connected in parallel can be adjusted according to the capacity of the power converter.

In configuring each of the power conversion devices, the following elements can be added.

(1) Each of the noise filters is formed of a common mode choke which is formed by bundling and winding coils of each phase connected to each of the three-phase AC terminals of the power converter.

(2) Each of the noise filters is a primary winding formed by bundling and winding a conductor of each phase connected to each of the three-phase AC terminals of the power converter and winding the core on a core, and being wound around the core. And a resistor connected in parallel to both ends of the secondary winding.

(3) Each of the noise filters uses a common resistance of the noise filters as a resistor connected in parallel to the secondary winding.

(4) Each of the noise filters is a primary winding formed by bundling and winding a conductor of each phase connected to each of the three-phase AC terminals of the power converter, and being wound around the core. One end of the secondary winding is connected to a portion corresponding to a ground potential of the power converter, and the other end of the secondary winding is connected to a power supply side or a load of the power converter. Connected to a portion corresponding to the ground potential on the side.

(5) Each of the noise filters is a primary winding formed by bundling and winding a conductor of each phase connected to each of the three-phase AC terminals of the power converter, and being wound around the core. One end of the secondary winding is connected to a portion corresponding to the ground potential of the power converter via a first common ground line common to the noise filters, The other end of the line is connected to a portion corresponding to a ground potential on the power side or the load side of the power converter via a second common ground line common to the noise filters.

(6) Each of the noise filters is a primary winding formed by bundling and winding a lead of each phase connected to each of the three-phase AC terminals of the power converter, and being wound around the core. And the secondary windings of each of the noise filters are connected in series with each other, and one of the terminals of the series-connected secondary winding that is not connected is connected to the ground of the power converter. Connected to a portion corresponding to the potential, the other of the unconnected terminals of the terminals of the secondary winding connected in series is connected to a portion corresponding to a ground potential on the power side or load side of the power converter, The turns ratio between the primary winding and the secondary winding of each noise filter is adjusted based on the number of parallel noise filters.

According to the above-described means, the common mode current generated due to the power conversion of the power converter is shunted by each noise filter to suppress the failure due to the common mode current. Can be further reduced, magnetic saturation can be avoided, and the diameter of the conductive wire constituting the noise filter can be reduced, so that the size and weight can be reduced. That is, when the diameter of the conducting wire constituting the noise filter is reduced, the number of turns of the coil can be increased. Since the magnitude of the inductance is proportional to the square of the number of turns of the coil, the number of cores can be reduced by increasing the number of turns of the coil.

Further, as the noise filter, a primary winding coil and a secondary winding coil are provided, and both ends of the secondary winding coil are connected to portions corresponding to the ground potential, respectively, so that the inside of the core is reduced. Thus, the magnetic flux linked to the magnetic field can be reduced, and the magnetic saturation can be avoided, so that the size and weight can be further reduced.

[0025]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is an overall configuration diagram of a power converter showing an embodiment of the present invention. In FIG. 1, a rectifier 12 for converting three-phase AC current to DC is connected to a three-phase AC power supply 10, and a DC output side of the rectifier 12 is a power converter for converting DC power to three-phase AC power. Are connected. This inverter 14
Is a switching element that constitutes a three-phase arm,
For example, the inverter 14 includes an IGBT and a diode connected in parallel to the IGBT.
Are connected to a motor 22 serving as a load via noise filters 16, 18, and 20.

The noise filters 16, 18, and 20
As an I (electromagnetic interference) suppression component, the zero-phase component (common mode current) superimposed on the three-phase AC signal connected in series to each of the three-phase AC terminals of the inverter 14 is more effective than the three-phase AC signal component. In this embodiment, three noise filters 1 are provided.
6, 18, and 20 are connected in parallel with each other.

When three noise filters 16, 18, and 20 are connected in parallel and inserted between the inverter 14 and the motor 12, the current flowing through each of the noise filters 16, 18, and 20 flows from the inverter 14 to the motor 22. It is 1/3 of the supplied current. When the current supplied from the inverter 14 to the motor 22 is divided by each of the noise filters 16, 18, and 20, the noise filter 16 is more effective than when the common mode current is suppressed by a single noise filter.
It is possible to reduce the cable diameter (diameter of the conducting wire) of ２０20. Therefore, when coils are used as the noise filters 16 to 20, the number of turns of the coils can be increased as compared with the case where a single noise filter is used. Since the magnitude of the inductance of the coil is proportional to the square of the number of turns of the coil, the number of cores can be reduced by increasing the number of turns of the coil.

Further, the common mode current flowing through each of the noise filters 16 to 20 can be reduced to one third as compared with the case where a single noise filter is used, so that adverse effects due to magnetic saturation can be avoided.

Further, conventionally, a noise filter is designed for each output capacity of an inverter. On the other hand, the number of noise filters 16 to 20 having the same configuration is increased as the output capacity of the inverter 14 is increased. Thus, regardless of the output capacity of the inverter 14, a noise filter having the same configuration can be used, and the cost can be significantly reduced.

Next, when constructing the noise filters 16 to 20, as shown in FIG.
Can be used.

The choke coil 24 is a U-phase cable 2 which is a conductor connected to each three-phase AC terminal of the inverter 14.
6, a V-phase cable 28 and a W-phase cable 30 are bundled and wound around the same core 32 once.

The common mode choke 24 has a U phase,
With respect to the main currents flowing in the V-phase and W-phase, the magnetic fluxes cancel each other out in the core 32, and thus have low impedance.
On the other hand, it functions as a high impedance inductance with respect to a common mode current corresponding to the in-phase zero-phase component. Therefore, by connecting the common mode choke 24 to the AC output side of the inverter 24, the peak value of the common mode current can be suppressed.

Further, by arranging three or more common mode chokes 24 in parallel, the cable diameter can be made smaller than when a single common mode choke is used, so that the number of turns of the coil can be increased. As a result, the inductance of the common mode choke 24 is greatly increased, the number of cores can be reduced, and the effect of suppressing the common mode current can be further enhanced.

Also, as the noise filters 16 to 20,
The common mode transformer 34 shown in FIG. 3 can be used. The common mode transformer 34 includes a U-phase cable 26, a V-phase cable 28, and a W-phase cable 30, which are bundled and wound once around the same core 32 to form a primary winding.
A secondary winding (secondary winding coil) 36 is wound around the secondary winding 36, and a resistor 38 is connected in parallel to both ends of the secondary winding 36. The equivalent circuit is as shown in FIG.

The common mode transformer 34 has a U-phase, V-phase
The main current flowing in the phase and the W phase has a low impedance because the magnetic fluxes cancel each other in the core 32. On the other hand, the in-phase zero-phase component acts as a transformer and supplies power to the secondary winding 36. Therefore, the resistance 3
In No. 8, loss occurs only for the common current corresponding to the zero-phase component. Thereby, the common mode transformer 34
Is connected to the output side of the inverter 14, the peak value of the common current can be suppressed.

The common mode transformer 34 can reduce both the common mode current and the magnetic flux linked to the core 32 by adjusting the resistance value of the resistor 38. Therefore, by using the common mode transformer 34, magnetic saturation can be avoided, and the common mode current can be effectively reduced with a smaller core than when the common mode choke 24 is used. Furthermore, by paralleling three or more common mode transformers 34, the inductance of each common mode transformer 34 is greatly increased, and it is possible to further reduce the number of cores and suppress the common current.

When the common mode transformers 34 are used as the noise filters 16 to 20, instead of connecting three common mode transformers 34 having the same configuration in parallel, as shown in FIG. By sharing the common mode transformer 34, the number of components can be reduced. In this case, since the resistor 38 serving as the heat generating portion can be concentrated, the heat dissipation measures can be intensively applied to the resistor 38. Further, a heat sink used for elements inside the inverter 14 and the like can be used as a heat radiation measure of the resistor 38.

Next, a PG coil (Power line & Ground line) is used as a noise filter.
An embodiment using (coil) will be described with reference to FIG.

The PG coils 40, 42, and 44 are inserted between the inverter 14 and the motor 22 as a noise filter and are connected in series to each three-phase AC output terminal of the inverter 14. , 42 and 44 are connected in parallel with each other. PG coils 40, 42, 44
As shown in FIG. 7, a U-phase cable 26, a V-phase cable 28, and a W-phase cable 30 are bundled and wound once in the form of a coil around the same core 46 to form a primary winding. One end of the ground line 48 is connected to a portion corresponding to the ground potential of the inverter 14, for example, a housing ground point of the inverter 14, and the other end of the ground line 48 Are connected to a portion corresponding to the ground potential on the load side, for example, a ground terminal 56 of the motor 22.

The PG coils 40, 42 and 44 are connected to the motor 2
It has a large inductance with respect to a common current flowing from 2 to a ground portion (earth line). On the other hand, the PG coils 40, 42, and 44 act as inductances because the magnetic fluxes generated from the respective ground lines 48 cancel each other against the common mode current flowing from the motor 22 to the inverter 14 via the ground line 48. Disappears. For this reason,
The common mode current flowing out of the motor 22 flows through the PG coils 40, 42 and 44, and is grounded (earth line).
Hardly flows to As a result, it is possible to reduce the common mode current flowing through the ground portion and acting as conduction noise.

By mounting the cables 26, 28, 30 and the ground wire 48 close to each other, radiation noise can be suppressed.

When a core having a high magnetic permeability is used as the core 46 of the PG coils 40, 42, and 44, most of the common mode current flows through the ground line 48.
Few magnetic fluxes are generated in 6. Therefore, core 4
6 can be made smaller than the cores of the common mode choke 24 and the common mode transformer 34, so that reduction in size and weight and cost can be achieved. Further, by increasing the number of PG coils and paralleling three or more, the inductance of each coil is greatly increased, and the number of cores can be further reduced and the common mode current can be suppressed.

In the embodiment shown in FIG.
One of the ground wires 48 of 0, 42, and 44 is connected to the ground terminal 56 of the motor 22. The input portion of the motor 22 is star-connected using an impedance such as a capacitor, and a ground wire is connected to the neutral point. A similar effect can be obtained by employing a configuration in which one of the 48 is connected.

In the embodiment shown in FIG. 6, the other of the ground lines 48 of the PG coils 40, 42, and 44 is connected to the inverter 1
4, a neutral point obtained by dividing the DC side of the inverter 14 by impedance such as a capacitor, one of an anode and a cathode on the DC side of the inverter 14, or a three-phase AC power supply 10 A similar effect can be obtained by connecting the power supply to a neutral point star-connected using the impedance of a capacitor or the ground terminal of the three-phase AC power supply 10.

Next, another embodiment using a PG coil will be described with reference to FIG. In the present embodiment, both ends of a ground wire 48 of a PG coil 40, 42, 44 as a noise filter are connected to each other, and this connection point is connected to a housing ground point of the inverter 14 via a first common ground line 58, and the other end. Is connected to the ground terminal 56 of the motor 22 via the second common ground line 60, and the other configuration is the same as that of FIG.

In this embodiment, the common ground line 58,
Since the ground wire 48 is shared by using 60, the length of the ground wire 48 is shortened, and when the distance between the inverter 14 and the motor 22 is long, the size and weight can be reduced and the size and weight can be reduced more than in the above-described embodiment. Cost reduction becomes possible.

Next, another embodiment in which a PG coil is used as a noise filter will be described with reference to FIG.

In this embodiment, the PG coils 40, 42, 4
4 of the PG coil 40
Of the terminals of the ground line 48 of the inverter 1
4 and the ground wire 48 of the PG coil 44.
Of the unconnected terminals are connected to the ground terminal 56 of the motor 22.
To each of the PG coils 40, 42, and 44.
The turns ratio between the secondary winding and the secondary winding is determined by the PG coils 40, 42,
It is adjusted according to 44 parallel numbers (3),
Other configurations are the same as those in FIG.

According to the present embodiment, the common mode current is divided as in the embodiment shown in FIG.
Disturbance of radiation noise generated by the common mode current can be suppressed, and reduction in size and weight and cost can be achieved. Further, since the ground wires 48 are connected in series with each other, the length of the ground wire 48 can be shortened, and the size, weight, and cost can be further reduced as compared with the above embodiment.

In the embodiment shown in FIGS. 6 to 9, P
Although the description has been given of the case where the G coils 40, 42, and 44 are applied to the three-phase inverter 14, the same effect can be obtained by applying the PG coil to the single-phase inverter.

In each of the above embodiments, the case where the inverter 14 is used as the power converter has been described. However, the present invention can be applied to a converter. When the present invention is applied to a converter as a power converter, by inserting a noise filter between the power supply and the converter, it is possible to obtain the same effect as when the inverter 14 is applied.

[0052]

As described above, according to the present invention,
Each noise filter shunts the common mode current generated by the power converter's power conversion to suppress the failure caused by the common mode current, so the current capacity of each noise filter can be further reduced, and the magnetic saturation can be reduced. Can be avoided, and the diameter of the conductive wire constituting the noise filter can be reduced, so that the size and weight can be reduced.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of a power converter showing an embodiment of the present invention.

FIG. 2 is a configuration diagram of a common mode choke.

FIG. 3 is a configuration diagram of a common mode transformer.

FIG. 4 is an equivalent circuit diagram of a common mode transformer.

FIG. 5 is an equivalent circuit diagram showing another embodiment of the common mode transformer.

FIG. 6 is an overall configuration diagram showing an embodiment when a PG coil is used.

FIG. 7 is a configuration diagram of a PG coil.

FIG. 8 is an overall configuration diagram showing another embodiment using a PG coil.

FIG. 9 is an overall configuration diagram showing still another embodiment using a PG coil.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Three-phase alternating current power supply 12 Rectifier 14 Inverter 16, 18, 20 Noise filter 22 Motor 24 Common mode choke 26 U-phase cable 28 V-phase cable 30 W-phase cable 32 Core 34 Common mode transformer 36 Secondary winding 38 Resistance 40, 42 , 44 PG coil 46 core 48 ground line 56 ground terminal 58 first common ground line 60 second common ground line

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5G066 EA01 5H007 AA01 BB06 CA01 CB00 CC09 HA02 5H740 BA11 BB09 BB10 NN02 NN17 PP10

Claims (9)

[Claims] 1. A power converter for converting three-phase AC power into DC power or DC power into three-phase AC power, and a three-phase AC signal connected in series to each three-phase AC terminal of the power converter. And a plurality of noise filters each having a higher impedance than a three-phase AC signal component with respect to a zero-phase component superimposed on the plurality of noise filters, wherein the plurality of noise filters are connected in parallel with each other. 2. A power converter for converting three-phase AC power into DC power or converting DC power into three-phase AC power, and a three-phase AC signal connected in series to each three-phase AC terminal of the power converter. A plurality of noise filters that have a higher impedance than a three-phase AC signal component with respect to the zero-phase component superimposed on the power supply device, wherein the plurality of noise filters have the same configuration and are connected in parallel with each other. . 3. A power converter for converting three-phase AC power into DC power or converting DC power into three-phase AC power, and a three-phase AC signal connected in series to each three-phase AC terminal of the power converter. A plurality of noise filters having a higher impedance than a three-phase AC signal component with respect to a zero-phase component superimposed on the noise filter, wherein the plurality of noise filters are connected in parallel with each other, and the number of noise filters connected in parallel Is a power converter that is adjusted according to the capacity of the power converter. 4. Each of the noise filters is configured by a common mode choke formed by bundling and winding a coil of each phase connected to each three-phase AC terminal of the power converter. The power converter according to claim 1, 2 or 3, wherein: 5. A primary winding formed by bundling and winding a core of each phase connected to each three-phase AC terminal of the power converter and wound around a core, and each of the noise filters is wound around the core. 4. The power converter according to claim 1, further comprising a secondary winding and a resistor connected in parallel to both ends of the secondary winding. 6. The power converter according to claim 5, wherein each of said noise filters uses a resistor common to each of said noise filters as a resistor connected in parallel to said secondary winding. 7. Each of the noise filters is a primary winding formed by bundling and winding a conductor of each phase connected to each of the three-phase AC terminals of the power converter, and being wound around the core. A secondary winding, one end of the secondary winding is connected to a portion corresponding to a ground potential of the power converter, and the other end of the secondary winding is connected to a power supply side or a load side of the power converter. 4. The power conversion device according to claim 1, wherein the power conversion device is connected to a portion corresponding to a ground potential. 8. Each of the noise filters is a primary winding formed by bundling and winding a conductor of each phase connected to each of the three-phase AC terminals of the power converter, and being wound around the core. A secondary winding, and one end of the secondary winding is connected to a portion corresponding to a ground potential of the power converter via a first common ground line common to the respective noise filters, The other end of the power converter is connected to a portion corresponding to a ground potential on a power supply side or a load side of the power converter via a second common ground line common to the respective noise filters. Or the power converter according to 3. 9. Each of the noise filters is a primary winding formed by bundling and winding a conductor of each phase connected to each of the three-phase AC terminals of the power converter, and being wound around the core. And a secondary winding of each noise filter is connected in series with each other, and one of the terminals of the series-connected secondary winding that is not connected is connected to the ground potential of the power converter. The other of the unconnected terminals of the terminals of the secondary windings connected in series is connected to a portion corresponding to the ground potential on the power side or the load side of the power converter, 4. The power converter according to claim 1, wherein a turn ratio between a primary winding and a secondary winding of the noise filter is adjusted based on the number of parallel noise filters.