WO2021106081A1

WO2021106081A1 - Power converter

Info

Publication number: WO2021106081A1
Application number: PCT/JP2019/046190
Authority: WO
Inventors: 村上　哲
Original assignee: 三菱電機株式会社
Priority date: 2019-11-26
Filing date: 2019-11-26
Publication date: 2021-06-03
Also published as: JPWO2021106081A1; JP7130151B2

Abstract

This power converter (100) is provided with a power converter circuit (20) and a noise cancelling circuit (30). The noise cancelling circuit (30) is provided with: a first reactor (31a) which is serially inserted in a direct-current bus bar (21P); a transformer (32a) which has two reverse-coupled windings connected to each other at a winding connection point (36a); second and third reactors (33a1, 33a2) which are respectively connected at portions between first and second ends of the first reactor (31a) and the respective windings of the transformer (32a); and first and second coupling capacitors (34a, 35a) which allow only an alternating-current component to pass therethrough. Further, the winding connection point (36a) of the transformer (32a) is grounded via the first coupling capacitor (34a), and at the same time, is connected to a shielded wire (12A) of a power supply cable (10) via the second coupling capacitor (35a).

Description

Power converter

This application relates to a power conversion device.

Since common mode noise is generated in the power conversion device due to the on / off operation of the switching element, it has been conventionally proposed to include a noise canceling circuit.
A conventional power converter includes an LC filter having a filter reactor inserted in series with a DC bus and a two-series filter capacitor connected between the DC buses, and provides a mutual connection point between the two series filter capacitors. Earth. In addition, the noise canceling circuit uses the ripple voltage or ripple current generated between the smoothing capacitor provided between the LC filter and the power conversion circuit and the ground to make the ripple current almost equal to the ripple current flowing through the filter reactor. A current of opposite phase is generated and injected into the DC power supply side terminal of the filter reactor (see, for example, Patent Document 1).

Japanese Unexamined Patent Publication No. 5-219758 (paragraphs [0017] to [0021], FIG. 6)

The conventional power conversion device is equipped with an LC filter and a noise canceling circuit, so that the circuit configuration becomes large. In addition, it is difficult to miniaturize the filter reactor itself of the LC filter. Further, if the ripple current remains without being canceled ideally, the common mode noise current leaks to the power cable, causing a problem that common mode noise is generated.

The present application discloses a technique for solving the above-mentioned problems, and an object of the present application is to provide a power conversion device capable of suppressing common mode noise and promoting miniaturization of a device configuration.

The power conversion device disclosed in the present application includes a DC bus connected to a power cable, a power conversion circuit using the DC bus as an input / output line, and a common mode noise current flowing through the power cable via the DC bus. It is equipped with a noise canceling circuit that suppresses the noise. In the noise canceling circuit, a first reactor inserted in series with the DC bus, a primary winding and a secondary winding are inversely coupled, and each first end is connected to each other at a winding connection point. The transformer, the second reactor connected between the first end of the first reactor and the second end of the primary winding, the second end of the first reactor and the second end of the secondary winding. A third reactor connected to the transformer and first and second coupling capacitors through which only an AC component is passed are provided, and the winding connection point of the transformer is grounded via the first coupling capacitor. At the same time, it is connected to the shielded wire of the power cable via the second coupling capacitor.

According to the power conversion device disclosed in the present application, it is possible to suppress common mode noise and promote miniaturization of the device configuration.

It is a figure which shows the schematic structure of the power conversion apparatus according to Embodiment 1. It is a circuit diagram explaining the operation of the noise canceling circuit by Embodiment 1. FIG. It is a waveform diagram of each part explaining the operation of the noise canceling circuit by Embodiment 1. FIG. It is a waveform diagram of each part explaining the operation of the noise canceling circuit by Embodiment 1. FIG. It is a figure explaining the effect of the noise canceling circuit by Embodiment 1. FIG. It is a figure which shows the schematic structure of the power conversion apparatus by another example of Embodiment 1. It is a figure which shows the schematic structure of the power conversion apparatus according to Embodiment 2.

Embodiment 1.
FIG. 1 is a diagram showing a schematic configuration of a power conversion device according to a first embodiment.
As shown in the figure, the power conversion device 100 is connected to the DC voltage source 2 in the power supply circuit 1 via the power supply cable 10.
The power cable 10 is composed of a cable wire 11P on the positive electrode side and a shielded wire 12A of the cable wire 11P, and a cable wire 11N on the negative electrode side and a shielded wire 12B of the cable wire 11N. A stray capacitance 13a is formed between the cable wire 11P on the positive electrode side and the shielded wire 12A, and a stray capacitance 13b is formed between the cable wire 11N on the negative electrode side and the shielded wire 12B.
The shielded

wires

12A and 12B are not grounded.
Further, the shielded

wires

12A and 12B may be configured by a common shielded wire.

The power conversion device 100 includes positive and

negative DC bus

21P and 21N connected to the power cable 10, a power conversion circuit 20 having

DC bus

21P and 21N as input / output lines, and a noise canceling circuit 30.
The DC bus 21P is connected to the cable line 11P, and the DC bus 21N is connected to the cable line 11N. The power conversion circuit 20 converts the DC power from the DC voltage source 2 into DC power or AC power and outputs the power to a load (not shown). The noise canceling circuit 30 suppresses common mode noise generated due to the switching operation in the power conversion circuit 20.

In the noise canceling circuit 30, the positive electrode side circuit 30A and the negative electrode side circuit 30B are configured in the same manner, and the noise current in the common mode flowing through the power cable 10 via the positive and

negative DC bus

21P and 21N is suppressed.
The positive electrode side circuit 30A of the noise canceling circuit 30 passes only the first reactor 31a, the transformer 32a, the second and third reactors 33a1 and 33a2 inserted in series with the DC bus 21P, and the first and first AC components. 2

Coupling capacitors

34a and 35a are provided.

In the transformer 32a, the primary winding 32aP and the secondary winding 32aS are inversely coupled, and the primary winding 32aP and the secondary winding 32aS are connected to each other at the winding connection point 36a. In this case, the winding ratio of the primary winding 32aP and the secondary winding 32aS is 1: 1.
Further, the second reactor 33a1 is connected between the first end of the first reactor 31a on the power conversion circuit 20 side and the primary winding 32aP, and between the second end of the first reactor 31a and the secondary winding 32aS. The third reactor 33a2 is connected to the third reactor 33a2. In this case, elements having the same configuration are used for the second reactor 33a1 and the third reactor 33a2.
The winding connection point 36a is grounded via the first coupling capacitor 34a and is connected to the shielded wire 12A of the cable wire 11P via the second coupling capacitor 35a.

The negative electrode side circuit 30B of the noise canceling circuit 30 passes only the first reactor 31b, the transformer 32b, the second and third reactors 33b1 and 33b2 inserted in series with the DC bus 21N, and the first and first AC components. 2

Coupling capacitors

34b and 35b are provided.
In the transformer 32b, the primary winding 32bP and the secondary winding 32bS are inversely coupled, and the primary winding 32bP and the secondary winding 32bS are connected to each other at the winding connection point 36b. In this case, the winding ratio of the primary winding 32bP and the secondary winding 32bS is 1: 1.

Further, the second reactor 33b1 is connected between the first end of the first reactor 31b on the power conversion circuit 20 side and the primary winding 32bP, and between the second end of the first reactor 31b and the secondary winding 32bS. The third reactor 33b2 is connected to the third reactor 33b2. In this case, the second reactor 33b1 and the third reactor 33b2 use elements having the same configuration.
The winding connection point 36b is grounded via the first coupling capacitor 34b and is connected to the shielded wire 12B of the cable wire 11N via the second coupling capacitor 35b.

The

first reactors

31a and 31b inserted in series with the positive and

negative DC bus

21P and 21N may be configured by using a common mode choke coil.

FIG. 2 is a circuit diagram illustrating the operation of the noise canceling circuit 30 (positive electrode side circuit 30A). As described above, the noise canceling circuit 30 has the same circuit configuration on the positive electrode side and the negative electrode side, and operates in the same manner. Hereinafter, the description will be made using the positive electrode side circuit 30A, and the description of the negative electrode side circuit 30B will be omitted as appropriate.
The first and

second coupling capacitors

34a and 35a remove the DC component and allow only the AC component to pass through. Further, the first coupling capacitor 34a is used to prevent a short circuit, and the second coupling capacitor 34a is used to prevent an electric shock.
The shielded wire 12A of the cable wire 11P is not directly grounded, but is grounded via the first coupling capacitor 34a and the second coupling capacitor 35a.

Point A in the noise canceling circuit 30 indicates a connection point between the first reactor 31a and the second reactor 33a1, and point B indicates a connection point between the first reactor 31a and the third reactor 33a2. Point C1 indicates the connection point between the second reactor 33a1 and the primary winding 32aP of the transformer 32a, and point C2 indicates the connection point between the third reactor 33a2 and the secondary winding 32aS of the transformer 32a. Further, the point D indicates a point where the winding connection point 36a, the first coupling capacitor 34a, and the second coupling capacitor 35a are connected.

The current Iin indicates the current input to the noise canceling circuit 30, and the current IL indicates the current flowing from the point A to the point B in the noise canceling circuit 30, that is, the current flowing through the first reactor 31a. The current IP indicates the current flowing from the point A to the point D in the noise canceling circuit 30, and the current IS indicates the current flowing from the point B to the point D in the noise canceling circuit 30. The current Iout indicates the current that cannot be completely removed by the noise canceling circuit 30 and is output from the point B to the cable line 11P via the DC bus 21P.
The currents Iin, IL, IP, and IS are common mode noise currents.

The current IP and the current IS are currents of the same phase and both flow from the point D to the ground via the first coupling capacitor 34a. As shown in FIG. 2, since the DC bus 21P has a stray capacitance 50 with the ground, the current IP and the current IS return from the ground to the adjacent DC bus 21P via the stray capacitance 50. Therefore, common mode noise does not leak to the external environment.

FIG. 3 is a waveform diagram of each part for explaining the operation of the noise canceling circuit 30.
In this case, the impedance of the second reactor 33a1 and the impedance of the third reactor 33a2 are equal, and the impedance of the first reactor 31a is twice the impedance of the second and third reactors 33a1 and 33a2. That is, the impedance ratio of the first reactor 31a, the second reactor 33a1 and the third reactor 33a2 is 2: 1: 1.
At this time, the current IL, the current IP, and the current IS are currents having the same phase and amplitude. Therefore, the voltage between AC1 and V-AC1, the voltage between B and C2, V-BC2, and the voltage between C1-D, V-C1D, are equal to each other.

Since the primary winding 32aP and the secondary winding 32aS of the transformer 32a are inversely coupled and the winding ratio is 1: 1, the primary winding 32aP and the secondary winding 32aS have the same size in opposite phases. A voltage is generated. Therefore, V-C2D, which is the voltage between C2-D, has the same magnitude as V-C1D in the opposite phase.
As for V-BC2 and V-C2D, the voltages have the same magnitude in opposite phases, and V-BD, which is the voltage between BD, becomes 0 voltage. As a result, the current Iout does not flow.
Further, V-AD, which is the voltage between A and D, and V-AB, which is the voltage between AB, are equal to each other.

In this way, the noise canceling circuit 30 sets V-BD, which is a common mode voltage output to the cable line 11P, to 0 voltage, that is, between the second end of the first reactor 31a and the winding connection point 36a. It operates so that the voltage difference becomes 0 voltage. As shown in FIG. 3, when the noise canceling circuit 30 ideally operates and the V-BD reaches 0 voltage, all the noise currents Iin input to the noise canceling circuit 30 are canceled and the current Iout is not output.

Next, the case where the noise canceling circuit 30 cannot completely remove the input noise current Iin and the current Iout is output will be described. FIG. 4 is a waveform diagram of each part for explaining the operation of the noise canceling circuit 30.
In this case, it is assumed that the impedance ratios of the first reactor 31a, the second reactor 33a1 and the third reactor 33a2 deviate from the ideal state, for example, 1.6: 1: 1.
At this time, the current IL ≠ the current IS (= current IP), and (V-AC1) = (V-BC2) ≠ (V-C1D). Since V-C2D and V-C1D have opposite phases and the same voltage, V-BC2 and V-C2D have opposite phases and different voltages, and V-BD does not have 0 voltage. Also, V-AD and V-AB do not match.

In this way, the noise canceling circuit 30 outputs the common mode voltage V-BD (≠ 0) to the cable line 11P, and outputs the current Iout (≠ 0).
Then, as shown in FIG. 2, the current Iout output from the point B in the noise canceling circuit 30 has a DC bus 21P, a cable wire 11P, a stray capacitance 13a, a shielded wire 12A, a second coupling capacitor 35a, and a transformer 32a. Circulates through the secondary winding 32aS and the third reactor 33a2.

In this way, the circulating current (current Iout) is passed through the DC bus 21P, the cable wire 11P, the floating capacitance 13a, the shielded wire 12A, the second coupling capacitor 35a, the secondary winding 32aS of the transformer 32a, and the third reactor 33a2. The current path 40 through which the current flows is formed, and the current Iout becomes a circulating current circulating in the current path 40. Therefore, the current Iout becomes a normal mode current having different properties from the common mode noise current, and as a result, the common mode noise current is completely removed by the noise canceling circuit 30 and is not output.

The positive electrode side circuit 30A of the noise canceling circuit 30 has been described above, but the negative electrode side circuit 30B also operates in the same manner and the same result can be obtained.

Since the power conversion device 100 according to this embodiment is configured as described above, common mode noise can be suppressed without using an LC filter in the noise canceling circuit 30, and miniaturization of the device configuration can be promoted. In particular, the

first reactors

31a and 31b inserted into the

DC bus

21P and 21N need to be smaller than the reactor in the LC filter, and the common mode noise can be suppressed only by the small noise canceling circuit 30. Become.

FIG. 5 is a diagram for explaining the effect of the noise canceling circuit 30, and shows the voltage amplitude response characteristic with respect to the frequency. The input voltage Vin of the noise canceling circuit 30 corresponds to V-AD, and the output voltage Vout corresponds to V-BD. As shown by the characteristic line 60 showing the voltage amplitude response, the noise canceling circuit 30 can reduce the common mode voltage widely from the low frequency band to the high frequency band.
On the other hand, in the comparative example using the LC filter widely used conventionally, as shown by the comparative characteristic line 61 showing the voltage amplitude response, almost no effect is seen in the low frequency band.

Further, in this embodiment, even if the noise canceling circuit 30 cannot completely remove the noise current and outputs the current Iout to the

cable lines

11P and 11N, the current Iout floats between the cable line 11P and the shielded wire 12A. It circulates in the current path 40 formed through the capacitance 13a. Therefore, the current Iout output from the noise canceling circuit 30 becomes a current changed from the common mode to the normal mode, and the effect of suppressing the common mode noise is remarkably improved.

Further, in this embodiment, even if the noise canceling circuit 30 does not operate ideally and the current Iout is output, common mode noise due to the current Iout does not occur. Therefore, the power conversion device 100 including the noise canceling circuit 30. Increases design freedom.

In the above embodiment, the power conversion device 100 is connected to the DC voltage source 2 in the power supply circuit 1 via the power supply cable 10, but as shown in FIG. 6, it is connected to the DC load 4 in the load circuit 3. It may be connected via the power cable 10.
Also in this case, the noise canceling circuit 30 operates in the same manner as in the above embodiment, and the power conversion device 100 obtains the same effect.

Embodiment 2.
FIG. 7 is a diagram showing a schematic configuration of the power conversion device according to the second embodiment.
As shown in FIG. 7, in the second embodiment, the noise canceling circuit 30C omits the second actuators 33a1, 33b1 and the third inductance 33a2, 33b2 shown in the first embodiment, and omits the

transformers

32a, 32b. Use the leakage inductance of.
That is, the second reactor 33a1 and the third reactor 33a2 shown in the first embodiment are composed of the leakage inductance of the transformer 32a, and the second reactor 33b1 and the third reactor 33b2 are composed of the leakage inductance of the transformer 32b. Other configurations are the same as those in the first embodiment.

The noise canceling circuit 30C according to this embodiment operates in the same manner as in the first embodiment, and the same effect can be obtained. Further, since the second reactors 33a1 and 33b1 and the third reactors 33a2 and 33b2 can be omitted, the miniaturization of the power conversion device 100 can be further promoted.

Although the present application describes various exemplary embodiments and examples, the various features, embodiments, and functions described in one or more embodiments are applications of a particular embodiment. It is not limited to, but can be applied to embodiments alone or in various combinations.
Therefore, innumerable variations not illustrated are envisioned within the scope of the techniques disclosed in the present application. For example, it is assumed that at least one component is modified, added or omitted, and further, at least one component is extracted and combined with the components of other embodiments.

10 Power cable, 11P, 11N cable line, 12A, 12B shielded wire, 13a, 13b stray capacitance, 20 power conversion circuit, 21P, 21N DC bus, 30,30C noise canceling circuit, 31a, 31b first reactor, 32a, 32b Transformer, 32aP, 32bP primary winding, 32aS, 32bS secondary winding, 33a1, 33b1 second reactor, 33a2, 33b2 third reactor, 34a, 34b first coupling capacitor, 35a, 35b second coupling capacitor, 36a , 36b Winding connection point, 40 current path, 100 power converter.

Claims

The DC bus connected to the power cable and
A power conversion circuit using the DC bus as an input / output line and
A noise canceling circuit that suppresses a common mode noise current flowing through the power cable via the DC bus is provided.
The noise canceling circuit
The first reactor inserted in series with the DC bus and
A transformer in which the primary winding and the secondary winding are inversely coupled and their first ends are connected to each other at the winding connection point.
A second reactor connected between the first end of the first reactor and the second end of the primary winding,
A third reactor connected between the second end of the first reactor and the second end of the secondary winding,
Equipped with first and second coupling capacitors that allow only AC components to pass through,
The winding connection point of the transformer is grounded via the first coupling capacitor and connected to the shielded wire of the power cable via the second coupling capacitor.
Power converter.
Via the DC bus, the power cable, the stray capacitance between the power cable and the shielded wire, the shielded wire, the second coupling capacitor, the secondary winding of the transformer, and the third reactor. A current path through which circulating current flows is formed,
The power conversion device according to claim 1.
The noise canceling circuit connects the noise current flowing to the ground through the primary winding of the transformer and the first coupling capacitor, and the noise current flowing to the ground via the secondary winding of the transformer and the first coupling capacitor. It operates so that the flowing noise current is in phase with each other and the voltage difference between the second end of the first reactor and the winding connection point is set to 0 voltage.
The power conversion device according to claim 1 or 2.
The first reactor is composed of a common mode choke coil.
The power conversion device according to any one of claims 1 to 3.
The winding ratio of the primary winding to the secondary winding of the transformer was set to 1: 1.
The power conversion device according to any one of claims 1 to 4.
The impedance of the second reactor is equal to the impedance of the third reactor.
The power conversion device according to claim 5.
The impedance ratio of the first reactor, the second reactor and the third reactor is 2: 1: 1.
The power conversion device according to claim 6.
The second reactor and the third reactor are composed of the leakage inductance of the transformer.
The power conversion device according to any one of claims 1 to 7.