JP2000201044A - Common mode noise reducing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a common mode noise reducing device for surely reducing the high frequency components of a common mode voltage even when the power supply voltage of a buffer type amplifier is set to a further low value. SOLUTION: This device is provided with a common mode voltage detecting circuit 15 for detecting the common mode voltage of an AC cable way as a common mode voltage compensating circuit, a common mode transformer CT1 equipped with wirings W1, W2, and W3 serially inserted into each phase of the AC cable way and a wiring 4 magnetically engaged with those wirings, a low pass filter 13 for operating by inputting a common mode voltage from the common mode voltage detecting circuit 15 through a complementary buffer amplifier AP1, and a complementary buffer amplifier AP2 for operating by inputting the output of the low pass filter 13. Then, the output difference of the complementary buffer amplifiers AP1 and AP2 is applied to the wiring W4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to noise reduction based on an inverter device or the like, and more particularly to a common mode noise for suppressing a common mode voltage and a common mode current leaking from a load driven at a variable speed by an inverter. It relates to a suppression device.

[0002]

2. Description of the Related Art FIG. 14 is, for example, a document of the Semiconductor Power Conversion Study Group published in January 1998 (SPC-98-43), "Active Compensation Circuit for Common Mode Voltage of Large Capacity PWM Inverter", pp. 63-68. 1 is a diagram showing a conventional device described in FIG.
Is a voltage type inverter including a diode bridge circuit 7, a DC capacitor C1 for smoothing, and an inverter circuit 8,
Is a common mode voltage compensation circuit, 4 is an output cable, 5 is a three-phase motor, 6 is a ground point, and 9 is the voltage type inverter 2
And Z1 to Z5 are floating impedances, each of which mainly corresponds to a floating capacitor. Reference numeral 14 denotes a frame of the three-phase electric motor 5, which is connected to the ground point 6. The inverter circuit 8 converts a DC voltage into a three-phase AC voltage by a semiconductor switch controlled by, for example, pulse width modulation. The voltage type inverter 2 and the three-phase motor 5 are connected to a ground point 6 to prevent a danger of electric shock. In the common mode voltage compensation circuit 30, C10 to C16 are capacitors, T10
T13 is a transistor, 31 and 32 are DC power supplies, CT
5 is a common mode transformer having windings W7 to W10. A high-pass filter is formed by the resistor R2 and the capacitor C16.

Next, the common mode voltage generated by the voltage type inverter 2 will be described. FIG. 15 is a waveform diagram showing one section of the PWM triangular wave carrier frequency (switching frequency). In FIG. 15, (a) is a waveform of a U-phase voltage which is an output voltage of the voltage type inverter 2, and (b) is the same. The waveform of the V-phase voltage, (c) is also the waveform of the W-phase voltage, and a pulse-like voltage as shown in FIG. 15 is generated according to the command of the voltage to be output from the inverter circuit 8. The magnitude of each pulse is the voltage Vd across the capacitor C1 in FIG. On the other hand, the common mode voltage v0 generated on the load side by the voltage type inverter 2 by the pulse is given as shown in FIG. 3D, and the voltage step width is (1/3) * Vd according to the relationship of the equation (1). Becomes v0 = (vU + vV + vW) / 3 (1) In FIG. 16, reference numeral 200 denotes a source of the common mode voltage v0, Z101 denotes a floating impedance with respect to a ground point 6 on the output side of the voltage type inverter 2, and Z100 denotes a voltage type inverter. Assuming that the floating impedance with respect to the grounding point 6 at the input side of FIG.
A step-like voltage as shown in (d) is applied. Therefore, a high-frequency common mode current flowing through the above two floating impedances, and electromagnetic noise due to the high frequency common mode current are generated. In FIG. 14, an actual common mode current path includes a floating impedance Z2 existing between the diode bridge circuit 7 and the heat sink 9 connected to the ground line PE, and a floating impedance Z2 existing between the inverter circuit 8 and the heat sink 9. Impedance Z3,
Represented by a floating impedance Z4 existing between the output cable 4 and the ground line PE, and a floating impedance Z5 existing between the three-phase input point of the three-phase motor 5 and the motor frame 14 connected to the ground line PE; These all have capacitive characteristics.

Next, the operation of the above conventional example will be described.
The common mode voltage appearing at the output of the voltage type inverter 2 is detected and divided by the capacitors C12 to C15. The potential reference point of the common mode voltage compensation circuit 30 is obtained by the capacitors C10 and C11. The two complementary buffer amplifiers AP1 and AP2 constituted by the transistors T10 to T13 are for preventing mutual effects between the high-pass filters C16 and R2, the common mode voltage and the common mode transformer CT5. Voltages are supplied to the complementary buffer amplifiers AP1 and AP2 by DC power supplies 31 and 32. The common mode voltage compensating circuit 30 filters the common mode voltage with a high-pass filter composed of a capacitor C16 and a resistor R2, and then applies the filtered voltage to a high-frequency common mode transformer CT5, and the inverter of each phase. The filtered voltage is applied to the output to cancel the high frequency component of the common mode voltage. That is, here is harmful noise, for example, 1
The high frequency range of 50 KHz to 30 MHz is to be compensated, and the low frequency component of the common mode voltage is not to be compensated. Thus, the common mode voltage compensating circuit 30 is connected to the X, Y, Z
The inclination of the common mode voltage in the terminal voltage is suppressed, whereby the current flowing through the floating impedance existing between the output cable 4 and the three-phase motor 5 and the ground is suppressed, and the common mode current flowing through the system power supply 1 is suppressed. be able to.

FIG. 17 shows, for example, the 1997 National Conference of the Industrial Applications Division of the Institute of Electrical Engineers of Japan, FIG. 80 is a diagram showing another conventional device described in “Application of Active EMI Filter to Air Conditioner”, pp. 181 to 182, and FIG.
Is a common mode current compensation circuit, and the common mode current Ic10 on the input side of the voltage type inverter 2 is detected by the high frequency common mode transformer CT6 in the common mode current compensation circuit 33. The secondary-side current Ic11 of the high-frequency common-mode transformer CT6, which is a detected value of the common-mode current, is amplified by a current amplifier including the transistors T14 and T15 and the resistor R3. The current Ic12 thus amplified is supplied to the capacitor C1
7. The current flows through the current amplifier, the DC capacitor C1, the inverter circuit 8, and the three-phase motor 5. In this way, the current Ic12 is controlled to have an amplified value of Ic10, so that the leakage current Ic13 of the three-phase motor 5 is controlled.
Of the common mode current Ic10 flowing through the three-phase system power supply 1 is suppressed. Therefore, the value of the common mode current Ic10 decreases as the current amplification coefficient (Ic12 / Ic10) increases.

FIG. 18 is a diagram showing another conventional apparatus described in, for example, Japanese Patent Application Laid-Open No. 9-37593. In the figure, reference numeral 34 denotes a common mode current compensation circuit. The common mode current caused by the common mode voltage of the voltage type inverter 2 is a floating capacitor C18 between the power semiconductor of the inverter circuit 8 and the heat sink 9, and a floating capacitor C1 between the input terminal of the three-phase motor 5 and the ground line PE.
Flow through 9. To compensate for these common mode currents, two capacitors C20 and C21 are connected to C2
0 capacitance value = C18 capacitance value, C21 capacitance value = C19
Are connected so that the capacitance value becomes The capacitors C20 and C21 are connected to a variable voltage source 35. The variable voltage source 35 detects a common mode voltage of the inverter and generates a voltage at terminal a that cancels the common mode voltage. As a result, Ic20 = −Ic18, I
c21 = −Ic19, and the common mode currents Ic23 and Ic22 flowing through the three-phase system power supply 1 are suppressed.

[0007]

First, in the conventional device shown in FIG. 14, since the object of suppression compensation is the high-frequency component of the common mode voltage as described above, C1
The high-frequency components are extracted by the high-pass filters C16 and R2 from the output of the common mode voltage detected by 2 to C15, and the output is applied to the winding W10 of the common mode transformer CT5. Complementary buffer amplifiers AP1 and AP2 are provided before and after this high-pass filter in order to prevent mutual influence with the input and output terminals. From the above configuration, there is a problem that the suppression compensation of the common mode voltage may not be reliably performed. Hereinafter, this phenomenon will be described in detail.

FIG. 19 shows this compensation circuit portion. In the drawing, M1 and M2 are devices for measuring a common mode voltage of a three-phase line for explanation. FIG.
0 is a diagram showing the result of compensating for the common mode voltage using the conventional high-pass filter. In the figure, the horizontal axis is the time axis, (a) is the common mode voltage v0 in the three-phase motor 5 generated by the inverter circuit 8, and (b) is FIG.
9, the output voltage v3 of the high-pass filter 20;
(C) is an output voltage v4 of the complementary buffer amplifier AP2,
(D) is the compensated common mode voltage v7, v0,
v3, v4, and v7 are all normalized by 1/2 and Vd / 2 of the DC voltage Vd of the DC capacitor C1 of the voltage type inverter 2. Each of the three patterns arranged in the horizontal direction shows a typical waveform of the common mode voltage v0, and the pattern at the left end in FIG. 15 is the one illustrated in FIG. That is, the common mode voltage v0 of this pattern is such that the height of the rising and falling steps is １ ／ of the DC voltage Vd.
Becomes The other two patterns have a step height larger than Vd / 3.

As shown in FIG. 14, the high-pass filter includes, for example, a capacitor C16 inserted in series between input and output terminals and a resistor R2 connected in parallel to the output terminal. So, of course,
When a step-like voltage v0 as shown in FIG. 20A is input to the high-pass filter, the output voltage v3 becomes
From the zero level, once rise (or fall) to the peak value corresponding to the step height.

Incidentally, in the conventional device illustrated in FIG. 14, the complementary buffer amplifier AP2 includes DC power supplies 31, 3
2 and a single-ended push-pull circuit composed of transistors T12 and T13.
2 can only output an amplitude up to ± 50 V. on the other hand,
Since the voltage Vd of the DC capacitor C1 of the voltage-type inverter 2 is 280 V, the common mode voltage v0 having a step height up to 1/3 (280/3 ≒ 93.3 V) can be output. If the height exceeds the above value, the output voltage will be limited.

FIG. 20C shows this state.
In the case of the common mode voltage v0 at which the step height at the left end is Vd / 3, the output waveform v4 of the high-pass filter has no distortion, but the step height exceeds Vd / 3, and the common mode shown at the center and right end in FIG. In the case of the voltage v0, as shown by a circle in the figure, the peak value of the output voltage v4 of the high-pass filter is limited by the voltages of the DC power supplies 31 and 32, and the waveform is distorted from the original high-pass filter output waveform. As a result, the voltage v7 compensated based on the voltage v4
As shown by a circle in FIG. 4D, there is a steep waveform portion that is not substantially compensated and contains a high-frequency component, so that the common mode current can be completely suppressed. There was a problem that it was not possible.

To prevent this, the transistor T
It is sufficient to increase the voltage value of the voltage source of the complementary buffer amplifier AP2 composed of the transistors T12 and T13. However, this requires the transistors T12 and T13 to have a high withstand voltage, which increases the cost. there were.
In general, when the breakdown voltage specification of a transistor is increased, the response performance is reduced, and the output characteristics as a high-pass filter are reduced. As a result, the compensation for suppressing the common mode current is incomplete.

Further, in the conventional device of FIG. 14, the common mode current is suppressed by applying a voltage, and in the conventional device of FIG. 17, the common mode current is suppressed by applying a current. Of course, if these two methods are performed simultaneously, the effect of suppressing the common mode current will increase.
The conventional device shown in FIG. 14 requires a common mode transformer on the output side of the inverter to apply a common mode voltage to the three-phase output voltage of the inverter. Further, the conventional device shown in FIG. 17 requires a common mode transformer on the input side of the inverter to detect the common mode current. Therefore, it is necessary to connect a transformer to each of the input side and the output side of the inverter as a device.
There was a problem that cost, weight, and volume increased.

In the conventional device shown in FIG. 18, the capacitance values of the capacitors C20 and C21 must be the same as the capacitance values of the floating capacitors C18 and C19. Since the length of the output cable 4 changes when the three-phase motor 5 is replaced with another motor, the capacitance values of the capacitors C20 and C21 must be adjusted each time.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems. Even if the power supply voltage of the complementary buffer amplifier is lower, the high-frequency component of the common mode voltage can be reliably suppressed. It is an object of the present invention to obtain a common-mode noise suppression device that becomes:

It is another object of the present invention to further enhance the effect of suppressing the high frequency component. It is another object of the present invention to improve the degree of freedom of the installation positions of the common mode voltage compensating means and the common mode current compensating means and to simplify the configuration when both are provided. It is another object of the present invention to simplify the configuration of the common mode current compensating means.

[0017]

A common mode noise suppressing device according to the present invention comprises a common mode voltage detecting means for detecting a common mode voltage generated in an AC circuit connecting an AC power supply and a load, A common mode transformer comprising a first winding group inserted in series in a phase and a second winding magnetically coupled to the first winding group, and a common mode from the common mode voltage detecting means. A low-pass filter that operates by inputting a voltage via a first buffer; and a second buffer that operates by inputting an output of the low-pass filter; the first buffer and the second buffer Is applied to the second winding to suppress the high frequency component of the common mode voltage in the AC circuit.

Further, in the common mode noise suppressing apparatus according to the present invention, the AC power from the AC power supply is converted into DC power by the first converter, and the DC power from the first converter is converted into the second power. Means for suppressing common mode noise generated in a circuit which converts the power into AC power and supplies the load to a load, and detects a common mode voltage generated in an AC circuit connecting the second conversion means and the load. A common mode voltage detecting means, a first winding group inserted in series in both poles of a DC power path connecting the first converting means and the second converting means, and a magnetic field generated by these first winding groups. A common mode transformer including the coupled second winding, a low-pass filter that operates by inputting a common mode voltage from the common mode voltage detecting means through a first buffer means, and the low-pass filter A second buffer unit that operates by inputting an output of the filter, and by applying an output difference between the first buffer unit and the second buffer unit to the second winding, The high frequency component of the common mode voltage in the AC circuit is suppressed.

Further, the common mode noise suppression device according to the present invention converts AC power from an AC power supply into DC power by a first converter, and converts DC power from the first converter into a second converter. Means for suppressing common mode noise generated in a circuit that is converted into AC power by a means and supplied to a load, and is inserted in series with each phase of an AC circuit connecting the second conversion means and the load. A first winding group, a second winding through which a compensating common mode current flows, a common mode current magnetically coupled to the first winding group and the second winding and generated in the AC electric circuit, and the compensation A common mode transformer comprising a third winding for detecting a difference from the common mode current,
Current amplification means for amplifying the current of the third winding; and coupling means for connecting one end of the second winding to a ground point, wherein the output of the current amplification means is used as the compensation common mode current. By supplying from the ground point through the coupling means, the second winding, and the current amplifying means to the DC circuit connecting the first conversion means and the second conversion means, a common mode in the DC circuit is provided. The current is suppressed.

Further, in the common mode noise suppressing device according to the present invention, the AC power from the AC power supply is converted into DC power by the first conversion means, and the DC power from the first conversion means is converted into the second conversion power. Means for suppressing common mode noise generated in a circuit which is converted into AC power by a means and supplied to a load, and is connected in series to both poles of a DC power line connecting the first converter and the second converter. A common mode transformer comprising an inserted first winding group and a second winding which is magnetically coupled to the first winding group and detects a common mode current generated in the DC power path; Current amplifying means for amplifying the current of the winding, and coupling means for connecting one end of the current amplifying means to a ground point. The output of the current amplifying means is supplied from the ground point to the coupling means and the current amplifying means. Means By supplying to the position of the load side of the first winding insertion position of the DC path Te, in which so as to suppress the common mode current in the DC path.

Further, in the common mode noise suppressing device according to the present invention, the AC power from the AC power supply is converted into DC power by the first conversion means, and the DC power from the first conversion means is converted into the second conversion power. Means for suppressing common mode noise generated in a circuit which converts the power into AC power and supplies the load to a load, and detects a common mode voltage generated in an AC circuit connecting the second conversion means and the load. A common mode voltage detecting means, a first winding group including a first winding group inserted in series with each phase of the AC electric circuit, and a second winding magnetically coupled to the first winding group; Common mode transformer,
A low-pass filter which operates by inputting a common mode voltage from the common mode voltage detection means via a first buffer means, and a second buffer means which operates by inputting an output of the low-pass filter; The output difference between the first buffer means and the second buffer means is determined by the second
A common mode voltage compensating means for suppressing the high frequency component of the common mode voltage in the AC circuit by applying the voltage to the windings, and a third winding group inserted in series with each phase of the AC circuit and a compensation common A difference between a common mode current generated in the AC circuit and a compensation common mode current, which is magnetically coupled to the fourth winding for flowing a mode current, the third winding group, and the fourth winding, is detected. A second common mode transformer including a fifth winding, current amplifying means for amplifying the current of the fifth winding, and coupling means for connecting one end of the fourth winding to a ground point. Connecting the first conversion means and the second conversion means from the ground via the coupling means, the fourth winding and the current amplification means, using the output of the current amplification means as the compensation common mode current. Just A common mode current compensating means for suppressing a common mode current in the direct current circuit by supplying the common mode transformer to the electric circuit, wherein the first and second common mode transformers are integrated to share a magnetic circuit of both. It is.

Further, in the common mode noise suppressing apparatus according to the present invention, the AC power from the AC power supply is converted into DC power by the first converter, and the DC power from the first converter is converted into the DC power by the second converter. Means for suppressing common mode noise generated in a circuit which converts the power into AC power and supplies the load to a load, and detects a common mode voltage generated in an AC circuit connecting the second conversion means and the load. A common mode voltage detecting means, a first winding group inserted in series in both poles of a DC power path connecting the first converting means and the second converting means, and a magnetic field generated by these first winding groups. A first common mode transformer including a coupled second winding, a low-pass filter that operates by inputting a common mode voltage from the common mode voltage detection means via a first buffer means, and A second buffer unit that operates by inputting an output of the pass filter, and applies an output difference between the first buffer unit and the second buffer unit to the second winding, thereby providing the DC power supply. A common mode voltage compensator for suppressing a high frequency component of the common mode voltage in the AC circuit, a third winding group inserted in series with both poles of the DC circuit, and magnetically coupled to the third winding group A second common mode transformer comprising a fourth winding for detecting a common mode current generated in the DC circuit, a current amplifying means for amplifying the current of the fourth winding, and one end of the current amplifying means And a coupling means for connecting the first and third DC power paths from the ground point through the coupling means and the current amplification means. A common mode current compensating means for suppressing a common mode current in the DC power supply by supplying the common mode current to the load side from the winding insertion position. It is an integrated type that shares

In the common mode noise suppression device according to the present invention, the coupling means is a capacitor that cuts off the low frequency range and conducts the high frequency range, thereby suppressing the high frequency component of the common mode current in the DC circuit. It is something to do.

Further, in the common mode noise suppressing device according to the present invention, the AC power from the AC power supply is converted into DC power by the first conversion means, and the DC power from the first conversion means is converted into the second conversion power. Means for suppressing common mode noise generated in a circuit which is converted into AC power by a means and supplied to a load, wherein the first and second conversion means are connected to each other between both poles of a DC power path. It is provided with first and second capacitors connected in series, and by connecting a connection point of the two capacitors and a ground point, thereby suppressing a high frequency component of a common mode current in the DC power circuit. is there.

In the common mode noise suppression device according to the present invention, the low-pass filter is a secondary or higher order filter.

Further, in the common mode noise suppression device according to the present invention, the buffer means is constituted by a complementary buffer amplifier, and the DC power is supplied from a DC power line.

[0027]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows a common mode voltage compensating circuit as a common mode voltage compensating means of the present invention, in which a portion corresponding to 30 in FIG. 14 of the conventional example is newly drawn according to the present invention. Except for the portion shown in FIG. 1, the description is omitted because it is the same as the conventional example. 13 is a low-pass filter. The transistors T1 and T2 constitute a complementary buffer amplifier AP1 as first buffer means having a high input impedance and a low output impedance.
A function of preventing mutual effects between the common mode voltage detecting circuit 15 as the common mode voltage detecting means composed of 4 to C7, the low-pass filter 13, and the common mode transformer CT1 is provided. In the common mode voltage compensating circuit, the potential reference point is the neutral point MP (12) of the DC voltage of the voltage type inverter 2. The neutral point MP is obtained by dividing the voltage Vd into two by capacitors C2 and C3 connected to the positive terminal P and the negative terminal N and having the same capacitance value. The first complementary buffer amplifier AP1 is connected to a voltage source of ± Vs based on the potential of the neutral point MP. The two voltage sources are DC / DC as step-down means.
It is obtained by DC converters 10,11. The output of the first complementary buffer amplifier AP1 is connected to a winding W4 as a second winding of the common mode transformer CT1 and a low-pass filter 13. Transistors T3, T4
The function of preventing the mutual influence between the low-pass filter 13 and the winding W4 is provided by the complementary buffer amplifier AP2 as the second buffer means constituted by.

Next, the operation will be described with reference to FIG.
The common mode voltage detection circuit 15 is connected to the inverter circuit 8
And a three-phase motor 5 to detect a common mode voltage generated in an AC circuit connecting the three-phase motor 5 and the three-phase motor 5. When the potential at the neutral point MP is used as a reference, the common mode voltage v0 of the voltage-type inverter 2 is expressed as v0 = (vU + vV + vW) / 3 using output voltages vU, vV, and vW. In FIG. 1, the input voltage v1 of the first complementary buffer amplifier AP1 is proportional to the common mode voltage v0, and is obtained by voltage division by capacitors C4, C5, C6 and C7. At this time, the voltage v1 is as follows: v1 = Cx / (Cx + C7) * (vU + vV + vW) = k * (vU + vV + vW) / 3 = k * v0 (2) where C4 = C5 = C6 = Cx, k = 3 * Cx / ( Cx + C7) (3)

The voltage v5 applied to the winding W4 is:
The output of the first complementary buffer amplifier AP1 is v2,
Assuming that the input and output of the second complementary buffer amplifier AP2 are v3 and v4, respectively, v5 = v2-v4 ≒ v2-v3 (4) Here, the voltage v3 is obtained by multiplying the voltage v2 by the transfer function of the low-pass filter 13. Because of the waveform, the voltage of v2−v3, that is, the voltage of v5 is a waveform obtained by multiplying the voltage v2 by the transfer function of the high-pass filter. That is, v5 = f * v2 (f: transfer function as a high-pass filter)

This waveform is amplified by the ratio of the winding N1 of W1, W2, W3, which is the first winding of each phase of the common mode transformer CT1, to the winding N2 of the second winding W4, and the voltage v
6, but by setting N1 / N2 = 1 / k, v6 = v5 / k (5) From v2 ≒ v1 = k * v0, v6 ≒ f * v0 (6) That is, the voltage v6 has a characteristic as if the voltage v0 was passed through a high-pass filter. The voltage v6 is applied as a common mode voltage to each of the output voltages vU, vV, vW of the voltage type inverter 2 by the common mode transformer CT1. Accordingly, for example, a material such as a high-frequency ferrite core is used for the common mode transformer CT1 as in the related art. Here, for simplicity of description, it is assumed that the voltages v0, v6, and v7 are measured as shown in FIG. 1 by the common mode voltage measuring devices M1 and M2 that do not actually exist.

FIG. 2 explains the basic operation of the common mode voltage compensation circuit. In the figure, with the horizontal axis as time, (a) shows the common mode voltage v0 in the three-phase motor 5 generated by the inverter circuit 8, and (b) shows the common mode voltage v0 in FIG.
Common mode voltage v1 and low-pass filter 1
3, the output voltage v3, (c) is the voltage v5, and (d) is the common mode voltage v0 before compensation and v7 after compensation. The waveforms for three patterns of the common mode voltage v0 are shown. Since the voltage drop in the first and second complementary buffer amplifiers AP1 and AP2 is small, v
1 ≒ v2, v3 ≒ v4. FIG. 2C shows that the voltage v5 has a characteristic that passes through a high-pass filter as compared with the voltage v1. By adding the compensation common mode voltage v6 to the originally generated common mode voltage v0, the voltage gradient of the common mode voltage v7 generated by the inverter operation becomes as shown in FIG. Compared to the mode voltage v0, it is much lower. That is, the high-frequency component of the common mode voltage is largely suppressed. Further, the common mode voltage compensation operation in the present invention can correspond to various voltage steps as shown in FIG.

For comparison with the conventional example of FIG. 14, FIG.
FIG. 3 shows a common mode voltage compensation operation according to the present invention under the same conditions as the circuit described in FIG. (A) is the common mode voltage v0 in the three-phase motor 5 generated by the inverter circuit 8, (b) is the voltage v2 and v4 in FIG. 1, (c) is the voltage v6, and (d) is the uncompensated common mode voltage. v0 and the compensated common mode voltage v7. In the present invention, since the common mode voltage is compensated using the low-pass filter 13, the voltage is not limited as shown in FIG.

FIG. 4 shows the difference between the output voltage characteristics when the conventional high-pass filter 20 is used and the output voltage characteristics when the low-pass filter 13 according to the present invention is used.
The explanation is attempted with reference to FIG. First, FIG. 4 explains the operation of the common mode voltage compensator according to the configuration of the present invention. In FIG. 4, (a) shows the common mode voltage v0,
(B) is the voltage v4 in the circuit diagram of FIG. 1, and (c) is the voltage v5, which is defined by (v5 = v2−v4). It is assumed that the magnitude of the common mode voltage v0 shown in (a) is a step-like waveform of ± 1 as shown in the figure. At this time, the voltage v4 becomes a waveform obtained by passing the low-pass filter 13 to the waveform of (a) as shown in FIG. Accordingly, the voltage v5 has a waveform like a high-pass filter having a height of 2 as shown in (c), is applied to the winding W4, and functions as a common mode compensation voltage.
At this time, since the voltage output from the complementary buffer amplifier AP2 including the transistors T3 and T4 may have a magnitude of ± 1, the compensation operation can be performed if the magnitude of the power supply voltage Vs in FIG.

Next, the operation of the common mode voltage compensator having the configuration of the conventional example shown in FIG. 5 will be described. In the figure, (a) is the common mode voltage v0, (b) is the voltage v3 in the circuit diagram of FIG. 19, and (c) is the same voltage v4. It is assumed that the magnitude of the common mode voltage v0 shown in (a) is a step-like waveform of plus or minus 1 as in FIG.
At this time, the voltage v3 becomes a waveform obtained by passing the high-pass filter 20 to the waveform of (a) as shown in FIG. Accordingly, the voltage v3 has a waveform having a height of 2. At this time, FIG.
Similarly, if the magnitude of the power supply voltage Vs is 1,
The waveform of the voltage v3 is not transmitted as it is, but becomes a waveform whose peak is cut as shown in FIG. Therefore, as described above, there is a problem that the common mode voltage cannot be completely compensated. In order to completely compensate, it is necessary to double the power supply voltage value for driving the transistors T3 and T4.
Third, the withstand voltage of T4 must be doubled, which increases the cost. Conversely, in the case of the present invention, since the transistors T3 and T4 can be driven at a low voltage, the cost does not increase, and the response characteristics of the complementary buffer amplifier are improved. As a result, the high frequency component of the common mode voltage is reduced. Is achieved more reliably.

As described above, since the slope of the voltage v7 as the common mode voltage generated by the inverter is reduced,
High-frequency leakage current flowing through the floating impedances Z4 and Z5, which have remarkable characteristics as capacitance, can be suppressed. In addition, since the surge voltage generated at the terminal of the three-phase motor 5 is suppressed, the insulation design of the three-phase motor becomes easy. In addition, since the compensation can be performed in accordance with the magnitude of the step of the zero-phase voltage due to any PWM, the effect of suppressing the common mode current can be further increased.

In the above description, the common mode voltage compensating means is inserted in the AC circuit between the voltage type inverter 2 connected to the three-phase system power supply 1 and the three-phase motor 5 as a load. Needless to say, the high frequency component of the common mode voltage generated in the AC circuit may be suppressed by inserting the circuit into a general AC circuit unrelated to the voltage type inverter 2.

Embodiment 2 Next, how the order of the low-pass filter 13 affects the common mode voltage suppression will be described with reference to FIG. When measuring a noise generated by a device such as an inverter toward a system power supply, that is, measuring a so-called noise terminal voltage, a standard impedance is inserted between the device and the system. This is LISN (Line Imp
edanceStabilization Network
rk: pseudo power supply network) and 2 in FIG.
Indicated by 1. The LISN 21 has an impedance Z6 between itself and a ground line. Here, in order to simplify the explanation, the common mode voltage measuring device M3 is
And the voltage type inverter 2.

FIG. 7 schematically shows a common mode equivalent circuit including a common mode voltage compensating circuit in the circuit of FIG. All symbols shown in FIG. 7 are shown in the Laplace area. Here, Zcin represents the parallel-connected impedance of the floating impedances Z1 to Z3 and the impedance Z6 of the LISN 21;
Zcout represents an impedance of the floating impedances Z4 and Z5 connected in parallel. The Laplace transform of the low-pass filter is represented as TLP. The relationship between the common mode voltage v0 of the voltage type inverter and the common mode voltage Vcm measured by the measuring device M3 is expressed as follows. Vcm = (− Zcin / (Zcin + Zcout)) * v0 * TLP (7)

Thus, the common mode voltage Vc on the system side
It can be seen that the effect of suppressing m (the high-frequency component thereof) is directly related to the function TLP of the low-pass filter. Further, the higher the order of the low-pass filter, the higher the effect of suppressing the common mode voltage Vcm. For simple explanation, FIG. 8 shows a compensation effect of the common mode voltage when the order of the low-pass filter is changed. In the figure, (a) is a common mode voltage v0 standardized in unit steps, (b) is a compensation voltage v6 for compensating the common mode voltage, and (c) is v0 * TLP in the above equation (7).
, The compensated common mode voltage v7, (d), indicates the frequency characteristics of the filter. As shown in FIG. 3B, the higher the order of the filter, the smoother the voltage waveform at the point on the time axis 0. Specifically, in the case of the first-order filter, the voltage gradient at the point on the time axis 0 is large, but as the order of the filter increases, the voltage waveform becomes smoother and the voltage gradient decreases. As a result, the voltage rise in the compensated voltage waveform (c) becomes smoother as the order of the filter increases, and as a result, the high-frequency component due to the voltage v7 is suppressed low. When this is confirmed in the frequency domain, as shown in (d), the higher the order of the low-pass filter, the higher the attenuation rate at high frequencies. It is clear that there will be less. Therefore, as the order of the low-pass filter increases, v
The high frequency component of 0 * TCP is reduced, resulting in Zcin and Z
The current flowing through the floating capacitor that forms dominant cout decreases, and noise due to the common mode current can be further suppressed.

Embodiment 3 FIG. 9 is a diagram showing the entire device in the case where the common mode voltage compensation circuit and the common mode current compensation circuit are integrated, and the integrated compensation circuit 3 as the common mode voltage and common mode current compensation means has the three-phase structure. It is connected to an AC circuit between the outputs U, V, W of the voltage type inverter 2 and the three-phase terminals X, Y, Z of the output cable 4. The positive terminal P, the negative terminal N, and the ground line PE are connected to the compensation circuit 3. The basic operation of the common mode voltage compensating circuit is the same as in the first and second embodiments, and the description is omitted. FIG. 10 shows a circuit of the common mode current compensating means in FIG. In the figure, CT2 denotes a second common mode transformer for detecting a common mode current, transistors T5 and T6, and a resistor R1 constitute a current control current source AP3 as current amplification means. The capacitor C8 is coupling means for connecting one end of the winding W5 of the second common mode transformer CT2 to the ground line PE. The common mode transformer CT2 for detecting the common mode current includes an output terminal U of the voltage type inverter 2,
For example, a high-frequency ferrite core is used, and three windings W1, W2, and W3 are wound with the same number of turns N1. The winding W5 for handling low power is also wound with the number of turns N1, and the winding W6 for handling low power is wound with the number of turns N3. The common mode transformer CT2 detects a common mode current Ic1 output to the load side by the voltage type inverter 2. The current Ic1 flows from the three-phase motor 5 to the voltage-type inverter 2 via a ground line PE. The capacitor C8 is connected to decouple the winding W6 of the transformer CT2 and the ground line PE at a low frequency, that is, to cut off the low frequency band and conduct the high frequency band.

The purpose of the common mode current compensation circuit is to control the current Ic2 in the figure as a compensation current (compensation common mode current). By supplying the current Ic2 to the DC circuit connecting the diode bridge circuit 7 and the inverter circuit 8 through the capacitor C8, the common mode current Ic3 flowing through the ground line PE is suppressed, and as a result, the three-phase system power supply The common mode current flowing to the side can be largely suppressed.
To explain the detailed operation, in order to control the compensation current Ic2 equal to Ic1, the common mode transformer CT
2 detects the current Ic4 obtained by amplifying the difference between the currents Ic1 and Ic2 (that is, the current after compensation) using the winding W6 according to the following equation. Ic4 = α * (Ic1-Ic2) (8) α = N1 / N3: turns ratio (9)

The current Ic4 is further amplified and output by the current control current source AP3. The output current Ic3 of the current control current source AP3 changes β by transistors T5 and T6.
The current amplification gain is as follows. Ic5 = (1 + β) * Ic4 (10) As a result, the relationship between the compensation common mode current Ic2 and the common mode current Ic3 is as follows. Ic2 = ((α * β) / (1 + α * β)) * Ic1 (11) Ic3 = (1 / (1 + α * β)) * Ic1 (12) From the above, the larger the turns ratio α, the more the transistor Is larger, the current Ic2 becomes equal to the current Ic1. The above capacitor C
8, the current Ic2 flowing through the DC capacitor C1 becomes the current Icpn flowing through the DC capacitor C1, and does not flow to the system power supply. Can be.

As described above, in the third embodiment, by providing the common mode transformer CT2 with the windings W5 and W6, the position of the AC circuit on the load side with respect to the DC circuit for supplying the compensation common mode current is increased. Despite the configuration, the current equivalent to the compensated current can be detected, so both the common mode transformer for common mode voltage compensation and the common mode transformer for common mode current compensation are inserted into the same AC circuit. can do. That is, the common mode transformer for compensating for the common mode current, which was on the input side of the inverter in the conventional example, can be connected to the AC circuit on the output side of the inverter in the present invention, so that the common mode transformers CT2 and CT2 in FIG. 1 common mode transformer CT1 for common mode voltage compensation
It can be configured as one transformer. FIG. 11 shows a configuration example in which the common mode transformers CT1 and CT2 are integrated. As shown in FIG. 11, the common mode voltage compensating circuit and the common mode transformers CT1 and CT2 in the common mode current compensating circuit are integrated with each other by using two ferrite cores. Winding W5 for low power
And the thickness of the ferrite core 1 relating to W6 can be reduced.

As described above, according to the present invention, the common mode voltage compensating circuit suppresses the current Ic1, and the common mode current compensating circuit further bypasses the remaining Ic1 toward the DC circuit of the voltage type inverter. Therefore, the common mode current flowing through the three-phase system power supply 1 is significantly suppressed, and the generation of noise from the inverter device to the system can be further suppressed.

Further, since the common mode voltage compensating circuit is constituted by using a low-pass filter, it can cope with any step of the common mode voltage due to any pulse width modulation, so that generation of noise can be suppressed more reliably. Becomes

Further, since the common mode transformer required for the common mode voltage compensating circuit and the common mode current compensating circuit is integrated, the size and weight of the device and the cost can be reduced.

In the above description, the compensation common mode current I
Although a capacitor C8 that cuts off low-frequency components and conducts high-frequency components is adopted as coupling means that constitutes the current path of c2, high-frequency components of the common mode current are suppressed. The frequency range to be suppressed in the common mode current may be expanded by adopting the coupling means having the following.

Embodiment 4 FIG. 12 shows another embodiment in which the common mode voltage compensation circuit and the common mode current compensation circuit are integrated. In the figure, reference numeral 25 denotes a compensation circuit in which a common mode voltage compensation circuit as a common mode voltage common mode current compensation means and a common mode current compensation circuit are integrated. In the common mode voltage compensating circuit, the common mode voltage detecting circuit 15 is provided on the AC circuit which is the output cable 4 as in the previous embodiment, but the common mode transformer CT3 includes the diode bridge circuit 7 and the inverter circuit 8. It is configured to be inserted into a DC path to be connected, and to supply the compensation voltage v5 supplied to the winding W4 to this DC path via the windings W2 and W3. The basic operation is the same as that of the above embodiment, and further description is omitted.

On the other hand, in the common mode current compensating circuit, the common mode transformer CT4 is provided on the DC circuit, and the windings W2 and W3 inserted in series in both poles of the DC circuit and the two windings W2 and W3 are magnetically coupled. Winding W coupled to
5, and amplifies the current detected and supplies its output to a position on the load side of the common mode transformer CT4 on the DC power path. That is, except that the common mode transformer is provided on the DC power path on the load side of the diode bridge circuit 7, the common mode transformer is provided on the conventional AC line on the power supply side of the diode bridge circuit 7, as shown in FIG. There is basically no difference from the common mode current compensation circuit. Of course, the configuration of the common mode current compensation circuit described with reference to FIG. 10 may be employed.

As described above, by connecting the compensation circuit 25 to the DC circuit of the voltage type inverter 2,
Not only the leakage current flowing through the floating impedances Z4 and Z5 can be suppressed, but also the leakage current flowing through the floating impedance Z3 existing between the semiconductor switch and the heat sink 9 can be suppressed. Noise generation can be further suppressed.

The common mode voltage compensating circuit has three
Suppresses the common mode current Ic1 flowing through the phase motor 5,
The common mode current compensating circuit further includes the remaining Ic
1 is bypassed to the DC circuit of the voltage type inverter 2, the common mode current flowing through the three-phase system power supply 1 is greatly suppressed, and the generation of noise from the inverter device to the system side can be further suppressed. .

The common mode voltage compensating circuit and the common mode transformer required for the common mode current compensating circuit are integrated, and the integrated common mode voltage compensating circuit and common mode current compensating circuit are shown in FIG. , The number of windings in the common mode transformer can be reduced by one in each compensation circuit, compared with the case of connecting to a three-phase AC circuit. Small size, light weight and low cost can be realized.

Further, since the common mode voltage compensating circuit is constituted by using a low-pass filter, it can cope with any step of the common mode voltage due to any pulse width modulation, and the generation of noise can be suppressed more reliably. Becomes

Embodiment 5 FIG. FIG. 13 is a circuit configuration diagram showing a common mode noise suppression device according to Embodiment 5 of the present invention. Also in this case, the common mode voltage compensating circuit and the common mode current compensating circuit are provided side by side to effectively suppress the common mode current. However, the former common mode voltage compensating circuit is the same as that described with reference to FIG. 1 of the first embodiment, and a description thereof will not be repeated. The latter common mode current compensation circuit is significantly different from the above embodiment. That is, as shown in FIG. 13, a capacitor C3 connected in series between the P and N poles of the DC circuit of the voltage type inverter 2
0 and C31, and both capacitors C30, C31
Is connected to the ground line PE.

The common mode current compensating circuit according to the fifth embodiment does not actively send a compensating current to a line to compensate, but in the example of FIG. Z2, Z
3, the current flowing through Z4 and Z5
30 and return to the above-mentioned DC circuit in the form of sucking up through C31. In other words, the common mode current generated on the load side is confined in an annular flow path formed by each electric circuit and the ground line PE, thereby suppressing the common mode current on the power supply side.

Usually, the common mode noise is measured by inserting the LISN 21 on the power supply side of the converter as illustrated in FIG. Therefore, if attention is paid to this point, the common mode current compensating circuit shown in FIG. 13 also exhibits a sufficient function as a common mode noise suppressing device, does not require a common mode transformer, has a very simple configuration, and has a low cost. There are advantages.

Although the first to fifth embodiments have described examples of three-phase inverters, it is needless to say that the present invention can be applied to single-phase and multi-phase inverters.

Further, in the first to fifth embodiments, the case where the output of the inverter is two levels is described. However, it is needless to say that the present invention can be applied to an inverter having three or more levels of voltage output.

[0059]

As described above, the common mode noise suppression device according to the present invention comprises a common mode voltage detecting means for detecting a common mode voltage generated in an AC circuit connecting an AC power supply and a load, A common mode transformer including a first winding group inserted in series with each phase and a second winding magnetically coupled to the first winding group; A low-pass filter that operates by inputting a mode voltage through a first buffer; and a second buffer that operates by inputting an output of the low-pass filter; the first buffer and the second buffer By applying the output difference from the means to the second winding, the high frequency component of the common mode voltage in the AC circuit is suppressed.
An accurate compensation voltage for suppressing a high-frequency component can be formed without particularly increasing the power supply voltage of the buffer means, and the high-frequency component of the common mode voltage in the AC circuit can be surely suppressed.

Further, in the common mode noise suppressing apparatus according to the present invention, the AC power from the AC power supply is converted into DC power by the first conversion means, and the DC power from the first conversion means is converted into the second conversion power. Means for suppressing common mode noise generated in a circuit which converts the power into AC power and supplies the load to a load, and detects a common mode voltage generated in an AC circuit connecting the second conversion means and the load. A common mode voltage detecting means, a first winding group inserted in series in both poles of a DC power path connecting the first converting means and the second converting means, and a magnetic field generated by these first winding groups. A common mode transformer including the coupled second winding, a low-pass filter that operates by inputting a common mode voltage from the common mode voltage detecting means through a first buffer means, and the low-pass filter A second buffer unit that operates by inputting an output of the filter, and by applying an output difference between the first buffer unit and the second buffer unit to the second winding, Since the high-frequency component of the common mode voltage in the AC circuit is suppressed, an accurate compensation voltage for suppressing the high-frequency component can be formed without particularly increasing the power supply voltage of the buffer means. The high-frequency component of the common mode voltage in the AC circuit can be reliably suppressed. In addition, regardless of the number of AC phases of the AC circuit, the common mode transformer can be a small-sized one having only two first windings.

Further, in the common mode noise suppressing device according to the present invention, the AC power from the AC power supply is converted into DC power by the first conversion means, and the DC power from the first conversion means is converted into the second conversion power. Means for suppressing common mode noise generated in a circuit that is converted into AC power by a means and supplied to a load, and is inserted in series with each phase of an AC circuit connecting the second conversion means and the load. A first winding group, a second winding through which a compensating common mode current flows, a common mode current magnetically coupled to the first winding group and the second winding and generated in the AC electric circuit, and the compensation A common mode transformer comprising a third winding for detecting a difference from the common mode current,
Current amplification means for amplifying the current of the third winding; and coupling means for connecting one end of the second winding to a ground point, wherein the output of the current amplification means is used as the compensation common mode current. By supplying from the ground point through the coupling means, the second winding, and the current amplifying means to the DC circuit connecting the first conversion means and the second conversion means, a common mode in the DC circuit is provided. Since the current is suppressed, it is possible to suppress the common mode current by adopting a configuration in which a common mode transformer is inserted into an AC power line that is not to be compensated.

Further, in the common mode noise suppressing device according to the present invention, the AC power from the AC power supply is converted into DC power by the first converter, and the DC power from the first converter is converted into the second power by the second converter. Means for suppressing common mode noise generated in a circuit which is converted into AC power by a means and supplied to a load, and is connected in series to both poles of a DC power line connecting the first converter and the second converter. A common mode transformer comprising an inserted first winding group and a second winding which is magnetically coupled to the first winding group and detects a common mode current generated in the DC power path; Current amplifying means for amplifying the current of the winding, and coupling means for connecting one end of the current amplifying means to a ground point. The output of the current amplifying means is supplied from the ground point to the coupling means and the current amplifying means. Means By supplying the DC circuit to a position closer to the load than the first winding insertion position, the common mode current in the DC circuit is suppressed. The mode transformer can be reduced in size to have only two first windings to suppress the common mode current.

Further, the common mode noise suppressing device according to the present invention converts AC power from an AC power supply into DC power by a first converter, and converts DC power from the first converter into a second converter. Means for suppressing common mode noise generated in a circuit which converts the power into AC power and supplies the load to a load, and detects a common mode voltage generated in an AC circuit connecting the second conversion means and the load. A common mode voltage detecting means, a first winding group including a first winding group inserted in series with each phase of the AC electric circuit, and a second winding magnetically coupled to the first winding group; Common mode transformer,
A low-pass filter which operates by inputting a common mode voltage from the common mode voltage detection means via a first buffer means, and a second buffer means which operates by inputting an output of the low-pass filter; The output difference between the first buffer means and the second buffer means is determined by the second
A common mode voltage compensating means for suppressing the high frequency component of the common mode voltage in the AC circuit by applying the voltage to the windings, and a third winding group inserted in series with each phase of the AC circuit and a compensation common A difference between a common mode current generated in the AC circuit and a compensation common mode current, which is magnetically coupled to the fourth winding for flowing a mode current, the third winding group, and the fourth winding, is detected. A second common mode transformer including a fifth winding, current amplifying means for amplifying the current of the fifth winding, and coupling means for connecting one end of the fourth winding to a ground point. Connecting the first conversion means and the second conversion means from the ground via the coupling means, the fourth winding and the current amplification means, using the output of the current amplification means as the compensation common mode current. Just A common mode current compensating means for suppressing a common mode current in the direct current circuit by supplying to the electric circuit, and the first and second common mode transformers are formed as an integral type sharing a magnetic circuit of both. In addition, both a common mode transformer for common mode voltage compensation and a common mode transformer for common mode current compensation can be inserted into the AC circuit, and the magnetic circuit can be shared to achieve downsizing.

Also, the common mode noise suppression device according to the present invention converts AC power from an AC power supply into DC power by a first converter, and converts DC power from the first converter into a second converter. Means for suppressing common mode noise generated in a circuit which converts the power into AC power and supplies the load to a load, and detects a common mode voltage generated in an AC circuit connecting the second conversion means and the load. A common mode voltage detecting means, a first winding group inserted in series in both poles of a DC power path connecting the first converting means and the second converting means, and a magnetic field generated by these first winding groups. A first common mode transformer including a coupled second winding, a low-pass filter that operates by inputting a common mode voltage from the common mode voltage detection means via a first buffer means, and A second buffer unit that operates by inputting an output of the pass filter, and applies an output difference between the first buffer unit and the second buffer unit to the second winding, thereby providing the DC power supply. A common mode voltage compensator for suppressing a high frequency component of the common mode voltage in the AC circuit, a third winding group inserted in series with both poles of the DC circuit, and magnetically coupled to the third winding group A second common mode transformer comprising a fourth winding for detecting a common mode current generated in the DC circuit, a current amplifying means for amplifying the current of the fourth winding, and one end of the current amplifying means And a coupling means for connecting the first and third DC power paths from the ground point through the coupling means and the current amplification means. A common mode current compensating means for suppressing a common mode current in the DC power supply by supplying the common mode current to the load side from the winding insertion position. The common mode transformer for common mode voltage compensation and common mode current compensation can be inserted into the DC circuit to share the magnetic circuit, and the number of AC phases in the AC circuit can be reduced. Regardless, the first and third windings of the common mode transformer can be both small and small.

Further, in the common mode noise suppressing device according to the present invention, the coupling means is a capacitor that cuts off the low frequency range and conducts the high frequency range, thereby suppressing the high frequency component of the common mode current in the DC circuit. Therefore, the high frequency component of the common mode current can be efficiently compensated.

Further, in the common mode noise suppression device according to the present invention, the AC power from the AC power supply is converted into DC power by the first conversion means, and the DC power from the first conversion means is converted into the second power. Means for suppressing common mode noise generated in a circuit which is converted into AC power by a means and supplied to a load, wherein the first and second conversion means are connected to each other between both poles of a DC power path. Since the first and second capacitors are connected in series, and the connection point of the two capacitors is connected to the ground point, the high-frequency component of the common mode current in the DC circuit is suppressed. It is possible to suppress the high frequency component of the common mode current with a very simple configuration.

Further, in the common mode noise suppressing device according to the present invention, the low-pass filter is a secondary or higher order filter, so that the common mode noise suppressing effect is further improved.

Further, in the common mode noise suppressing apparatus according to the present invention, the buffer means is constituted by a complementary buffer amplifier, and the DC power is supplied from the DC circuit, so that a special power supply for the buffer means is provided. Is unnecessary, and the economic efficiency is improved.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a common mode voltage compensation circuit according to Embodiment 1 of the present invention.

FIG. 2 is a diagram showing operation waveforms for three types of common mode voltages in the circuit of FIG.

FIG. 3 is a waveform diagram showing FIG. 2 converted under the same conditions to facilitate comparison with the conventional case.

FIG. 4 is a diagram illustrating the operation of a low-pass filter.

FIG. 5 is a diagram illustrating the operation of a high-pass filter.

FIG. 6 is a diagram showing a configuration of a common mode voltage compensation circuit according to a second embodiment of the present invention.

FIG. 7 is a diagram illustrating a common mode voltage compensation characteristic of the circuit in FIG. 6 using a low-pass filter.

FIG. 8 is a diagram illustrating common mode voltage compensation characteristics when the order of a low-pass filter is changed in the circuit of FIG. 6;

FIG. 9 is a diagram showing a configuration of a common mode noise suppression device according to Embodiment 3 of the present invention.

10 is a diagram illustrating the common mode current compensation characteristics of the common mode current compensation circuit of FIG.

11 is a diagram showing a configuration of the common mode transformer of FIG.

FIG. 12 is a diagram showing a configuration of a common mode noise suppression device according to Embodiment 4 of the present invention.

FIG. 13 is a diagram showing a configuration of a common mode noise suppression device according to a fifth embodiment of the present invention.

FIG. 14 is a diagram illustrating a configuration of a conventional common mode voltage compensation circuit.

FIG. 15 is a diagram showing waveforms of a phase voltage and a common mode voltage generated by the inverter.

FIG. 16 is a diagram illustrating the principle of generation of a common mode current generated by an inverter.

FIG. 17 is a diagram showing a configuration of a conventional common mode current compensation circuit.

FIG. 18 is a diagram showing a configuration of a conventional common mode current compensation circuit.

19 is a diagram illustrating the common mode voltage compensation characteristics of the circuit of FIG.

20 is a diagram showing operation waveforms for three types of common mode voltages in the circuit of FIG.

[Explanation of symbols]

Reference Signs List 1 3 phase power supply, 2 voltage type inverter, 5 3 phase motor, 7 diode bridge circuit, 8 inverter circuit, 13 low pass filter, 15 common mode voltage detection circuit, CT1 to CT4 common mode transformer, A
P1, AP2 Complementary buffer amplifier, AP3 current control current source, C8, C30, C31 capacitors, PE
Ground wire.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Masahiro Kizen 2-3-2 Marunouchi, Chiyoda-ku, Tokyo Mitsubishi Electric Corporation F-term (reference) 5H007 AA01 AA08 BB06 CA01 CB05 CC09 DC05 HA02 5H740 BA18 BB05 BB09 BB10 BC01 BC02 BC10 MM01 NN02 PP10 5J024 AA01 BA14 CA19 DA01 DA26 EA09

Claims (10)

[Claims] 1. A common mode voltage detecting means for detecting a common mode voltage generated in an AC circuit connecting an AC power supply and a load, and a first mode inserted in series with each phase of the AC circuit.
And a common mode transformer composed of a second winding group and a second winding magnetically coupled to the first winding group. The common mode voltage from the common mode voltage detecting means is supplied to the common buffer via the first buffer means. A low-pass filter that operates by inputting and outputting the output of the low-pass filter; and a second buffer that operates by inputting the output of the low-pass filter. A common mode noise suppression device configured to suppress a high frequency component of a common mode voltage in the AC electric circuit by applying a voltage to a winding. 2. An AC power from an AC power supply is converted into DC power by a first converter, and a DC power from the first converter is converted into an AC power by a second converter and supplied to a load. A common mode voltage detecting means for detecting a common mode voltage generated in an AC circuit connecting the second converting means and a load, the first converting means comprising: A first winding group inserted in series into both poles of a DC circuit connecting the means and the second conversion means, and a second winding magnetically coupled to the first winding group. A common-mode transformer, a low-pass filter which operates by inputting a common-mode voltage from the common-mode voltage detection means via the first buffer means, and a second buffer circuit which operates by inputting the output of the low-pass filter And applying an output difference between the first buffer means and the second buffer means to the second winding so as to suppress a high-frequency component of a common mode voltage in the DC circuit and the AC circuit. Common mode noise suppression device. 3. An AC power from an AC power supply is converted into DC power by a first converter, and a DC power from the first converter is converted into an AC power by a second converter and supplied to a load. A first winding group inserted in series into each phase of an AC circuit connecting the second conversion means and a load, and a compensation common mode current. And a third coil for magnetically coupling the second winding, the first winding group, and the second winding, and detecting a difference between a common mode current generated in the AC electric circuit and the compensation common mode current. Common mode transformer consisting of
Current amplifying means for amplifying the current of the winding of
And a coupling means for connecting one end of the winding of the above-mentioned winding to a ground point, and using the output of the current amplifying means as the compensation common mode current from the ground point to the coupling means, the second winding and the current amplifying means. By supplying to the DC power path connecting the first conversion means and the second conversion means via
A common mode noise suppression device configured to suppress a common mode current in the DC circuit. 4. An AC power from an AC power supply is converted into DC power by a first converter, and a DC power from the first converter is converted into an AC power by a second converter and supplied to a load. And a first winding group inserted in series in both poles of a DC circuit connecting the first converter and the second converter. A second winding for magnetically coupling to the first winding group and detecting a common mode current generated in the DC power path; and a current amplifying means for amplifying the current of the second winding. And coupling means for connecting one end of the current amplifying means to a ground point. The output of the current amplifying means is supplied from the ground point via the coupling means and the current amplifying means to the first of the DC circuit. Load from winding insertion position By supplying the position, common-mode noise reduction device so as to suppress the common mode current in the DC path. 5. An AC power from an AC power supply is converted into DC power by a first converter, and a DC power from the first converter is converted into an AC power by a second converter and supplied to a load. A common mode voltage detecting means for detecting a common mode voltage generated in an AC circuit connecting the second conversion means and a load; and A first common mode transformer comprising a first winding group inserted in series in a phase and a second winding magnetically coupled to the first winding group; A low-pass filter which operates by inputting the common mode voltage of the first buffer means via a first buffer means, and a second buffer means which operates by inputting the output of the low-pass filter. A common mode voltage compensating means for suppressing a high frequency component of a common mode voltage in the AC circuit by applying an output difference from the buffer means to the second winding, and being inserted in series with each phase of the AC circuit. The third winding group, the fourth winding through which the compensation common mode current flows, the common mode current magnetically coupled to the third winding group and the fourth winding, and generated in the AC circuit. A second common mode transformer comprising a fifth winding for detecting a difference from the compensation common mode current, a current amplifying means for amplifying the current of the fifth winding, and one end of the fourth winding. And a coupling means for connecting the output of the current amplifying means as the compensation common mode current from the ground point via the coupling means, a fourth winding and a current amplifying means. Strange Supply to the direct current path connecting the conversion means and the second conversion means,
A common mode noise suppression device comprising: a common mode current compensator for suppressing a common mode current in the direct current circuit; and wherein the first and second common mode transformers are integrated to share both magnetic circuits. 6. An AC power from an AC power supply is converted into DC power by a first converter, and a DC power from the first converter is converted into an AC power by a second converter and supplied to a load. A common mode voltage detecting means for detecting a common mode voltage generated in an AC circuit connecting the second converting means and a load, the first converting means comprising: A first winding group inserted in series into both poles of a DC circuit connecting the means and the second conversion means, and a second winding magnetically coupled to the first winding group. A first common mode transformer, a low-pass filter which operates by inputting a common mode voltage from the common mode voltage detection means via a first buffer means, and a second which operates by inputting an output of the low-pass filter.
By applying an output difference between the first buffer means and the second buffer means to the second winding, a high-frequency component of a common mode voltage in the DC circuit and the AC circuit is suppressed. A common mode voltage compensating means, a third winding group inserted in series with both poles of the DC circuit, and a common mode current magnetically coupled to the third winding group and generated in the DC circuit. A second common mode transformer comprising a fourth winding to be connected, a current amplifying means for amplifying the current of the fourth winding, and a coupling means for connecting one end of the current amplifying means to a ground point. The output of the current amplifying means is supplied from the ground point through the coupling means and the current amplifying means to a position on the load side of the DC power path from the first and third winding insertion positions. And a common mode current compensator for suppressing a common mode current in the direct current circuit, wherein the first and second common mode transformers are integrated into a common mode noise suppressing device that shares a magnetic circuit of both. . 7. A high-frequency component of a common mode current in a DC circuit is suppressed by using a coupling means as a capacitor that blocks a low frequency band and conducts a high frequency band. 7. The common mode noise suppression device according to any one of claims 6 to 6. 8. An AC power from an AC power supply is converted into DC power by a first converter, and a DC power from the first converter is converted into an AC power by a second converter and supplied to a load. The first and second converters are connected in series between both poles of a DC circuit connecting the first converter and the second converter. A common mode noise suppression device comprising: a capacitor; and connecting a connection point of the two capacitors and a ground point to suppress a high frequency component of a common mode current in the DC circuit. 9. The method according to claim 1, wherein the low-pass filter is a second-order or higher-order filter.
The common mode noise suppression device according to any one of the above. 10. The common mode according to claim 2, wherein the buffer means is constituted by a complementary buffer amplifier, and its DC power is supplied from a DC circuit. Noise suppression device.