JP2008283755A - Surge suppression circuit and inverter driving motor system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To get surge suppression effect to zero-phase components while reducing a leakage current. <P>SOLUTION: A surge suppressing circuit 16 is provided with resistors RN1-RN3 and capacitors CN1-CN3, and one end of a series circuit consisting of these resistors RN1-RN3 and capacitors CN1-CN3 is connected to each phase of a motor receiving end T2, and also the other end of this series circuit is connected to the neutral point V<SB>M</SB>of DC voltage of an inverter 13. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a surge suppression circuit and an inverter drive motor system, and particularly suitable for a surge voltage suppression method in an inverter that controls an output voltage waveform with a switching element and supplies power to a motor via a cable. It is.

In an inverter drive motor system, an output voltage waveform is controlled by a switching element provided in the inverter, and electric power is supplied to the motor via a cable.
FIG. 4 is a diagram showing a schematic configuration of a conventional inverter drive motor system.
In FIG. 4, the input side of the inverter 13 is connected to a commercial power source via the converter 12 and the transformer 11 in sequence, and the output side of the inverter 13 is connected to the motor 15 via the cable 14.

  Here, the converter 12 is provided with switching elements S11 to S22 and diodes D11 to S28. In the switching elements S11 to S22, the diodes D11 to S22 are connected in antiparallel, the switching elements S11 to S14 are connected in series, the switching elements S15 to S18 are connected in series, and the switching elements S19 to S22 are They are connected in series with each other.

The switching elements S11 to S14 connected in series, the switching elements S15 to S18 connected in series, and the switching elements S19 to S22 connected in series are connected in parallel to each other.
The diodes D23 and D24 are connected in series with each other, and the diodes D23 and D24 connected in series are connected in reverse parallel to the switching elements S12 and S13 connected in series. The diodes D25 and D26 are connected in series with each other, and the diodes D25 and D26 connected in series are connected in reverse parallel to the switching elements S16 and S17 connected in series. Furthermore, the diodes D27 and D28 are connected in series with each other, and the diodes D27 and D28 connected in series are connected in reverse parallel to the switching elements S20 and S21 connected in series.

The connection points of the switching elements S12 and S13, the connection points of the switching elements S16 and S17, and the connection points of the switching elements S20 and S21 are connected to each phase of the commercial power supply via the transformer 11, respectively.
That is, in converter 12, switching elements S11-S14 and diodes D11-D14 can handle one phase, and switching elements S15-S18 and diodes D15-D18 can handle another phase. The switching elements S19 to S22 and the diodes D19 to D22 can further handle another one phase.

The inverter 13 is provided with switching elements S51 to S62 and diodes D51 to D68. In the switching elements S51 to S62, the diodes D51 to S62 are connected in antiparallel, the switching elements S51 to S54 are connected in series, the switching elements S55 to S58 are connected in series, and the switching elements S59 to S62 are They are connected in series with each other.
The switching elements S51 to S54 connected in series, the switching elements S55 to S58 connected in series, and the switching elements S59 to S62 connected in series are connected in parallel to each other.

  The diodes D63 and D64 are connected in series to each other, and the diodes D63 and D64 connected in series are connected in reverse parallel to the switching elements S62 and S63 connected in series. The diodes D65 and D66 are connected in series with each other, and the diodes D65 and D66 connected in series are connected in reverse parallel to the switching elements S56 and S57 connected in series. Furthermore, the diodes D67 and D68 are connected in series with each other, and the diodes D67 and D68 connected in series are connected in reverse parallel to the switching elements S60 and S61 connected in series.

The connection points of the switching elements S52 and S53, the connection points of the switching elements S56 and S57, and the connection points of the switching elements S60 and S61 are connected to the respective phases of the motor 15 via the cable 14.
That is, in the inverter 13, the switching elements S51 to S54 and the diodes D51 to D54 can take charge of one phase, and the switching elements S55 to S58 and the diodes D55 to D58 can take charge of the other phase. The switching elements S59 to S62 and the diodes D59 to D62 can further handle another one phase.

The DC capacitors C1 and C2 are connected in series, and both ends of the DC capacitors C1 and C2 connected in series are respectively connected to both ends of the switching elements S15 to S18 connected in series, and the switching elements connected in series. Connected to both ends of S55 to S58, respectively.
Further, the connection point of the diodes D23 and D24 connected in series, the connection point of the diodes D25 and D26 connected in series, and the connection point of the diodes D27 and D28 connected in series are connected to the connection point of the DC capacitors C1 and C2. In addition, the connection point of the diodes D63 and D64 connected in series, the connection point of the diodes D65 and D66 connected in series, and the connection point of the diodes D67 and D68 connected in series are connected to the connection point of the DC capacitors C1 and C2. Yes.

  For example, one phase of the inverter 13 is described. For example, a positive DC voltage can be output by turning on the switching elements S51 and S52, and a zero voltage can be obtained by turning on the switching elements S52 and S53. A negative DC voltage can be output by turning on the switching elements S53 and S54, and it can be operated as a three-level inverter that outputs a three-level voltage for each phase.

In the three-level inverter, the DC voltage = 2Vd rectified by the converter 12 is divided into Vd by the DC capacitors C1 and C2 having the same capacity.
Here, in the inverter drive motor system, the switching elements S11 to S22 of the inverter 13 are turned on / off at a frequency of several kHz to several tens of kHz, and the voltage at the inverter output terminal T1 is a pulse voltage with a steep rise and fall. Become. Further, the impedance of the motor 15 is extremely large compared to the impedance of the cable 14.

For this reason, in the inverter drive motor system, when electric power is supplied from the inverter 13 to the motor 15, the voltage is reflected at the motor power receiving end T2, and a voltage about twice that of the inverter output end T1 is applied as a surge voltage.
This surge voltage causes insulation breakdown between the lines of the motor 15 and between the ground and the life of the insulating part of the motor winding due to partial discharge. As a method of suppressing such a surge voltage, there is a method of connecting a surge suppression circuit to the motor receiving end T2 (Patent Document 1).

FIG. 5 is a diagram showing a schematic configuration of an inverter drive motor system to which a conventional surge suppression circuit is applied.
In FIG. 5, the surge suppression circuit 16 is provided with resistors RN1 to RN3 and capacitors CN1 to CN3. The resistor RN1 and the capacitor CN1 are connected in series, the resistor RN2 and the capacitor CN2 are connected in series, and the resistor RN3 and the capacitor CN3 are connected in series. One end of a series circuit composed of these resistors RN1 to RN3 and capacitors CN1 to CN3 is connected to each phase of the motor receiving end T2, and the other ends of these series circuits are connected in common.

Then, by setting the values of the resistors RN1 to RN3 of the surge suppression circuit 16 to the same value as the impedance of the cable 14, reflection due to impedance mismatch at the motor receiving end T2 is reduced, and the surge voltage is suppressed. Can do.
Here, when the three-phase voltage is expressed with respect to the predetermined reference potential, the first component obtained by multiplying the value obtained by adding the instantaneous value of the three-phase voltage by a coefficient of 1/3 and the instantaneous value of the three-phase voltage are calculated. The three-phase voltage can be separated into a second component obtained by subtracting one component.

This first component is called a zero-phase component, and in the three-phase three-wire system, it is a voltage component that causes a leakage current that flows through the stray capacitance of the circuit. The three-phase voltage of the second component is called a symmetric component, and becomes zero when the instantaneous values are added.
For example, even if a three-phase surge voltage with respect to the ground is added, it does not become zero, so the surge voltage includes a zero-phase component.

Further, Patent Document 2 does not increase the current of the switching element due to an AC short circuit between lines, does not cause resonance between lines and resonance at a neutral point, reduces high frequency noise, and leaks of electric equipment such as a motor. To configure a filter that reduces current, connect one line of a series connection of a capacitor and a resistor to each line between the common mode choke coil and the electrical equipment, and connect the other end of the series connection together in common. A method of connecting the other end of the serial connection body to a virtual ground potential portion having a potential equivalent to ground with respect to a frequency component higher than that of the AC power supply is disclosed.
JP-A-11-262245 JP 2001-69762 A

However, in the surge suppression circuit 16 of FIG. 5, since the instantaneous value of the three-phase current flowing therethrough is zero, there is no surge suppression in the zero-phase component of the surge voltage, and only the symmetrical component of the surge voltage There was a problem that it could not be suppressed.
Here, in order to obtain the surge suppression effect for the zero-phase component, a method of grounding the other end of the series circuit including resistors RN1 to RN3 and capacitors CN1 to CN3 as shown in FIG. .

However, the method of FIG. 6 has a problem in that all the leakage current I _{reakage that} has passed through the surge suppression circuit 16 flows to the ground, and the leakage current I _reakage increases.
Moreover, in order to connect the other end of the series connection body connected in common, it is necessary to provide a virtual ground potential portion having a potential equivalent to the ground with respect to a frequency component higher than the AC power supply, and there is no virtual ground potential portion. In some cases, it was not applicable.
Accordingly, an object of the present invention is to provide a surge suppression circuit and an inverter drive motor system capable of obtaining a surge suppression effect against a zero-phase component while reducing leakage current.

In order to solve the above-described problem, according to the surge suppression circuit according to claim 1, in the surge suppression circuit connected to the power receiving end of the motor supplied with power from the multi-level inverter via a cable, the surge suppression circuit The circuit includes a series circuit in which a first resistor having a value set so that reflection due to impedance mismatch at the power receiving end of the motor is reduced and a first capacitor are connected in series, One end is connected to the power receiving end of the motor, and the other end of the series circuit is connected to a neutral point of the DC voltage of the multilevel inverter.
The surge suppression circuit according to claim 2 further includes a second resistor or a second capacitor connected in series to the series circuit and having a value set so as to obtain impedance matching for the zero-phase component. It is characterized by providing.

According to the inverter drive motor system of claim 3, a multi-level inverter that supplies electric power to the motor, a cable that connects the motor and the multi-level inverter, and a surge that is connected to the power receiving end of the motor A first resistor whose value is set so that reflection due to impedance mismatch at the power receiving end of the motor is reduced, and a first capacitor are connected in series. A series circuit is provided, and one end of the series circuit is connected to a power receiving end of the motor, and the other end of the series circuit is connected to a neutral point of the DC voltage of the multilevel inverter.
According to the inverter drive motor system of claim 4, the second resistor or the second capacitor connected in series to the series circuit and set to have impedance matching for the zero phase component is provided. It is further provided with the feature.

  As described above, according to the present invention, the other end of the series circuit of the surge suppression circuit is connected by connecting the other end of the series circuit provided in the surge suppression circuit to the neutral point of the DC voltage of the multilevel inverter. Is maintained at the same potential as the ground point of the commercial power supply, and the leakage current that has passed through the surge suppression circuit can be regenerated to the multi-level inverter side. For this reason, it is possible to suppress the leakage current passing through the surge suppression circuit to the ground while exhibiting the surge suppression effect not only for the symmetrical component of the surge voltage but also for the zero phase component of the surge voltage. Can be reduced.

Hereinafter, a surge suppression circuit according to an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a diagram showing a schematic configuration of an inverter drive motor system to which a surge suppression circuit according to a first embodiment of the present invention is applied.
In FIG. 1, the inverter drive motor system is provided with a converter 12 and an inverter 13. The inverter 13 is connected to a motor 15 through a cable 14, and a surge suppression circuit 16 is connected to the motor power receiving end T2. Yes. The inverter 13 may form a three-level inverter having a low potential point V _N of the high potential point V _P, the neutral point V _M and the DC voltage of the DC voltage of the DC voltage. Further, as the switching elements S11 to S22 provided in the converter 12 and the switching elements S51 to S62 provided in the inverter 13, for example, an IGBT (Insulated Gate Bipolar Transistor) or a power MOSFET can be used. .

Here, the surge suppression circuit 16 is provided with resistors RN1 to RN3 and capacitors CN1 to CN3. One end of a series circuit composed of these resistors RN1 to RN3 and capacitors CN1 to CN3 is connected to each phase of the motor receiving end T2, and the other end of these series circuits is connected to the DC voltage of the inverter 13. It is connected to the sexual point V _M.
Here, by connecting the other end of the series circuit of a surge suppression circuit 16 to the neutral point V _M of the DC voltage of the inverter 13, the ground point of the other end of the series circuit of a surge suppression circuit 16 is a commercial power supply at the same potential The leakage current I _{reakage that} has passed through the surge suppression circuit 16 is regenerated to the inverter 13 side. For this reason, it is possible to suppress the leakage current I _reakage flowing through the surge suppression circuit 16 from flowing to the ground while exerting the surge suppression effect not only on the symmetrical component of the surge voltage but also on the zero-phase component of the surge voltage. The leakage current I _reakage can be reduced.

FIG. 2 is a diagram showing another configuration example of the surge suppression circuit applied to the inverter drive motor system of FIG.
2 (a), the other end of the resistor RN1~RN3 and a series circuit comprising a capacitor CN1~CN3 surge suppression circuit 16a may be directly connected to the neutral point V _M of the DC voltage of the inverter 13 .

Further, in FIG. 2 (b), the other end of the resistor RN1~RN3 and a series circuit comprising a capacitor CN1~CN3 surge suppression circuit 16b is connected to the neutral point V _M of the DC voltage of the inverter 13 through capacitor CC You may make it do.
The connection in FIG. 2 (c), the other end of the resistor RN1~RN3 and a series circuit comprising a capacitor CN1~CN3 surge suppression circuit 16c via a resistor RC to the neutral point V _M of the DC voltage of the inverter 13 You may make it do.

Further, in FIG. 2D, the other end of the series circuit composed of the resistors RN1 to RN3 and the capacitors CN1 to CN3 of the surge suppression circuit 16d is the neutral point of the DC voltage of the inverter 13 through the resistor RC and the capacitor CC sequentially. You may be connected to V _M.
Here, for example, if the characteristic impedance of the symmetric component of the cable 14 is R _N0 and the characteristic impedance of the zero-phase component of the cable 14 is R _C0 , the configuration of FIG. If the impedance is matched with the characteristic impedance R _N0 , the values R _{N of the} resistors RN1 to RN3 are R _N = 2R _N0 / 3. In this case, the resistance value of the zero-phase component of the surge suppression circuit 16b is R _N / 3 (= 2R _N0 / 9).

Here, since the characteristic impedance of the cable 14 has a relationship of R _C0 > R _N0 , in the configuration of FIG. 2A, a complete impedance mismatch cannot be obtained for the zero-phase component (R _C0 / 3> R _N / 3 = 2R _N0 / 9).
On the other hand, FIG. In the arrangement of 2 (c), the value R _C of the resistor RC is (R _C0 -R _N) / 3 and the set to be such that, completely also the resistance value of the zero-phase component of the surge suppression circuit 16c Impedance mismatch can be obtained, and a high surge suppression effect can be expected for both the symmetric component and the zero-phase component.

In the configuration shown in FIG. 2 (b) or FIG. 2 (d), the so high surge suppression effect for both the symmetric component and the zero-phase components are obtained, it is arbitrarily determined value C _C of the capacitor CC it can.
In the embodiment of FIG. 1, the method of providing the converter 12 for converting alternating current to direct current has been described. However, as shown in FIG. 3, diode rectification configured by diodes D <b> 101 to D <b> 106 instead of the converter 12. A circuit 17 may be provided.
As the multi-level inverter, if those having a neutral point V _M at the other end can be connected DC voltage of the series circuit of a surge suppression circuit 16 may be a material other than the 3-level inverter.

1 is a diagram showing a schematic configuration of an inverter drive motor system to which a surge suppression circuit according to a first embodiment of the present invention is applied. It is a figure which shows the other structural example of the surge suppression circuit applied to the inverter drive motor system of FIG. It is a figure which shows schematic structure of the inverter drive motor system to which the surge suppression circuit which concerns on 2nd Embodiment of this invention is applied. It is a figure which shows schematic structure of the conventional inverter drive motor system. It is a figure which shows schematic structure of the inverter drive motor system to which the conventional surge suppression circuit is applied. It is a figure which shows the structural example of the inverter drive motor system to which the surge suppression circuit with which the suppression effect of the surge with respect to a zero phase component is acquired.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Transformer 12 Converter 13 Inverter 14 Cable 15 Motor 16, 16a-16d Surge suppression circuit 17 Diode rectifier circuit S11-S22, S51-S62 Switching element D11-S28, D51-D68, D101-D106 Diode C1, C2 DC capacitor CN1- CN3, CC capacitor RN1 to RN3, RC resistance T1 Inverter output terminal T2 Motor receiving terminal

Claims (4)

In the surge suppression circuit connected to the power receiving end of the motor supplied with power from the multi-level inverter via a cable,
The surge suppression circuit includes a series circuit in which a first resistor and a first capacitor whose values are set so as to reduce reflection due to impedance mismatch at the power receiving end of the motor are connected in series,
One end of the series circuit is connected to a power receiving end of the motor, and the other end of the series circuit is connected to a neutral point of a DC voltage of the multilevel inverter.   2. The surge suppression circuit according to claim 1, further comprising a second resistor or a second capacitor connected in series to the series circuit and having a value set so as to obtain impedance matching for a zero-phase component. . A multi-level inverter that supplies power to the motor;
A cable connecting the motor and the multi-level inverter;
A surge suppression circuit connected to the power receiving end of the motor,
The surge suppression circuit includes a series circuit in which a first resistor and a first capacitor whose values are set so as to reduce reflection due to impedance mismatch at the power receiving end of the motor are connected in series,
One end of the series circuit is connected to the power receiving end of the motor, and the other end of the series circuit is connected to a neutral point of the DC voltage of the multilevel inverter.   4. The inverter drive motor according to claim 3, further comprising a second resistor or a second capacitor connected in series to the series circuit and having a value set so as to obtain impedance matching for a zero-phase component. system.

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