JP2010252535A - Power conversion apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a power conversion apparatus that prevents an increase in resonance current by suppressing resonance of first/second capacitors during switching operation of switching elements of an inverter so as to eliminate the need to correspond to a large current, and consequently, to achieve miniaturization of the first/second capacitors. <P>SOLUTION: The power conversion apparatus includes: an inverter 6 for converting DC power supplied from a DC power supply 3 by switching operation of switching elements 7, 8 into AC power; a first capacitor 2 arranged on the side of the DC power supply 3 between connection wirings 4, 5; and a second capacitor 15 arranged on the side of the switching elements 7, 8. The equivalent inductances of the connection wirings 4, 5 and the electrostatic capacitance of the first capacitor 2 are set such that the resonance frequency determined by the equivalent inductances of the connection wirings 4, 5 and the electrostatic capacitance of the first capacitor 2 is matched with a frequency band of a high-frequency current superposed from the switching elements 7, 8 on the connection wirings 4, 5 during switching operation of the switching elements 7, 8. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a power conversion device that converts DC power into AC power by a switching operation of a switching element of an inverter.

  Conventionally, for example, an inverter connected to a DC power supply via a first capacitor as a power conversion device for supplying multiphase AC power converted by a switching operation of an inverter switching element to a multiphase AC motor And the power converter device of the structure provided with the 2nd capacitor | condenser arrange | positioned in the switching element vicinity of this inverter is known (for example, patent document 1).

JP 2004-254355 A

  By the way, in the configuration of the power conversion device of Patent Document 1, the capacitance of each of the first and second capacitors and the inductance of the connection wiring connecting the DC power supply and the switching element are divided. The capacitance of each of the second capacitors and the inductance of the connection wiring are reduced.

  For this reason, the resonance frequency determined by the product of these (capacitance, inductance) is increased, so that a high-frequency current (for example, about 1 kHz to 6 kHz) superimposed on the connection wiring from the switching element during the switching operation of the switching element of the inverter. The first and second capacitors resonate depending on the frequency band, and the resonance current flowing between the first and second capacitors and between the first capacitor and the DC power supply increases. Therefore, in order to cope with this increasing resonance current, it is necessary to increase the capacitance of the first and second capacitors, which causes the problem that the first and second capacitors are enlarged. .

  Therefore, the present invention suppresses the resonance of the first and second capacitors during the switching operation of the switching element of the inverter, prevents an increase in the resonance current, and eliminates the need to deal with a large current. It is an object of the present invention to provide a power converter that can reduce the size of the first and second capacitors.

  In order to achieve the above object, a power converter according to the present invention is connected to a DC power source through two connection wires, and converts DC power supplied from the DC power source into AC power by switching operation of a switching element. Inverter, provided in parallel with the DC power supply between the connection wires, a first capacitor disposed on the side close to the DC power supply, and provided in parallel with the DC power supply between the connection wires, And a second capacitor disposed on the side close to the switching element. The resonance frequency determined by the equivalent inductance of the connection wiring and the capacitance of the first capacitor is matched with the frequency band of the high-frequency current superimposed on the connection wiring from the switching element during the switching operation of the switching element. In addition, an equivalent inductance of the connection wiring and a capacitance of the first capacitor are set.

  According to the power conversion device of the present invention, it is determined by the set equivalent inductance and the capacitance of the first capacitor with respect to the frequency band of the high-frequency current superimposed from the switching element to the connection wiring during the switching operation of the switching element. By matching the resonance frequency, the impedance in the frequency band of the high-frequency current can be reduced. As a result, it is possible to suppress the resonance current from flowing between the first and second capacitors and between the first capacitor and the DC power supply, so that the capacitance of the first and second capacitors can be reduced. The size of the first and second capacitors can be reduced.

Schematic which shows the electric circuit structure of the power converter device which concerns on Embodiment 1 of this invention. The figure which shows the relationship between the frequency and impedance in Embodiment 1 of this invention. The figure which shows the relationship between the frequency and impedance in Embodiment 2 of this invention. Schematic which shows the electric circuit structure of the power converter device which concerns on Embodiment 3 of this invention. The figure which shows the relationship between the frequency and current ratio in Embodiment 3 of this invention. The figure which shows the relationship between the frequency and current ratio in Embodiment 4 of this invention.

Hereinafter, the present invention will be described based on the illustrated embodiments.
<Embodiment 1>
FIG. 1 is a schematic diagram illustrating an electric circuit configuration of a power conversion apparatus according to Embodiment 1 of the present invention.

  As shown in FIG. 1, the power conversion device 1 according to the present embodiment is connected to a DC power source 3 in which a first capacitor 2 is connected in parallel, and the DC power source 3 via two connection wires 4 and 5. The inverter 6 is provided. The first capacitor 2 is a smoothing capacitor and absorbs voltage fluctuations of the DC voltage supplied from the DC power source 3 to the inverter 5.

  The inverter 6 has switching elements 7 and 8 of the upper and lower arms connected in series for three phases between the two connection wires 4 and 5, and PWM (a predetermined carrier frequency PWM ( Based on the (pulse width modulation) signal, the switching power of the switching elements 7 and 8 is controlled to convert the DC power supplied from the DC power supply 3 into three-phase AC power. By supplying the three-phase AC power generated by the inverter 6 to each phase (U phase, V phase, W phase) of the three-phase AC motor 10, the three-phase AC motor 10 is driven at a desired rotational speed. . The three-phase AC motor 10 is a travel drive motor installed in a drive system such as an electric vehicle or a hybrid vehicle.

  Diodes 11 and 12 are connected in parallel to the switching elements 7 and 8 of each phase. Further, a second capacitor 13 is connected in parallel with the switching elements 7 and 8 between the connection wires 9 and 10 on the inverter 6 side. The second capacitor 13 absorbs a surge voltage generated when the switching elements 7 and 8 are turned on / off. As the switching elements 7 and 8, for example, MOS-FETs can be used.

  In the electric circuit of the power conversion device 1 according to the present embodiment shown in FIG. 1, an equivalent inductance L1 exists in the line (connection wiring) between the first capacitor 2 and the second capacitor 13, and the first The equivalent inductance L2 exists in the line (connection wiring) between the capacitor 2 and the DC power source 3. In the present embodiment, the value of the equivalent inductance L1 is made smaller than the value of the equivalent inductance L2. Specifically, the equivalent inductance L1 is set to 2 μH, and the equivalent inductance L2 is set to 10 μH.

  Further, the capacitance C1 of the first capacitor 2 is set to 500 μF, and the capacitance C2 of the second capacitor 13 is set to 300 μF. Furthermore, in this embodiment, the carrier frequency input from the control unit 9 for driving the inverter 6 is set to 1 kHz, and the internal resistance of the DC power supply 3 is set to 200 mΩ.

  By the way, as described above, the frequency band (for example, 1 kHz to 6 kHz) of the high-frequency current (ripple current) superimposed on the line (connection wiring) from the switching elements 7 and 8 during the switching operation of the switching elements 7 and 8 of the inverter 6. About 1), a resonance phenomenon occurs in each of the first and second capacitors 2 and 13 connected in parallel, resulting in a problem that the impedance increases.

  For this reason, in this embodiment, in the electric circuit of the power converter 1, the resonance frequency (1 / 2π√ (L1C1)) determined by the equivalent inductance L1 and the capacitance C1 of the first capacitor 2 is set to each of the inverters 6. A predetermined frequency band of a high-frequency current (ripple current) superimposed on the line (connection wiring) from the switching elements 7 and 8 during the switching operation of the switching elements 7 and 8 (for example, in the range of 1 kHz to 7 kHz in the present embodiment). The equivalent inductance L1 and the capacitance C1 of the first capacitor 2 are set so as to match the desired frequency band.

  That is, according to the power conversion apparatus 1 of the present embodiment, as shown in FIG. By adjusting the set equivalent inductance L1 and the resonance frequency determined by the capacitance of the first capacitor 2 to the frequency band of current (ripple current) (in FIG. 2, frequency f (about 7 kHz), the high-frequency current The impedance in the frequency band of (ripple current) (in FIG. 2, the frequency f (about 7 kHz) can be reduced.

  The impedance in this frequency band can be further reduced by setting the resistance value in the line (connection wiring) portion of the equivalent inductance L1 and the resistance value in the first capacitor 2 to be small.

  Therefore, the occurrence of a resonance phenomenon in the first and second capacitors 2 and 15 is suppressed in a predetermined frequency band (in FIG. 2, frequency f (about 7 kHz) in the high-frequency current (ripple current). This suppresses the resonance current from flowing between the first and second capacitors 2 and 15 and between the first capacitor 2 and the DC power supply 3. Since the capacity can be reduced, the first and second capacitors 2 and 15 can be reduced in size.

  In the present embodiment, the carrier frequency input from the control unit 11 for driving the inverter 6 is 1 kHz, and the resonance frequency determined by the above-described equivalent inductance L1 and the capacitance of the first capacitor 2 (FIG. 2). Is set to be smaller than a predetermined frequency band (frequency f) of the high-frequency current shown in FIG.

  In FIG. 2, the frequency f1 is a resonance frequency determined by the equivalent inductance L1 and the capacitances C1 and C2 of the first and second capacitors 2 and 15.

<Embodiment 2>
In the present embodiment, in the electric circuit of the power conversion apparatus 1 shown in FIG. 1, the equivalent inductance L1 is set to be smaller than that in the first embodiment (the line (connection wiring) length of the equivalent inductance L1 is shortened). is there. Other configurations are the same as those of the first embodiment, and redundant description is omitted. In the present embodiment, the equivalent inductance L1 is set to 1 μH, and the equivalent inductance L2 is set to 11 μH.

  Thus, by setting the equivalent inductance L1 to be smaller than that in the case of the first embodiment, the resonance frequency determined by the equivalent inductance L1 and the capacitance of the first capacitor 2 is the same as that of the first embodiment shown in FIG. It becomes possible to set higher than the case.

  In the present embodiment, the resistance value in the line (connection wiring) portion of the equivalent inductance L1 and the resistance value in the first capacitor 2 are set to be smaller than those in the first embodiment.

  Thereby, as shown in FIG. 3, in the predetermined frequency band (in FIG. 3, frequency f (about 8 kHz) of the high-frequency current (ripple current) superimposed on the line (connection wiring) from the switching elements 7 and 8 described above. Can be made even smaller than in the case of the first embodiment shown in FIG.

<Embodiment 3>
As shown in FIG. 4, the power conversion device 1 a according to the present embodiment increases the predetermined carrier frequency input from the control unit 9 for driving the inverter 6 to 20 kHz and rotates the three-phase AC motor 10 at a high speed. This is the case. Other configurations are the same as those of the first embodiment, and redundant description is omitted.

  In this embodiment, the equivalent inductance L1 is 2 μH, the equivalent inductance L2 is 10 μH, the capacitance C1 of the first capacitor 2 is 500 μF, the capacitance C2 of the second capacitor 13 is 300 μF, and the DC power supply 3 The internal resistance is set to 200 mΩ.

  In the present embodiment, in the electric circuit of the power conversion device 1a shown in FIG. 4, the resonance frequency determined by the equivalent inductance L1 and the capacitances of the first and second capacitors 2 and 13 is set to each switching element of the inverter 6. 7 and 8 so as to be larger than the frequency band of the high-frequency current (ripple current) superimposed on the line (connection wiring) from the switching elements 7 and 8 during the on / off operation, and smaller than the carrier frequency, The equivalent inductance L1 and the capacitances of the first and second capacitors 2 and 15 are selected.

  That is, according to the power conversion device 1a of the present embodiment, as shown in FIG. 5, the frequency band B of the resonance frequency determined by the equivalent inductance L1 and the capacitances of the first and second capacitors 2 and 13 is Frequency band A (about 1 kHz to 7 kHz of the frequency shown in FIG. 5) of the high-frequency current (ripple current) superimposed on the line (connection wiring) from the switching elements 7 and 8 when the switching elements 7 and 8 of the inverter 6 are turned on / off. The equivalent inductance L1 and the electrostatic capacitances of the first and second capacitors 2 and 13 are set so as to be larger than the carrier frequency f2 (20 kHz in the present embodiment). By selecting, the resonance current is suppressed from flowing between the first and second capacitors 2 and 13 and between the first capacitor 2 and the DC power supply 3. 1, by being able to reduce the capacitance of the second capacitor 2 and 13, first, the miniaturization of the second capacitor 2,13 becomes possible.

  In FIG. 5, the vertical axis indicates the current ratio (DC power supply 3 for the high-frequency current (ripple current) superimposed on the line (connection wiring) from the switching elements 7 and 8 when the switching elements 7 and 8 of the inverter 6 are turned on and off. Ratio of high-frequency current flowing through the

<Embodiment 4>
In this embodiment, in the electric circuit of the power conversion device 1a shown in FIG. 4, the equivalent inductance L1 is set to be smaller than that in the third embodiment (the line (connection wiring) length of the equivalent inductance L1 is shortened). is there. Other configurations are the same as those of the third embodiment, and redundant description is omitted. In this embodiment, the equivalent inductance L1 is set to 1 μH, the equivalent inductance L2 is set to 11 μH, and the total equivalent inductance is the same as that of the third embodiment.

  As described above, by setting the equivalent inductance L1 to be smaller than that in the third embodiment, the equivalent inductance L1 and the capacitances of the first and second capacitors 2 and 13 are determined as shown in FIG. The frequency band B of the resonance frequency can be set higher than in the case of the third embodiment shown in FIG.

  Further, in addition to setting the equivalent inductance L1 to be small, the frequency band B of the resonance frequency is set to be higher by setting the difference in capacitance between the first and second capacitors 2 and 13 large. be able to.

  In this embodiment, the frequency band B of the resonance frequency is increased by increasing the resistance value in the line (connection wiring) portion of the equivalent inductance L1 and the resistance values in the first and second capacitors 2 and 13. It becomes possible to make it narrow. By narrowing the frequency band B of the resonance frequency, the influence range of the resonance frequency B can be narrowed.

DESCRIPTION OF SYMBOLS 1, 1a Power converter device 2 1st capacitor | condenser 3 DC power supply 6 Inverter 7, 8 Switching element 11 Control part 12 3-phase alternating current motor 15 2nd capacitor | condenser

Claims (4)

An inverter connected to a DC power source via two connection wires, and converting DC power supplied from the DC power source into AC power by switching operation of a switching element;
A first capacitor provided in parallel with the DC power supply between the connection wirings and disposed on the side close to the DC power supply;
A second capacitor provided in parallel with the DC power source between the connection wirings and disposed on the side close to the switching element,
The resonance frequency determined by the equivalent inductance of the connection wiring and the capacitance of the first capacitor is matched with the frequency band of the high-frequency current superimposed on the connection wiring from the switching element during the switching operation of the switching element. A power conversion device, wherein an equivalent inductance of the connection wiring and a capacitance of the first capacitor are set.   The equivalent inductance between the first capacitor and the second capacitor of the connection wiring is made smaller than the equivalent inductance between the DC power source of the connection wiring and each of the first capacitors. The power converter according to 1. An inverter connected to a DC power source via two connection wires, and converting DC power supplied from the DC power source into AC power by switching operation of a switching element;
A first capacitor provided in parallel with the DC power supply between the connection wirings and disposed on the side close to the DC power supply;
A second capacitor provided in parallel with the DC power source between the connection wirings and disposed on the side close to the switching element,
The resonance frequency determined by the equivalent inductance and the capacitances of the first and second capacitors is larger than the frequency band of the high-frequency current superimposed on the connection wiring from the switching element during the switching operation of the switching element. And the equivalent inductance of the connection wiring and each of the first and second capacitors so as to be smaller than the carrier frequency for driving the switching element input from the control unit to the power converter. A power converter characterized by setting an electrostatic capacity.   The equivalent inductance between the first capacitor and the second capacitor of the connection wiring is made smaller than the equivalent inductance between the DC power source of the connection wiring and each of the first capacitors. 4. The power conversion device according to 3.

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