JP5515332B2 - Power converter - Google Patents

Description

  The present invention belongs to the technical field of power converters.

  2. Description of the Related Art Conventionally, an inverter connected to a DC power supply via a first smoothing capacitor and a second smoothing capacitor disposed on the inverter side are provided, and the capacitance of the second smoothing capacitor is set to the first smoothing capacitor. There is disclosed a power conversion device that is smaller than the electrostatic capacity and has a high-frequency impedance equal to or less than that.

JP 2004-254355 A

  However, conventionally, the capacitor on the inverter side and the capacitor on the power source side resonate, and the current flowing through the capacitor increases. In order to cope with this current, the capacitor may be increased in size.

  The present invention has been made paying attention to the above problems, and an object of the present invention is to provide a power converter capable of suppressing a current flowing in a capacitor due to resonance.

In order to achieve the above object, in the present invention, capacitors are provided in parallel on the power supply side and the switching element side, respectively, and the inductance of the DC power line connecting the capacitor on the switching element side and the switching element is set to the capacitor on the switching element side. While making it smaller than the inductance of the DC power line connecting to the DC power source, the capacitance of the capacitor on the power source side was made smaller than the capacitance of the capacitor on the switching element side.

  Therefore, in the present invention, the resonance frequency of the circuit on the power supply side and the resonance frequency of the circuit on the switching element side are compared with the case where the capacitance of the capacitor on the power supply side is larger than the capacitance of the capacitor on the switching element side. Therefore, the current flowing through the capacitor due to resonance can be suppressed.

It is explanatory drawing which shows the schematic circuit structure of the power converter of Example 1. FIG. 3 is a graph showing frequency characteristics of each part impedance and each part current in Example 1. FIG. It is a graph which shows the frequency characteristic of each part impedance and each part current in Example 2. It is explanatory drawing which shows schematic circuit structure of the power converter of Example 3. FIG. It is explanatory drawing which shows schematic circuit structure of the power converter of Example 4. FIG. It is explanatory drawing which shows schematic circuit structure of the power converter of Example 5. FIG.

  Hereinafter, embodiments for realizing the power converter of the present invention will be described.

First, the configuration will be described.
FIG. 1 is an explanatory diagram illustrating a schematic circuit configuration of the power converter according to the first embodiment.
The power converter according to the first embodiment has a configuration in which a DC power source B and a power conversion unit 101 are connected by two DC power lines 301.
As a specific example, the power conversion unit 101 is an inverter used for motor control or the like, and has, for example, a switching element bridge configuration to output a three-phase alternating current. FIG. 1 shows a schematic configuration for one phase. The power conversion unit 101 includes a power module SW and a power module SW in which a first capacitor C1 is connected in parallel via a DC power line 301.
The power module SW performs AC output for one phase. Specifically, the power module SW has an upper and lower bridge configuration for the switching element.

The first capacitor C1 is connected in parallel with the power module SW, and forms a low impedance circuit with the power module SW. The first capacitor C1 reduces the ripple current on the power conversion unit 101 side.
Next, in the power conversion unit 101, the inductance of the DC power line 301 connecting the power module SW and the first capacitor C1 is set as an inductance L1 (not shown in FIG. 1). Further, a resistance component in the power conversion unit 101 is a resistance R1 (not shown in FIG. 1).
A DC power source B that supplies power to the power conversion unit 101 by DC is provided with a second capacitor C2 connected in parallel via a DC power line 301. The second capacitor C2 reduces the ripple current on the DC power supply B side.
Next, the inductance of the DC power line 301 connecting the DC power supply B and the power conversion unit 101 is defined as an inductance L2. A resistance component on the side of the DC power supply B with respect to the power conversion unit 101 is a resistance R2 (not shown in FIG. 1). The inductances L1 and L2 of the DC power line 301 have a relationship of L2> L1 because the inductance L1 is on the low impedance circuit side.
The capacitance C1 of the first capacitor C1 (denoted by the same symbol) and the capacitance C2 of the second capacitor C2 (denoted by the same symbol) have a relationship of C1> C2.

The operation will be described.
[Resonant current suppression]
In the power converter of the first embodiment, the harmonics generated by the power module SW are determined by the ratio of the impedance Z1 of the capacitor side circuit and the impedance Z2 on the DC power supply B side at each frequency (several kHz carrier frequency in the power conversion unit 101). The ripple current is shunted. Then, a part of current tries to flow into the DC power source B.
In the first embodiment, the second capacitor C2 having a lower impedance than the DC power supply B is provided in parallel connection on the DC power supply B side. For this reason, the shunted ripple current is smoothed toward the second capacitor C2, so that the ripple current of the DC power source B is reduced. Therefore, the loss generated in the DC power supply B due to the harmonic ripple current flowing in is reduced. This will improve system efficiency.

Furthermore, in the first embodiment, the capacitances C1 and C2 of the first capacitor C1 and the second capacitor C2 have a relationship of C1> C2. Inductances L1 and L2 in series with this have a relationship of L2> L1. Therefore, the series resonance frequency of the circuit on the DC power supply B side approaches the series resonance frequency of the circuit on the first capacitor C1 side. Then, the generation of resonance current due to the wiring inductance between the circuit on the DC power supply B side and the circuit on the first capacitor C1 side (power conversion unit 101) is suppressed.
Therefore, it is possible to reduce the capacitances of the first capacitor C1 and the second capacitor C2 that absorb the respective ripple currents that have been shunted. This contributes to miniaturization of the power converter.
Further, in the power converter according to the first embodiment, since the inductances L1 and L2 of the DC power line 301 are taken into consideration, it is possible to reduce the required capacitance in the entire configuration circuit, and downsize each capacitor. .

The operation of the first embodiment will be further described with reference to FIG.
FIG. 2 is a graph showing the frequency characteristics of each part impedance and each part current in Example 1.
FIG. 2 shows a case where the DC power source B is 500 mΩ, the resistor R1 is 30 mΩ, the inductance L1 is 100 nH, the capacitor capacitance C1 is 1200 μF, the resistor R2 is 30 mΩ, the inductance L2 is 2100 mH, and the capacitor capacitance C2 is 800 μF. The relationship of C1> C2 is satisfied.
The DC power supply B side has a constant characteristic up to 10 kHz at 500 mΩ of the DC power supply B, and becomes a characteristic of the wiring inductance L2 above 10 kHz.

FIG. 2A shows the frequency characteristics of the impedance. Reference numeral 201 denotes the characteristic (Z1) of the circuit (power conversion unit 101) on the first capacitor C1 side, and characteristic (Z2) of the circuit on the DC power supply B side. Is denoted by reference numeral 202, and a combination of the characteristics of both circuits (Z1 + Z2) is denoted by reference numeral 203.
FIG. 2B shows the frequency characteristics of the ripple current. The current (i1) on the first capacitor C1 side is denoted by reference numeral 204, the current (i2) on the DC power supply B side is denoted by reference numeral 205, and the combined current of both currents. (i1 + i2) is denoted by reference numeral 206.
By configuring the power converter to have a relationship of C1> C2, as shown in FIG. 2A, the impedance 201 on the first capacitor C1 side (power conversion unit 101) and the impedance on the DC power supply B side are provided. In 202, the distribution ratio is changed to an optimized frequency characteristic.
As a result, the frequency characteristics of the ripple current of the current (i1) 204 on the first capacitor C1 side and the current (i2) 205 on the DC power supply B side are optimized as shown in FIG. The increase due to the resonance current is suppressed.

Next, the effect will be described.
The power converter according to the first embodiment has the effects listed below.
(1) Two DC power lines 301 for supplying power from the DC power source B, a power module SW having a switching element for performing a switching operation for converting power from the DC power line 301, and a switching element provided in the DC power line 301 A first capacitor C1 disposed on the DC power line 301 and a second capacitor C2 disposed on the DC power supply B side, the capacitance of the second capacitor C2 on the DC power supply B side Is smaller than the capacitance of the first capacitor C1 on the switching element side, so that the resonance frequency of the circuit composed of the DC power supply B and the second capacitor C2 and the circuit composed of the power module SW and the first capacitor C1 are reduced. The resonance frequency can be made close, and the current flowing through the first capacitor C1 and the second capacitor C2 can be suppressed by resonance. For this reason, it is not necessary to deal with a large current, and the increase in size of the first capacitor C1 and the second capacitor C2 can be suppressed.

  (2) Since the impedance of the second capacitor C2 is made smaller than the impedance of the DC power supply B, the harmonic ripple current directed to the DC power supply B can be taken into the second capacitor C2 and the ripple current can be reduced.

In the second embodiment, the product of the inductance L1 on the first capacitor side and the capacitance of the first capacitor C1 is substantially the same as the product of the inductance L2 on the DC power source side and the capacitance of the second capacitor C2. .
The configuration will be described.
The schematic circuit configuration of the power converter according to the second embodiment is the same as that shown in FIG.
In the second embodiment, the product of the capacitance C1 of the first capacitor and the inductance L1 of the DC power line 301 of the power converter 101 is the inductance L2 of the capacitance C2 of the second capacitor and the DC power line 301 on the DC power supply B side. Are substantially the same. In other words, the configuration satisfies C1 × L1≈C2 × L2.
However, the impedance of the second capacitor C2 arranged on the DC power supply B side is made smaller than the impedance of the DC power supply B at the carrier frequency (for example, 1 kHz) that is the drive frequency of the switching element provided in the power module SW.
Since other configurations are the same as those of the first embodiment, the description thereof is omitted.

The operation will be described.
[Resonant current suppression]
In the second embodiment, the series resonance frequency on the DC power supply B side and the series resonance frequency on the first capacitor side (power conversion unit 101) are matched so as to satisfy C1 × L1≈C2 × L2. Therefore, the generation of resonance current due to the wiring inductance between the circuit on the DC power supply B side and the circuit on the first capacitor C1 side (power conversion unit 101) is most suppressed.
Therefore, it is possible to minimize the current tolerance (capacitance) of the first capacitor C1 and the second capacitor C2 that absorb the respective ripple currents that have been shunted. In the second embodiment, both satisfying C1 × L1≈C2 × L2 and making the impedance of the second capacitor C2 on the DC power supply B side smaller than the impedance of the DC power supply B are compatible. As a result, the harmonic ripple current toward the DC power source B is taken into the second capacitor C2 and the ripple current is reduced while maximizing the action of suppressing the resonance current.

The operation of the second embodiment will be described with reference to FIG.
FIG. 3 is a graph showing the frequency characteristics of each part impedance and each part current in Example 2.
FIG. 3 shows a case where the DC power source B is 500 mΩ, the resistor R1 is 30 mΩ, the inductance L1 is 100 nH, the capacitor capacitance C1 is 1000 μF, the resistor R2 is 30 mΩ, the inductance L2 is 2100 mH, and the capacitor capacitance C2 is 500 μF. C1 × L1 ≒ C2 × L2 is satisfied.
Then, as shown in FIG. 3 (a), the impedance 201 on the first capacitor C1 side (power conversion unit 101) and the impedance 202 on the DC power supply B side have the best distribution ratio in terms of frequency characteristics. To be optimized.
As a result, as shown in FIG. 3 (b), the frequency characteristic of the ripple current of the current (i1) 204 on the first capacitor C1 side and the current (i2) 205 on the DC power supply B side is optimal for the best state. And the increase of the ripple current due to the resonance current is most reduced.
Since other operations are the same as those of the first embodiment, description thereof is omitted.

Explain the effect. The power converter according to the second embodiment has the following effects in addition to the effects (1) and (2) of the first embodiment.
(3) The product of the capacitance C1 of the first capacitor and the inductance L1 of the DC power line 301 on the switching element side of the power module SW is the inductance of the capacitance C2 of the second capacitor and the DC power line 301 on the DC power source B side. Since it is almost the same as the product of L2, the resonance frequency of the circuit composed of the DC power supply B and the second capacitor C2 and the resonance frequency of the circuit composed of the power module SW and the first capacitor C1 are made substantially the same. And the current flowing through the first capacitor C1 and the second capacitor C2 can be most suppressed by resonance. For this reason, the enlargement of the 1st capacitor | condenser C1 and the 2nd capacitor | condenser C2 can be suppressed most.

  (4) Since the impedance of the second capacitor C2 is smaller than the impedance of the DC power supply B in the frequency band of 1 kHz to 100 kHz, the switching frequency of the switching element provided in the power module SW and the carrier frequency are higher than the impedance of the DC power supply B. The impedance of the two capacitors C2 is reduced, and in the frequency band to be used, the harmonic ripple current toward the DC power source B can be taken into the second capacitor C2 to reduce the ripple current.

The third embodiment is an example in which the DC power source B and the second capacitor are integrated.
The configuration will be described.
FIG. 4 is an explanatory diagram illustrating a schematic circuit configuration of the power converter according to the third embodiment.
In the power converter according to the third embodiment, the DC power supply B and the second capacitor C2 provided in parallel with the DC power supply B are integrated into a module 302.
Other configurations are the same as those of the first embodiment, and thus the description thereof is omitted.

The operation will be described.
In the third embodiment, since the DC power source B and the second capacitor C2 are integrated, when configuring a circuit for connecting the DC power source B to the power conversion unit 101, a circuit having the second capacitor C2 must be provided separately. Omitted.
Since other operations are the same as those of the first embodiment, description thereof is omitted.

Explain the effect. The third embodiment has the following effects in addition to the effects (1) and (2) of the first embodiment and the effects (3) and (4) of the second embodiment.
(5) Since the second capacitor C2 is the module 302 integrated with the DC power source B, it is possible to suppress an increase in the number of circuits having the second capacitor C2, thereby suppressing an increase in cost and an increase in the size of the apparatus.

The fourth embodiment is an example in which the second capacitor is integrated with the circuit breaker.
The configuration will be described.
FIG. 5 is an explanatory diagram illustrating a schematic circuit configuration of the power converter according to the fourth embodiment.
In the power converter according to the fourth embodiment, a circuit breaker 303 that cuts off the power supply from the DC power source B to the power converter 101 when a predetermined condition occurs is provided.
And the circuit breaker 303 is provided with the 2nd capacitor | condenser C2 connected in parallel with the interruption | blocking part S which interrupts | blocks the electric power from DC power supply B, and the interruption | blocking part S. FIG. That is, the circuit breaker 303 and the second capacitor C2 are integrated.
Other configurations are the same as those of the first embodiment, and thus the description thereof is omitted.

The operation will be described.
In the fourth embodiment, the circuit breaker 303 and the second capacitor C2 are integrated. Therefore, when the power converter includes the circuit breaker, a separate circuit having the second capacitor C2 is omitted.
Since other operations are the same as those of the first embodiment, description thereof is omitted.

Explain the effect. The fourth embodiment has the following effects in addition to the effects (1) and (2) of the first embodiment and the effects (3) and (4) of the second embodiment.
(6) Since the second capacitor C2 is integrated with the circuit breaker 303 that cuts off the power supply of the DC power supply B, it is possible to suppress an increase in the number of circuits having the second capacitor C2, thereby suppressing an increase in cost and an increase in size of the apparatus. Can do.

Example 5 is an example in which the second capacitor is integrated with the connector.
The configuration will be described.
FIG. 6 is an explanatory diagram illustrating a schematic circuit configuration of the power converter according to the fifth embodiment.
In the power converter according to the fifth embodiment, a connector 304 for connection is provided in the middle of the DC power line 301 that connects the DC power supply B and the power converter 101.
The connector 304 includes a connection part CN that connects the middle of the DC power line 301 and a second capacitor C2 that is connected in parallel with the connection part CN. That is, the connector 304 and the second capacitor C2 are integrated.
Other configurations are the same as those of the first embodiment, and thus the description thereof is omitted.

The operation will be described.
In the fifth embodiment, since the connector 304 and the second capacitor C2 are integrated, when the power converter is configured to connect the DC power source B and the power converter 101 with the connector, a circuit having the second capacitor C2 is provided. A separate provision is omitted.
Since other operations are the same as those of the first embodiment, description thereof is omitted.

Explain the effect. The fifth embodiment has the following effects in addition to the effects (1) and (2) of the first embodiment and the effects (3) and (4) of the second embodiment.
(7) Since the second capacitor C2 is integrated with the connector 304 for connecting the DC power line 301, it is possible to suppress an increase in the number of circuits having the second capacitor C2, thereby suppressing an increase in cost and an increase in the size of the apparatus.

The semiconductor device according to the present invention has been described based on the first to fifth embodiments. However, the specific configuration is not limited to these embodiments, and the claims relate to each claim. Design changes and additions are allowed without departing from the scope of the invention.
For example, the capacitors C1 and C2 and the inductance L2 described in FIG. 1 may each indicate a component of the circuit component.

  The present invention can be used for other power devices.

101 Power converter
301 DC power line
302 modules
303 circuit breaker
304 connector
B DC power supply
C1 1st capacitor
C2 Second capacitor
CN connection
L1 inductance
L2 inductance
R1 resistance
R2 resistance
S block
SW power module

Claims (7)

It has two DC power lines that supply power from the DC power supply to the power converter ,
Wherein a switching element for switching operation the power conversion unit converts the power from the DC power line, and a first capacitor arranged in parallel to the switching element via the DC power line,
Before Symbol DC power supply arranged in parallel a second capacitor through the DC power line,
The inductance of the DC power line connecting the first capacitor and the switching element is made smaller than the inductance of the DC power line connecting the power conversion unit and the DC power supply,
The power converter, wherein a capacitance of the second capacitor on the DC power source side is made smaller than a capacitance of the first capacitor on the switching element side. It has two DC power lines that supply power from the DC power supply to the power converter,
Wherein a switching element for switching operation the power conversion unit converts the power from the DC power line, and a first capacitor in parallel placed on the switching element via the DC power line,
A second capacitor is disposed in parallel to the DC power source via the DC power line ,
The product of the inductance of the DC power line capacitance and the power conversion unit of the first capacitor, and substantially the same as the product of the inductance of the second electrostatic capacitance of the capacitor and the DC power supply side of the DC power line, A power converter characterized by that. The power converter according to claim 1 or 2,
The power converter, wherein the second capacitor is integrated with the DC power source. The power converter according to claim 1 or 2,
The power converter, wherein the second capacitor is integrated with a circuit breaker that cuts off the power supply of the DC power supply. The power converter according to claim 1 or 2,
The power converter, wherein the second capacitor is integrated with a connector for connecting the DC power line. The power converter according to any one of claims 1 to 5,
The power converter characterized in that the impedance of the second capacitor is made smaller than the impedance of the DC power supply. The power converter according to any one of claims 1 to 5,
The power converter characterized in that the impedance of the second capacitor is smaller than the impedance of the DC power supply in a frequency band of 1 kHz to 100 kHz.

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