JP2009278794A - Power conversion apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To equalize a temperature of a smoothing capacitor of a power conversion apparatus by a simpler technology. <P>SOLUTION: The power conversion apparatus comprises a step-up converter which boosts a power supply voltage, an inverter which converts a DC power boosted by the step-up converter into an AC power, and a smoothing capacitor C and a discharge resistor R connected in parallel to a power supply line to the inverter. The smoothing capacitor C is housed in a capacitor container 2 as a module in which a plurality of capacitor elements C1 are connected parallel between a high potential side busbar P and a low potential side busbar N provided to the power supply line. The discharge resistor R is housed in a relatively low temperature region of the capacitor container 2. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a power converter for a vehicle, and relates to a power converter including an inverter that converts DC power into AC power and supplies the AC power to a load.

  In a hybrid vehicle and an electric vehicle, DC power generated from a secondary battery is converted into AC power, and a motor that is an AC load is driven. As a power conversion device that performs direct current (DC) -alternating current (AC) conversion, for example, a power conversion device including an inverter constituted by an IGBT (Insulated Gate Bipolar Transistor) is used. In such a power conversion device, a smoothing capacitor is incorporated in a wiring portion (DC input side) that supplies power to the inverter for the purpose of suppressing power supply ripple generated on the power supply side during switching of the inverter.

  Patent Document 1 discloses a power conversion device having a configuration incorporating such a smoothing capacitor. The power conversion device of Patent Document 1 includes a boost converter (DC-DC converter) that boosts a power supply voltage generated from a secondary battery (DC power supply), and the power supply voltage boosted to a predetermined voltage by the boost converter. Apply to inverter (DC-AC converter). A smoothing capacitor and a discharge resistor are connected in parallel to the power supply line from the boost converter to the inverter. The discharge resistor is provided to discharge the electric charge accumulated in the smoothing capacitor.

FIG. 3 shows an assembly example of the power conversion device. In the illustrated power converter, a smoothing capacitor that is modularized by connecting a plurality of capacitor elements 1 in parallel between bus bars is housed in a dedicated capacitor container 2. And the housing 3 which accommodated the boost converter, the inverter, and the discharge resistance is assembled on the upper part of the capacitor container 2.
JP 2006-042498 A (FIG. 11)

  In a vehicle power conversion device, since the load drive current is large, the size of the smoothing capacitor becomes large if an attempt is made to obtain a necessary capacity with a single element. Therefore, as shown in FIG. 3, a smoothing capacitor is configured as a module in which a plurality of capacitor elements are arranged in a matrix and connected in parallel between a high potential bus bar and a low potential bus bar connected to the power supply line. It is housed in one capacitor container and incorporated into the power converter.

  In such a smoothing capacitor in a power converter, the ripple current flowing into the capacitor element causes an increase in the element temperature. The degree of the temperature increase depends on the connection position of a large number of capacitor elements arranged between the bus bars. It is known to be different. Since the difference in temperature causes a difference in deterioration of the capacitor element, measures are taken such as changing the capacity of the capacitor element depending on the location or devising a cooling structure in order to make the temperature as uniform as possible. However, it is disadvantageous in cost to change the capacity depending on the location or to devise the cooling structure, and improvement by a simpler method is desired.

  This invention pays attention to this point, and makes it possible to equalize the temperature of the smoothing capacitor in the power converter by a simple method.

  A power converter according to the present invention is connected to a boost converter that boosts a power supply voltage, an inverter that converts DC power boosted by the boost converter into AC power, and a power supply line from the boost converter to the inverter. And a discharge resistor connected in parallel with the smoothing capacitor to the power supply line. In the present invention, the smoothing capacitor is configured as a module in which a plurality of capacitor elements are connected in parallel between a high potential side bus bar and a low potential side bus bar connected to the power supply line, and is stored in a capacitor container. The discharge resistance is accommodated in a relatively low temperature region in the capacitor container.

  The discharge resistance is a heating element because the resistance value is increased to suppress loss. Therefore, by installing this discharge resistor in a relatively low temperature region in the capacitor container, the temperature of the region can be increased and the temperature in the container can be balanced. That is, the temperature of the smoothing capacitor can be made uniform by a simple method of simply disposing the discharge resistor in the capacitor container.

  FIG. 1 is a block diagram showing an embodiment of a power conversion device according to the present invention. As shown in the figure, the power conversion device of this embodiment uses a secondary battery BAT as a DC power supply, and has a configuration in which the power supply voltage of the secondary battery BAT is boosted to a predetermined voltage by a boost converter CNV. The boosted DC power is converted into AC power by the inverter INV and supplied to the AC load AL provided with a vehicle driving motor.

  In the power converter of this embodiment, the smoothing capacitor C and the discharge resistor R are connected in parallel to a power supply line that supplies DC power from the boost converter CNV to the inverter INV. Specifically, as shown in FIG. 2, the smoothing capacitor C is connected in parallel by arranging a plurality of capacitor elements C1 in a matrix between the high potential side bus bar P and the low potential side bus bar N connected to the power supply line. The discharge resistor R is connected to a region on the side opposite to the power source side (side connected to the inverter INV) with respect to the bus bars P and N.

  The discharge resistor R according to this embodiment shown in FIG. 2A is different from the conventional structure in that it is housed in the capacitor container 2 indicated by a dotted line. That is, the smoothing capacitor C of the present embodiment is configured as a module in which a plurality of capacitor elements C1 are connected in parallel between the bus bars P and N as described above, and is accommodated in the capacitor container 2, and the discharge resistance R is disposed in a region of the capacitor container 2 having a relatively low temperature, that is, in the case of this embodiment, the end of the bus bar P, N opposite to the power supply side.

  The high frequency ripple current generated by the operation of the boost converter CNV with respect to the bus bars P and N is concentrated on the capacitor element C1-A on the power source side by the inductance component of the bus bars P and N. Accordingly, the ripple current flowing through the capacitor element C1-A tends to be larger than the ripple current flowing through the capacitor element C1-D on the opposite side, and as a result, the temperature rise of the capacitor element C1-A is increased. Larger than other elements. That is, a temperature imbalance occurs in the capacitor container 2, and the temperature of the bus bars P and N on the side opposite to the power supply side is lower than that in other regions.

  The discharge resistor R provided for discharging the smoothing capacitor C generates heat because its resistance value is increased to suppress loss. Therefore, the discharge resistance R is arranged in a relatively low temperature region in the capacitor container 2, that is, in the embodiment of FIG. 2, at the end opposite to the power supply side of the bus bars P and N, thereby balancing the temperature in the container. Can be achieved. Therefore, the temperature of the smoothing capacitor C can be made uniform without changing the capacitance of the capacitor element C1 depending on the location or without special measures in the cooling structure of the smoothing capacitor C. As a result, the deterioration over time of the capacitor element C1 can be equalized regardless of the location.

  The electrical connection (wiring) of the discharge resistor R may be on the power source side of the bus bars P and N or on the opposite side, and the arrangement of the discharge resistor R in the container is on the side opposite to the power source side of the bus bars P and N. That's fine.

  FIG. 2B shows an example in which the discharge resistance R ′ using an NTC (Negative Temperature Coefficient) thermistor is arranged in the same region as the embodiment of FIG. An NTC thermistor is a device whose resistance value decreases as the element temperature increases, and heat generation decreases as the resistance value decreases. Therefore, according to the discharge resistance R ′, heat generation can be made variable according to the temperature of the arrangement region, and an excessive temperature rise can be suppressed.

The block diagram which showed the circuit example of the power converter device. The figure explaining arrangement | positioning of the smoothing capacitor and discharge resistance in a capacitor | condenser container. The external view of the power converter device shown about the assembly example of a capacitor | condenser container.

Explanation of symbols

C Smoothing capacitor C1 Capacitor element P, N Bus bar R, R 'Discharge resistance 2 Capacitor container

Claims (3)

A boost converter that boosts the power supply voltage;
An inverter that converts the DC power boosted by the boost converter into AC power;
A smoothing capacitor connected to a power supply line from the boost converter to the inverter;
A discharge resistor connected in parallel with the smoothing capacitor to the power supply line;
Comprising
The smoothing capacitor is configured as a module in which a plurality of capacitor elements are connected in parallel between a high potential side bus bar and a low potential side bus bar connected to the power supply line, and is stored in a capacitor container.
The discharge resistance is housed in a relatively low temperature portion of the capacitor container.   The power converter according to claim 1, wherein the discharge resistor is disposed in a region of the capacitor container opposite to the power source side of the bus bar.   The power converter according to claim 1, wherein the discharge resistor is an NTC thermistor.

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