JP2013198267A - Power conversion device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an interleave power conversion device having a plurality of step-up chopper circuits and capable of withstanding a rush current that possibly occurs at power on or restoration from blackout, without a large cost increase.SOLUTION: An interleave power conversion device includes reactors 3a-3d, switching elements 4a-4d and diodes 5a-5d, with a plurality of step-up chopper circuits 9a-9d in parallel connection to raise a voltage by chopping the output of a rectifier circuit 2 for rectifying AC power 1. The interleave power conversion device further includes a second diode 8 that bypasses the plurality of step-up chopper circuits 9a-9d in parallel connection, so that the rush current that occurs at power on or restoration from blackout is made to flow in an integrated manner.

Description

  The present invention relates to a power conversion device.

  Conventionally, as means for reducing the size and increasing the efficiency of a power conversion device that converts an AC power source into an arbitrary DC power source, a plurality of step-up chopper circuits including a reactor, a switching element, and a diode are connected in parallel. 2. Description of the Related Art A so-called interleaved power conversion circuit is known in which the conduction timing of each switching element is different from each other. As a technique applicable to this interleaved power conversion device, for example, as a reactor constituting a boost chopper circuit, a swing choke in which an inductance value does not change is adopted in a region where a flowing current is a certain value or more, and the reactor flows. A technique for maintaining high efficiency even when the current exceeds the current during maximum operation is disclosed (for example, Patent Document 1).

Japanese Patent No. 4771017

  In recent years, in order to further increase the efficiency of power conversion devices, silicon carbide (SiC), gallium nitride (GaN) based materials, or wide band gap (hereinafter referred to as “WBG”) semiconductors such as diamond have been formed. Examples of using switching elements and diodes are increasing. On the other hand, an interleaved power converter circuit consists of a plurality of boost chopper circuits connected in parallel, so that inrush current generated when power is turned on or when power is restored from a power failure due to variations in each element constituting each boost chopper circuit May not flow evenly in each boost chopper circuit, and there is a risk that inrush current flows in one boost chopper circuit. For this reason, all the diodes that make up each boost chopper circuit are made to have a large withstand capacity against overcurrent, more specifically, the maximum inrush current that can occur when power is turned on or when power is restored from a power failure. It is necessary to use a diode with a large chip size that can withstand. For this reason, when using a high-speed diode or a WBG diode formed of the above-described WBG semiconductor element, which has a relatively small withstand capability against overcurrent, the chip size becomes larger, leading to a reduction in cost. It becomes an obstacle. In particular, when an expensive WBG diode is used, increasing the chip size causes a large cost increase.

  The present invention has been made in view of the above, and in an interleaved power converter having a plurality of step-up chopper circuits, at the time of power-on or power recovery from a power failure without incurring a significant increase in cost. It aims at providing the power converter device which can endure the inrush current which may generate | occur | produce.

  In order to solve the above-described problems and achieve the object, a power converter according to the present invention includes a reactor, a switching element, and a first diode, and chops the output of a rectifier circuit that rectifies an AC power supply. An interleaved power converter configured by connecting a plurality of boosting chopper circuits that are boosted in parallel, comprising a second diode that bypasses the boosting chopper circuits connected in parallel. To do.

  According to the present invention, in an interleaved power conversion device having a plurality of step-up chopper circuits, power that can withstand an inrush current that can occur when power is turned on or when power is restored from a power failure without causing a significant increase in cost. There is an effect that a conversion device can be obtained.

FIG. 1 is a diagram illustrating a configuration example of the power conversion device according to the embodiment.

  Hereinafter, a power converter according to an embodiment of the present invention will be described with reference to the accompanying drawings. In addition, this invention is not limited by embodiment shown below.

Embodiment.
FIG. 1 is a diagram illustrating a configuration example of the power conversion device according to the embodiment. As shown in FIG. 1, the power converter according to the embodiment includes a single-phase rectifier circuit (hereinafter simply “rectifier circuit”) that rectifies an AC voltage of a single-phase AC power source (hereinafter simply referred to as “AC power source”) 1. 2), a step-up chopper circuit unit 9 and a smoothing capacitor 6 that smoothes the output of the step-up chopper circuit unit 9, and is configured to supply the DC power source boosted by the step-up chopper circuit unit 9 to the DC load 7. Yes.

  The rectifier circuit 2 is configured by bridge-connecting four rectifier diodes 2a to 2d. In the example shown in FIG. 1, the step-up chopper circuit unit 9 includes a step-up chopper circuit 9a including a reactor 3a, a switching element 4a, and a first diode 5a, and a reactor 3b, a switching element 4b, and a first diode 5b. A step-up chopper circuit 9b, a step-up chopper circuit 9c composed of a reactor 3c, a switching element 4c and a first diode 5c, and a step-up chopper circuit 9d composed of a reactor 3d, a switching element 4d and a first diode 5d are arranged in parallel. An example of connection is shown.

  In the present embodiment, the inrush current that flows through each of the first diodes 5a to 5d constituting the boost chopper circuits 9a to 9d of the boost chopper circuit unit 9 when the power is turned on or when power is restored from an instantaneous power failure. Is provided with a second diode 8 that bypasses the step-up chopper circuit unit 9. The inrush current suppressing operation to each of the first diodes 5a to 5d by the second diode 8 will be described later.

  Each of the first diodes 5a to 5d is, for example, a WBG formed of a fast recovery diode, a silicon carbide (SiC), a gallium nitride (GaN) -based material, or a wide band gap (hereinafter referred to as “WBG”) semiconductor such as diamond. It is assumed that the second diode 8 is composed of a diode, and is a Si diode composed of a Si-based semiconductor having a higher overcurrent tolerance than the first diodes 5a to 5d.

  In the example shown in FIG. 1, the AC power source 1 is a single-phase AC power source and the rectifier circuit 2 is configured as a single-phase rectifier circuit. However, the AC power source 1 is a three-phase AC power source and the rectifier circuit. 2 may be configured as a three-phase rectifier circuit. In the example shown in FIG. 1, an example in which two chopper circuit units are connected in parallel is shown. However, three or more chopper circuit units may be connected in parallel.

  In the example shown in FIG. 1, the boost chopper circuit unit 9 is configured by the four boost chopper circuits 9a to 9d. However, the boost chopper circuit unit 9 includes two, three, or more than five boost chopper circuits. It may be configured.

  Next, an inrush current suppression operation to each of the first diodes 5a to 5d by the second diode 8 in the power conversion device according to the present embodiment will be described.

  Before the AC power supply 1 is turned on or at the time of a power failure of the AC power supply 1, the smoothing capacitor 6 is almost not charged. Immediately after the AC power supply 1 is turned on or immediately after the AC power supply 1 recovers from a power failure while the smoothing capacitor 6 is hardly charged, the voltage across the terminals of the smoothing capacitor 6 becomes the peak voltage of the AC power supply 1. A large inrush current flows from the rectifier circuit 2 toward the smoothing capacitor 6 as much as possible. This inrush current is divided into four paths that flow through the reactors 3a to 3d and the first diodes 5a to 5d of the boost chopper circuits 9a to 9d and a path that flows through the second diode 8. To do.

  Here, in the conventional configuration that does not include the second diode 8, one path is provided due to variations in inductance values of the reactors 3a to 3d, variations in on-resistance values of the first diodes 5a to 5d, and the like. Inrush current may flow in a concentrated manner. For this reason, in the conventional configuration that does not include the second diode 8, all the first diodes 5a to 5d constituting the boost chopper circuits 9a to 9d are connected to each other when the power is turned on or when power is restored from a power failure. Therefore, it is necessary to use a diode having a large chip size that can withstand the maximum value of the inrush current that can be generated in the diode. For this reason, when a fast recovery diode or a WBG diode that has a relatively small tolerance to overcurrent is used as each of the first diodes 5a to 5d, the chip size is further increased, so that the cost is low. It becomes a hindrance to conversion. In particular, when an expensive WBG diode is used, increasing the chip size causes a large cost increase.

  On the other hand, in the configuration of the present embodiment including the second diode 8, each path on the boost chopper circuit unit 9 side including the first diodes 5a to 5d includes the reactors 3a to 3d. While the inductance by each of the reactors 3a to 3d becomes an element that prevents the inrush current, the path that flows through the second diode 8 has no element that prevents the inrush current. For this reason, most of the inrush current that can occur when power is turned on or when power is restored from a power failure flows into the smoothing capacitor 6 via the second diode 8, and the first diodes 5a to 5d are caused to flow through the first diodes 5a to 5d. Inrush currents flowing through the respective paths on the side of the step-up chopper circuit portion 9 can be suppressed.

  Therefore, in the power converter according to the present embodiment, the overcurrent withstand capability of each of the first diodes 5a to 5d constituting the boosting chopper circuit unit 9 is greatly increased as compared with the conventional configuration in which the second diode 8 is not provided. Therefore, it is possible to reduce the chip size of each of the expensive first diodes 5a to 5d constituted by the fast recovery diode or the WBG diode, and it is possible to significantly reduce the cost. On the other hand, as the second diode 8, it is only necessary to bypass the inrush current that can occur when the power is turned on or when power is restored from a power failure, and it is sufficient to ensure an overcurrent withstand capability that can withstand this inrush current. There is no need for an expensive fast recovery diode, WBG diode, or the like, and a cheaper and lower speed Si diode may be used.

  Further, as each of the first diodes 5a to 5d constituting the step-up chopper circuit unit 9, a WBG diode whose forward voltage increases as the temperature increases is used, and as the second diode 8, the forward voltage increases as the temperature increases. When a smaller Si diode is used, an inrush current is less likely to flow through each path on the step-up chopper circuit portion 9 side as the temperature rises due to heat generation during operation of the device, and more into the path flowing through the second diode 8. Since the inrush current easily flows, the effect of suppressing the inrush current to each of the first diodes 5a to 5d constituting the boost chopper circuit unit 9 is further increased.

  As described above, according to the power conversion device of the embodiment, in the interleaved power conversion device having a plurality of boost chopper circuits, the second bypassing the boost chopper circuit unit configured by the plurality of boost chopper circuits. Since the second diode 8 can bypass most of the inrush current that occurs when the power is turned on or when power is restored after a power failure, each diode constituting each boost chopper circuit is provided. The overcurrent immunity of the first diode can be greatly suppressed, the chip size of each expensive first diode composed of a fast recovery diode or a WBG diode can be reduced, and the cost can be significantly reduced. It becomes.

  On the other hand, as the second diode, it is only necessary to secure an overcurrent withstand capability that can withstand an inrush current that can occur when the power is turned on or when power is restored from a power failure. Can do.

  As described above, according to the power conversion device of the embodiment, in the interleaved power conversion device having a plurality of boosting chopper circuits, power is turned on or when power is restored from an instantaneous power failure without causing a large cost increase. It is possible to obtain a power conversion device that can withstand an inrush current that can occur in

  In addition, according to the power conversion device of the embodiment, even when the number of boost chopper circuits connected in parallel increases, the second diode is uniquely provided, so that each boost diode circuit constituting each boost chopper circuit can be connected to each first diode. An inrush current suppression effect can be obtained, and an inrush current suppression effect with higher cost performance can be obtained as the number of boost chopper circuits connected in parallel increases.

  In the above-described embodiment, the example in which the first diodes constituting the boost chopper circuit are formed of the WBG semiconductor has been described. However, the switching elements constituting the boost chopper circuit are formed of the WBG semiconductor. May be.

  A WBG semiconductor has small switching loss and conduction loss as compared with a Si-based semiconductor, has high heat resistance, and can operate at a high temperature. Therefore, not only each first diode constituting the boost chopper circuit but also each switching element constituting the boost chopper circuit is formed of a WBG semiconductor, and each of these switching elements is formed of a Si-based semiconductor. In addition, the heat radiation design can be further simplified, for example, by reducing the size of the heat sink.

  Furthermore, since the switching element and the diode formed of such a WBG semiconductor have high voltage resistance and high allowable current density, the switching element and the diode itself can be downsized.

  Therefore, by using a switching element and a diode formed of a WBG semiconductor as each switching element and each first diode constituting the boost chopper circuit, it is possible to reduce the size and cost of the power converter. .

  Note that the configuration shown in the above embodiment is an example of the configuration of the present invention, and can be combined with another known technique, and a part thereof is omitted without departing from the gist of the present invention. Needless to say, it is possible to change the configuration.

1 AC power supply 2 Single-phase rectifier circuit (rectifier circuit)
2a to 2d Rectifier diode 3a to 3d Reactor 4a to 4d Switching element 5a to 5d First diode 6 Smoothing capacitor 7 DC load 8 Second diode 9 Boost chopper circuit section 9a to 9d Boost chopper circuit

Claims (5)

Interleaved power conversion configured with a reactor, a switching element, and a first diode, and connected in parallel with a plurality of boost chopper circuits that chop and boost the output of a rectifier circuit that rectifies an AC power supply A device,
A power conversion device comprising: a second diode having a larger overcurrent tolerance than each of the first diodes and bypassing the step-up chopper circuits connected in parallel.   The power converter according to claim 1, wherein each of the first diodes is a fast recovery diode.   The power converter according to claim 1, wherein each first diode is formed of a wide band gap semiconductor.   4. The power conversion device according to claim 1, wherein each of the switching elements is formed of a wide band gap semiconductor.   The power converter according to claim 3 or 4, wherein the wide band gap semiconductor is silicon carbide, a gallium nitride-based material, or diamond.

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