JP6525916B2 - Power converter - Google Patents

Description

  The present invention relates to a power converter.

  Generally, it is known to connect a plurality of unit capacitors of small capacity in series and in parallel to use as a smoothing capacitor of an inverter. Moreover, in order to prevent explosion of a capacitor, providing a fuse is disclosed (refer to patent documents 1).

Unexamined-Japanese-Patent No. 5-207746

  However, when all unit capacitors are disconnected by one fuse, the interrupting capacity of the fuse is determined with respect to the total capacitance of all unit capacitors, so the interrupting capacity of the fuse is increased. In this case, the fault current (short circuit current) flowing before the fuse is blown increases, and the fault current flowing before the fuse causes the other circuit to propagate the fault, and in some cases, the parts constituting the power conversion device rupture. there is a possibility.

  Then, the objective of this invention is providing the power converter device which provided the fuse so that the fault current which flows from the DC capacitor comprised with several unit capacitors may be suppressed.

The power converter according to the aspect of the present invention is provided so as to separate a plurality of unit capacitors constituting one DC capacitor and a part of unit capacitors among the plurality of unit capacitors from the configuration of the DC capacitor. The power conversion circuit includes at least one fuse, and a switching element for passing a current from the DC capacitor or supplying a current to the DC capacitor . The plurality of capacitors are connected in parallel, and the DC capacitor is a fault current based on the capacitance of the DC capacitor flowing before the partial capacitor is disconnected by the at least one fuse until the partial capacitance is disconnected. anti爆耐amount of switching elements Ru is configured to be less than.

  According to the present invention, it is possible to provide a power conversion device provided with a fuse such that a fault current flowing from a DC capacitor constituted of a plurality of unit capacitors is suppressed.

BRIEF DESCRIPTION OF THE DRAWINGS The block diagram which shows the structure of the power converter device which concerns on the 1st Embodiment of this invention. The block diagram which shows the structure of the power converter device which concerns on the 2nd Embodiment of this invention.

First Embodiment
FIG. 1: is a block diagram which shows the structure of the power converter device 1 which concerns on the 1st Embodiment of this invention. The same reference numerals are given to the same parts in the drawings, and duplicate explanations are omitted.

  The power conversion device 1 supplies DC power to the load 5 based on single-phase AC power supplied from the AC power supply 4.

  The power conversion device 1 includes a power conversion circuit 2 and a DC capacitor 3.

  The power conversion circuit 2 includes four switching elements (power semiconductors) 21a, 21b, 21c, 21d and four antiparallel diodes 22a, 22b, 22c, 22d. The antiparallel diodes 22a to 22d are connected in antiparallel to the switching elements 21a to 21d, respectively. An alternating current power supply 4 is connected to the alternating current side of the power conversion circuit 2. The load 5 is connected to the DC side of the power conversion circuit 2 by the positive electrode wiring LP and the negative electrode wiring LN.

  For example, the four switching elements (power semiconductors) 21a to 21d and the four anti-parallel diodes 22a to 22d may be pressure-welded semiconductor elements whose outer shapes are covered with a ceramic, and the outer shapes may be covered with plastic or the like. It may be a modular type or any other type.

  The two switching elements 21a and 21b are connected in series. The switching elements 21a and 21b connected in series are connected between the positive electrode wiring LP of direct current and the negative electrode wiring LN. Thus, one arm of the power conversion circuit 2 is configured. The other two switching elements 21c and 21d are connected in series. The switching elements 21c and 21d connected in series are connected between the positive electrode wiring LP of direct current and the negative electrode wiring LN. Thus, another arm of the power conversion circuit 2 is configured. The single-phase AC power from the AC power supply 4 is input between the connection points of the switching elements 21 a to 21 d connected in series in two sets.

  The DC capacitor 3 is composed of a plurality of unit capacitors 31 a, 31 b, 31 c, 31 d, 31 e, a fuse 32 and a damping resistor 33. The plurality of unit capacitors 31a to 31e are connected in parallel. As a result, the capacitance of the DC capacitor 3 (the sum of the capacitances of all the unit capacitors 31a to 31e) is increased. The DC capacitor 3 is a smoothing capacitor that smoothes the DC voltage converted by the power conversion circuit 2. Here, although the DC capacitor 3 is described as being configured of five unit capacitors 31a to 31e, as long as it is two or more, any number of unit capacitors may be used. Further, the direct current capacitor 3 is not limited to one in which all unit capacitors are connected in parallel, and some unit capacitors may be connected in series.

  Five unit capacitors 31a to 31e are in two groups G1 and G2 of a first group G1 including three unit capacitors 31a, 31b and 31c and a second group G2 including two unit capacitors 31d and 31e. It is divided. The first group G1 is a group electrically distant from the switching elements 21a to 21d. The second group G2 is a group electrically close to the switching elements 21a to 21d. The grouping may be divided on any basis or in any number.

  As for the capacitor capacity of the second group G2 (the capacitor capacity of the sum of the unit capacitors 31d and 31e included in the second group G2), the short circuit current (accident current) flowing at the time of the short circuit of the switching elements 21a It is set to a current (explosion proof capacity) or less that does not rupture even if it flows to 21 d. Here, the short circuit current is obtained from the capacitance of the DC capacitor 3. Therefore, the capacitor capacity of the first group G1 to be separated (the capacitor capacity of the sum of the unit capacitors 31a to 31c included in the first group G1) is the capacity of the DC capacitor 3 among the capacitor capacities of the switching elements 21a to 21d. Make the capacitance more than the excess capacity.

  The fuse 32 and the damping resistor 33 are connected in series. The fuse 32 and the damping resistor 33 connected in series are connected so as to be inserted into a positive electrode wire (which may be a negative electrode wire) connecting the two groups G1 and G2. It should be noted that when the fuse 32 is melted, some (for example, group G1) unit capacitors 31a to 31c are disconnected from the circuit constituting the DC capacitor 3, and if the capacitor capacity of the DC capacitor 3 decreases, Thus, the fuse 32 may be provided. Also, any number of fuses 32 may be provided at the same place on the electric circuit. In this case, no matter how many fuses 32 are provided at the same place on the electric circuit, it is the same as being provided at one place. Details of the division of the two groups G1 and G2 will be described later.

  The fuse 32 is fused when the short circuit current flowing through the fuse 32 becomes a current higher than the fusing characteristic curve of the fuse. When the fuse 32 is melted, the unit capacitors 31a to 31c of the first group G1 are disconnected from the configuration of the DC capacitor 3 and do not form a closed circuit with the switching elements 21a to 21d. Therefore, if the fuse 32 is melted, the fault current from the unit capacitors 31a to 31c of the first group G1 does not flow into the circuit in which the switching elements 21a to 21d exist. The damping resistor 33 is provided to suppress the resonance current due to the inductance increased by the insertion of the fuse 32 and the capacitance of the DC capacitor 3. The damping resistor 33 may be provided anywhere as long as it is provided to suppress the resonance current, and may be provided any number. Further, it is desirable that the damping resistor 33 is not provided unless the resonance current needs to be suppressed.

  Next, a mechanism for suppressing the short circuit current when the switching elements 21a to 21d are shorted will be described.

  When one of the switching elements 21a to 21d is shorted, a short circuit current flows in a closed circuit formed by the DC capacitor 3 and the switching elements 21a to 21d.

  When a short circuit current flows from the unit capacitors 31a to 31c of the first group G1 to the fuse 32, the fuse 32 is melted. When the fuse 32 is melted, the unit capacitors 31 a to 31 c of the first group G 1 are disconnected from the configuration of the DC capacitor 3. As a result, the capacity of the DC capacitor 3 is reduced by the capacity of the first group G1. Therefore, the short circuit current is reduced by an amount corresponding to the capacitor capacity of the first group G1.

  Here, the current squared time product of the current flowing from the unit capacitors 31a to 31c of the first group G1 to the switching elements 21a to 21d until the fuse 32 is melted and the unit capacitors 31d and 31e of the second group G2 The fusing characteristics of the fuse 32 are selected such that the sum of the current flowing through the switching elements 21a to 21d and the current squared time product of the currents is equal to or less than the explosion proof resistance of the switching elements 21a to 21d. In addition to this, the DC capacitor 3 divides the group G1 separated by the fuse 32 into two groups G1 and G2 of the group G2 not separated. As a result, the failure current based on the capacitance of the DC capacitor 3 which flows before the unit capacitors 31a to 31c of the first group G1 are disconnected by the fuse 32 becomes equal to or less than the explosion proof resistance of the switching elements 21a to 21d. Then, the direct current capacitor 3 is configured.

  According to the present embodiment, the fuse 32 is provided in the circuit constituting the DC capacitor 3 and the fuse 32 is melted by the fault current, whereby part of the unit capacitors 31 a to 31 c constituting the DC capacitor 3 can be disconnected. . As a result, the capacity of the DC capacitor 3 is substantially reduced, so that the failure current can be suppressed. Therefore, it is possible to prevent the switching elements 21a to 21d from being ruptured by the fault current flowing from the DC capacitor 3. Since excessive fault current is suppressed, it is possible to prevent mechanical deformation or failure of parts or conductors due to electromagnetic force or the like.

  Further, the suppression of the fault current suppresses the explosion of the DC capacitor 3 and the like caused by the fault current. On the other hand, when the fuses are provided so that all the unit capacitors 31a to 31e that constitute the DC capacitor 3 are disconnected, a fuse of a blocking capacity corresponding to the total capacitance of all the unit capacitors 31a to 31e is provided. Furthermore, all the ripple current flowing to the DC capacitor 3 during the normal operation flows through the fuse. In this case, in order to always coordinate with the current, the fuse has a large fault current flowing until it blows. For this reason, there is a possibility that the switching elements 21a to 21d may be ruptured by the fault current which has flowed until the fuse is blown. On the other hand, in the present embodiment, since the fuse 32 is provided to disconnect some of the unit capacitors 31a to 31c, the fusing current of the fuse 32 is reduced and the fuse 32 is fused by a small fusing current. The peak value of the short circuit current flowing to 21a to 21d can be reduced.

  Further, since the fuses 32 may be provided in group units to be separated, DCs can be generated by a smaller number (one in the present embodiment) of the fuses 32 compared to the case where the fuses are individually provided for all unit capacitors 31a to 31e. The fault current flowing from the capacitor 3 can be suppressed.

Second Embodiment
FIG. 2 is a configuration diagram showing a configuration of a power conversion device 1A according to a second embodiment of the present invention.

  The power conversion device 1A is obtained by replacing the direct current capacitor 3 with a direct current capacitor 3A in the power conversion device 1 according to the first embodiment shown in FIG. The other points are the same as in the first embodiment.

  In the direct current capacitor 3A, in the direct current capacitor 3 according to the first embodiment shown in FIG. 1, three fuses 32a, 32b and 32c are provided instead of the fuse 32 and three damping resistors 33a and 33b instead of the damping resistor 33. , 33c are provided. The other points are the same as the direct current capacitor 3 according to the first embodiment.

  Here, although the configuration in which the fuses 32a to 32c correspond to the unit capacitors 31a to 31c on a one-to-one basis will be described, the present invention is not limited to this. Only one fuse may be provided for a plurality of unit capacitors. When there are unit capacitors connected in series, only one fuse may be provided on the wiring provided with the unit capacitors connected in series. Therefore, the number of fuses may be equal to or less than the number of paralleled unit capacitors to be disconnected in parallel. That is, when the fuses 32a to 32c are fused, some of the unit capacitors 31a to 31c are disconnected from the configuration of the DC capacitor 3A, and if the capacitor capacity of the DC capacitor 3A decreases, the fuse is provided anywhere May be

  The damping resistors 33a to 33c are connected in series to the fuses 32a to 32c, respectively. The fuses 32a to 32c and the damping resistors 33a to 33c connected in series are connected in series to the unit capacitors 31a to 31c, respectively. The fuses 32 a to 32 c and the damping resistors 33 a to 33 c are the same as the fuse 32 and the damping resistor 33 according to the first embodiment in the other points. The damping resistors 33a to 33c may not be provided corresponding to the fuses 32a to 32c, and may not be provided as in the first embodiment.

  The unit capacitors 31a to 31c to which the fuses 32a to 32c are connected correspond to the unit capacitors 31a to 31c included in the first group G1 in the first embodiment, and the unit capacitors 31d and 31e to which the fuses are not connected This corresponds to the unit capacitors 31d and 31e included in the second group G2 in the first embodiment.

  In such a configuration, when any of the switching elements 21a to 21d is short-circuited, the fuses 32a to 32c are melted down by the short circuit current from the unit capacitors 31a to 31c connected in series. When all the fuses 32a-32c are fused, the three unit capacitors 31a-31c are disconnected from the circuit constituting the DC capacitor 3A. As a result, in the first embodiment, the state is the same as when the fuse 32 is melted.

  That is, in a state where all the fuses 32a to 32c are fused, the substantial capacitance of the DC capacitor 3A is the sum of capacitances of the unit capacitors 31d and 31e to which the fuses 32a to 32c are not connected. The capacitor capacity of the sum of the unit capacitors 31d and 31e which are not separated is provided so that the short circuit current is equal to or less than the explosion proof withstand voltage of the switching elements 21a to 21d as in the first embodiment. Therefore, the switching elements 21a to 21d can be prevented from bursting. In addition, since excessive fault current is suppressed, it is possible to prevent mechanical deformation or failure of parts or conductors due to electromagnetic force or the like.

  According to the present embodiment, in addition to the first action and effect, the following action and effect can be obtained.

  By providing the fuses 32a to 32c and the damping resistors 33a to 33c individually to some unit capacitors 31a to 31c, the capacities of the individual fuses 32a to 32c and the damping resistors 33a to 33c can be reduced according to the first embodiment. 32 and the damping resistance 33 can be made smaller. Therefore, the power converter 1A can be miniaturized or reduced in cost more than the power converter 1 according to the first embodiment by selecting or arranging the plurality of fuses 32a to 32c and the damping resistors 33a to 33c. it can.

  In each embodiment, although explained as power conversion device 1 and 1A which converts single phase alternating current electric power into direct current electric power, it does not restrict to this. Any power converter may be used as long as it is a power conversion device using the DC capacitors 3 and 3A composed of a plurality of unit capacitors 31a to 31e. For example, a converter that converts AC power other than single phase (for example, three phases) to DC power may be used, an inverter that converts DC power to AC power may be used, or an inverter may be provided as the load 5. -back) may be used as a converter. Power converters 1 and 1A may be used for any application. For example, power may be supplied directly to an AC load or DC load, or may be used for DC power transmission.

  The present invention is not limited to the above embodiment as it is, and at the implementation stage, the constituent elements can be modified and embodied without departing from the scope of the invention. In addition, various inventions can be formed by appropriate combinations of a plurality of components disclosed in the above embodiments. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, components in different embodiments may be combined as appropriate.

  DESCRIPTION OF SYMBOLS 1 ... Power conversion device, 2 ... Power conversion circuit, 3 ... DC capacitor, 4 ... AC power supply, 5 ... Load, 21a-21d ... Switching element, 22a-22d ... Reverse parallel diode, 31a-31e ... Unit capacitor, 32 ... Fuse, 33 ... dumping resistance.

Claims (5)

A plurality of unit capacitors constituting one DC capacitor,
At least one fuse provided to disconnect some of the unit capacitors of the plurality of unit capacitors from the configuration of the DC capacitor ;
A power conversion circuit including a switching element for passing a current from the DC capacitor or supplying a current to the DC capacitor ;
The plurality of unit capacitors are connected in parallel,
The DC capacitor is configured such that a failure current based on the capacitance of the DC capacitor flowing before the partial capacitor is disconnected by the at least one fuse is equal to or less than the explosion proof resistance of the switching element. by power converter according to claim Rukoto. The power conversion device according to claim 1, further comprising a damping resistor that suppresses a resonance current generated by the fuse. The fuse, the power conversion apparatus according to claim 1 or 2, characterized in that provided in one location on an electric circuit. The fuse, the power conversion apparatus according to claim 1 or 2, wherein the portion of the unit capacitor is less than the number of parallel connected in parallel. A plurality of unit capacitors constituting one DC capacitor, at least one fuse provided so as to disconnect a part of unit capacitors among the plurality of unit capacitors from the configuration of the DC capacitor, a current from the DC capacitor sink, or the saw including a power conversion circuit including switching elements for supplying current to the DC capacitor, said plurality of unit capacitors, a connected protection method of the power converter in parallel,
Fusing the fuse with a fault current that has flowed due to a fault of the power conversion circuit,
Disconnecting some of the unit capacitors by blowing the fuse,
The capacitor capacity of the DC capacitor is reduced to suppress the fault current supplied to the switching element,
The method for protecting a power conversion device according to claim 1, wherein suppressing the failure current includes that a failure current based on the capacitor capacity is equal to or less than an explosion proof resistance of the switching element .

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