Power converter

Abstract

The present application provides a power converter that suppresses occurrence of secondary element damage of a normal inverter unit by suppressing a rise in DC voltage by rapidly fusing a DC fuse when an element is damaged. A power converter (1) includes a plurality of inverter units (30) connected in parallel to a DC power supply (10) composed of a storage battery on a DC side, and a DC fuse (6) provided in a circuit between the DC power supply and the plurality of inverter units, and fused in a circuit between the DC power supply and an inverter unit in which a short-circuit failure has occurred when the short-circuit failure has occurred in the inverter unit. The number of the plurality of inverter units is a number that satisfies a condition that when the DC fuse between the DC power supply and the inverter unit in which the short-circuit failure has occurred is fused, none of the plurality of DC fuses between the DC power supply and other inverter units in which the short-circuit failure has not occurred is fused.

Description

TECHNICAL FIELD

[0001] The present application relates to a power converter. BACKGROUND

[0002] Conventionally, in order to realize a large capacity of a power converter, a power converter in which a plurality of inverter units that convert direct current power into alternating current power are connected in parallel is known. Also, in realizing a large capacity power converter in which a plurality of inverter units are connected in parallel, conventionally, the capacity of each inverter unit is made large, and the number of inverter units is made as small as possible, and labor saving in wiring work and the like is realized.

[0003] In such a power converter, a protection method in which a direct current fuse is provided in order to break a current in the case where a short circuit failure such as a component failure occurs in the components within the plurality of inverter units connected in parallel is known (for example, refer to Patent Document 1).

[0004] PRIOR ART DOCUMENTS

[0005] PATENT DOCUMENT

[0006] Patent Document 1: Japanese Patent Application Publication No. 2007-074823 SUMMARY

[0007] PROBLEMS TO BE SOLVED BY THE INVENTION

[0008] However, if the capacity of the direct current fuse is too large, even if the fusing of the direct current fuse is performed, the time of the fusing becomes slow, and the rise of the direct current link voltage (a direct current voltage input to the inverter) will become large. If the rise of the direct current link voltage greatly exceeds the withstand voltage of the components, a secondary component failure occurs in the normal inverter unit as well.

[0009] Therefore, an object of the present application is to provide a power converter that suppresses the occurrence of a secondary component failure of a normal inverter unit by rapidly fusing a direct current fuse at the time of a component failure and suppressing the rise of a direct current link voltage.

[0010] MEANS FOR SOLVING THE PROBLEMS

[0011] A power converter according to a technical solution of the present invention comprises: a plurality of inverter units connected in parallel on the DC side to a DC power supply consisting of a battery, each having a plurality of semiconductor elements; and DC fuses respectively disposed in the circuit between the DC power supply and the plurality of inverter units, wherein when a short-circuit fault occurs in one of the plurality of inverter units, the fuses are melted in the circuit between the DC power supply and the inverter unit that has experienced a short-circuit fault; the number of the plurality of inverter units is such that when the DC fuse between the DC power supply and the inverter unit that has experienced a short-circuit fault is melted, the plurality of DC fuses between the DC power supply and the other plurality of inverter units that have not experienced a short-circuit fault are not melted.

[0012] In a power converter of a certain technical solution, the number of multiple inverter units can also be greater than the number of multiple semiconductor elements.

[0013] In a power converter of a certain technical solution, the number of multiple inverter units can also be greater than 4.

[0014] Invention Effects

[0015] According to the present invention, a power converter can be provided that suppresses the rise of DC link voltage by rapidly blowing the DC fuse when a component fails, thereby suppressing the occurrence of secondary component failure in the normal inverter unit. Attached Figure Description

[0016] Figure 1 This is a diagram illustrating an example of the configuration of a power converter according to one embodiment.

[0017] Figure 2 This diagram illustrates an example of DC circuit protection using a DC circuit breaker.

[0018] Figure 3 This diagram illustrates an example of DC circuit protection using a DC fuse.

[0019] Figure 4 This diagram illustrates an example of the increasing capacity of power converters.

[0020] Figure 5 It means Figure 4 The diagram shows an example of the operation of a large-capacity power converter during a fault.

[0021] Figure 6 This is a diagram showing an example of the parallel connection of inverter units and semiconductor elements.

[0022] Figure 7 This is a diagram showing an example of the rated value of a DC fuse.

[0023] Figure 8is a diagram showing a configuration example of a conventional power converter relating to a comparative example and a configuration example of a power converter relating to an embodiment.

[0024] Figure 9 is a diagram showing a configuration example of a conventional power converter relating to a comparative example and a configuration example of a power converter relating to an embodiment. Figure 8 is a diagram showing a configuration example of a conventional power converter relating to a comparative example and a configuration example of a power converter relating to an embodiment. DETAILED DESCRIPTION

[0025] Hereinafter, an embodiment of a power converter relating to the present application will be described using the drawings.

[0026] <Embodiment>

[0027] Figure 1 is a diagram showing a configuration example of a power converter 1 relating to an embodiment. Figure 1 (a) of FIG. 1 is a diagram showing a configuration example of a two-level power converter 1A, Figure 1 (b) of FIG. 1 is a diagram showing a configuration example of a neutral-point-switched three-level power converter 1B, Figure 1 (c) of FIG. 1 is a diagram showing a configuration example of a neutral-point-clamped three-level power converter 1C.

[0028] For example, Figure 1 The two-level power converter 1A in (a) of FIG. 1 has a positive electrode P and a negative electrode N on the direct-current side. Figure 1 The neutral-point-switched three-level power converter 1B in (b) of FIG. 1 and Figure 1 The neutral-point-clamped three-level power converter 1C in (c) of FIG. 1 has a positive electrode P, a negative electrode N, and a neutral point C on the direct-current side. The positive electrode P, the negative electrode N, and the neutral point C are connected to a direct-current power supply 10 (see Figure 2 ) via a circuit (direct-current bus). In addition, the direct-current power supply 10 (see Figure 2 ) of the present embodiment is a storage battery. Therefore, hereinafter, the direct-current power supply 10 will also be referred to as a storage battery 10.

[0029] In addition, the present application can be applied to any one of the power converters 1A, 1B, 1C of the present embodiment. Hereinafter, in the present embodiment, the power converters 1A, 1B, 1C will be collectively referred to as a power converter 1 or an inverter 1. The power converter 1 is connected to an alternating-current system 20 via, for example, a harmonic filter or the like, which is not shown, from an alternating-current terminal.

[0030] If the power converter 1 of the present embodiment is used as an inverter 1, the inverter 1 is connected to the alternating-current system 20 via, for example, a harmonic filter or the like, which is not shown, from an alternating-current terminal. Figure 1The two-level power converter 1A in (a) is described as an example. The power converter 1 has arms 2, legs 3, and capacitors 4. The arms 2 represent individual elements in a bridge circuit. The legs 3 represent a set of upper and lower arms 2 connected in series between the positive and negative poles on the DC side. In addition, a single-phase full-bridge circuit is composed of 2 arms (1 leg) or 4 arms (2 legs), and a three-phase full-bridge circuit is composed of 6 arms (3 legs), but the number of phases is not limited in the present application. The power converter 1 flows a sinusoidal current on the AC side by alternately switching the upper and lower arms 2 in (a). Figure 1

[0031] The capacitors 4 absorb the ripple current occurring by alternately switching the upper and lower arms 2 because no burden is applied on the DC power source 10 side. In addition, Figure 1 The neutral-point switching three-level power converter 1B in (b) and Figure 1 The neutral-point clamped three-level power converter 1C in (c) also has the same configuration as the two-level power converter 1A in (a). Figure 1

[0032] Figure 2 is a diagram showing an example of DC circuit protection using a DC breaker. In Figure 2 , the power converter 1 has three-phase legs 3, is connected to a DC power source (battery) 10 on the DC side, and is connected to an AC system 20 on the AC side. In addition, the power converter 1 of the present embodiment is a voltage-type inverter.

[0033] Generally, in the power converter 1 as a voltage-type inverter, a control system is incorporated so that the upper arm 2 and the lower arm 2 are not simultaneously turned on. This is because, if the upper and lower arms 2 are simultaneously turned on, PN short-circuit (short-circuit of the positive side and the negative side) occurs, and there is a case where an element is damaged. However, there are cases where an element is damaged due to an accidental failure of a semiconductor or a malfunction due to noise, and the like. For example, if the upper arm 2 has a short-circuit failure when the arm 2 switch on the lower left in the diagram, PN short-circuit occurs. If this state is left as it is, an excessive current continues to flow from the DC power source 10 to the short-circuit point, and an excessive current also flows in the lower arm 2 that is normally switched on to cause a failure. If the failure is further left as it is, the current further flows in, and there is a risk that the failure spreads to other parts or causes a fire or smoke, and the like. Therefore, the power converter 1 needs protection of the DC circuit.

[0034] First, it is possible to consider, as Figure 2 ​​As shown, a DC circuit breaker 5 is installed between the battery 10 and the power converter 1 in the DC circuit. When a PN short circuit occurs, the DC circuit breaker 5 is used to disconnect the short circuit point from the battery 10. Furthermore, the DC circuit breaker 5 is a switching mechanism capable of interrupting fault current. According to the DC circuit breaker 5, by detecting the fault current of a short circuit fault and opening / closing the circuit (busbar), the short circuit point can be disconnected from the battery 10.

[0035] However, DC circuit breakers 5 with high voltage levels, such as 1500V and above, are very expensive, and even if they exist, they are very large. Therefore, protection mechanisms for DC circuits based on DC circuit breakers 5 can be used, for example, for voltage levels below 1000V, but for high voltage levels, such as 1500V and above, protection mechanisms for DC circuits based on DC circuit breakers 5 are generally not feasible. Therefore, in cases of high voltage levels, such as 1500V and above, a DC fuse 6 is installed in the DC circuit (see reference). Figure 3 And by using DC fuse 6 to disconnect the short circuit point from other normal circuits.

[0036] Figure 3 This diagram illustrates an example of DC circuit protection using a DC fuse. (See diagram for example.) Figure 3 As shown, when using DC fuses to protect DC circuits, DC fuses 6 are installed at the inlets on the positive P side and the negative N side. DC fuses 6 are typically selected with a current rating that has a specified margin, ensuring that they will not unnecessarily blow even when operating at rated current, and that they will reliably blow under fault current.

[0037] If such a DC fuse 6 is used, even if a short circuit fault occurs, for example, in the upper or lower arm 2, the DC fuse 6 will blow under the fault current, thus isolating the fault point from the battery 10. On the other hand, if such a DC fuse 6 is used, even when operating at the rated current, unnecessary blowing or malfunction will not occur. Therefore, for example, in high voltage situations of 1500V or higher, a method is adopted to install a DC fuse 6 in the DC circuit and isolate the short circuit point from other normal circuits through the DC fuse 6.

[0038] Figure 4 This diagram illustrates an example of increasing the capacity of power converter 1. In Figure 4 In this configuration, the three inverter units 30 of the power converter 1 are connected in parallel with the battery 10. For example... Figure 4In each of the inverter units 30, a plurality of semiconductor elements 40 are connected in parallel in each arm 2 (each leg 3) as shown in the lower part of FIG. 1. In addition, the reference numeral 7 denotes an internal impedance (e.g., an LR component) of the battery 10. Here, the reference of the large capacity is not a numerical reference, but refers to a capacity that cannot be achieved if a single semiconductor element 40 is not connected in parallel with a plurality of semiconductor elements 40.

[0039] In the case of the power converter 1 of a certain basic design, a power converter 1 of a larger capacity (i.e., capable of performing a larger power conversion than the basic design) is implemented. In this case, a method of achieving a larger capacity by increasing the voltage or increasing the current can be considered. However, as to the method of increasing the voltage, generally, a battery device is implemented by connecting a plurality of single cell units in series and in parallel, but this depends on the design of each battery manufacturer. That is, since several hundred volts, several thousand amperes of current do not flow through 1 cell, the method of increasing the voltage is almost always implemented by incorporating a smaller single cell unit of several volts, several amperes in 1 cell and connecting a plurality of them in series and in parallel. Furthermore, it is not possible to increase the voltage as much as desired because of problems such as the withstand voltage.

[0040] On the other hand, as to the method of increasing the current, it is sufficient to increase the number of parallel connections of the inverter, so a large capacity power converter 1 can be easily constructed compared to the method of increasing the voltage. In order to adopt this method, it is possible to consider connecting a plurality of the same power converter 1 in parallel or increasing the single capacity of the power converter 1. Furthermore, in order to increase the single capacity of the power converter 1, it is possible to consider a method of using a semiconductor element 40 having a larger current rating than the basic semiconductor element 40 or connecting a plurality of semiconductor elements 40 in parallel. However, the method of using a semiconductor element 40 having a larger current rating is limited, so the method of connecting a plurality of semiconductor elements 40 in parallel is adopted. That is, this method is a method of connecting a plurality of semiconductor elements 40 in parallel as 1 switch. However, if the semiconductor elements 40 are excessively increased, the cooling mechanism (fins, etc.) becomes large and the manufacturability and maintainability become poor.

[0041] Therefore, the semiconductor elements 40 are not able to be increased without limit. Thus, there is a case where a unit inverter unit 30 (unit unit 30) having a capacity larger than that of the usual inverter unit 30 is connected in parallel to the board. Furthermore, in the case of using a large capacity power converter 1 (also simply referred to as "large capacity power converter 1") of a larger capacity than the basic design power converter 1 by connecting a plurality of unit inverter units 30 in parallel, the protection of the direct current circuit is performed by the direct current fuse 6 as described above.

[0042] Figure 5 is a diagram showing Figure 4The diagram illustrates an example of the operation of a large-capacity power converter 1 during a fault. Figure 5 In the diagram, a short-circuit fault 8 of PN occurs in the topmost inverter unit 30. In the event of a short-circuit fault 8 in the topmost inverter unit 30, the currents flowing into the fault point are represented by (i), (ii), and (iii) in the diagram. (i) is the current flowing from the DC capacitor 4 of the inverter unit 30 where the short-circuit fault 8 occurred. (ii) is the current flowing from the DC capacitor 4 of the adjacent, normal inverter unit 30. (iii) is the current flowing from the battery 10.

[0043] like Figure 5 As shown, the current represented by (i) does not pass through the DC fuse 6 of the inverter unit 30 that has experienced a short-circuit fault 8, and therefore does not contribute to the blowing of the DC fuse 6. Furthermore, the current represented by (iii) rises more slowly than the currents in (i) and (ii) due to the influence of the wiring between the battery 10 and the power converter 1, and the internal impedance (LR component) 7 of the battery 10. Therefore, in a large-capacity power converter 1 where multiple inverter units are connected in parallel, the DC fuse 6 of the inverter unit 30 that has experienced a short-circuit fault is essentially blown by the current in (ii).

[0044] Figure 6 This diagram illustrates an example of the parallel connection of inverter unit 30 and semiconductor elements 40. For instance, in a power converter 1 where 15 to 16 semiconductor elements 40 need to be connected in parallel per phase to achieve a power converter 1 with a larger capacity than the basic design, such as... Figure 6 As shown, several styles can be adopted.

[0045] For example, from Figure 6 Starting from the left, there are, in sequence, a configuration of 16 semiconductor elements 40 connected in parallel as 2 elements in parallel (8 units), and a configuration of 15 semiconductor elements 40 connected in parallel as 3 elements in parallel (5 units). Additionally, there are configurations of 16 semiconductor elements 40 connected in parallel as 4 elements in parallel (4 units), and configurations of 15 semiconductor elements 40 connected in parallel as 5 elements in parallel (3 units). Furthermore, there is a configuration of 16 semiconductor elements 40 connected in parallel as 8 elements in parallel (2 units).

[0046] Among these patterns, there are advantages respectively. For example, in terms of the number of wirings, in the case where a signal (gate signal) to turn on / off the semiconductor element 40 is sent out from a control device not shown, if it is an 8-element parallel 2-unit configuration, that is, if the inverter unit 30 is only two, it is enough to make two wirings. On the other hand, in the case of a 2-element parallel 8-unit configuration, that is, in the case where the inverter unit 30 is eight, it is necessary to make eight wirings. That is, the more the number of inverter units 30 increases, the more the number of wirings increases. Further, the configuration in the disk is also that the more the division is fine, the more the metal plate inside increases, and the more the configuration is complicated.

[0047] On the other hand, if this point of maintainability is focused on, the inverter unit 30 of the 2-element parallel 8-unit configuration can realize a smaller and lighter unit than the inverter unit 30 of the 8-element parallel 2-unit configuration. Therefore, if this point of maintainability is focused on, the inverter unit 30 of the 2-element parallel 8-unit configuration is better.

[0048] Therefore, these patterns are as described above, and there is a trade-off relationship among several elements. In the past, the capacity of each unit inverter unit 30 was made larger, and the number of inverter units 30 was made as small as possible to realize the labor saving of wirings and the simplification of the configuration in the disk, and the like. However, in the present application, as will be described later, by focusing on the property of the direct current fuse 6, the capacity of each unit inverter unit 30 is actively made smaller, and the number of inverter units 30 is actively increased.

[0049] Figure 7 is a chart showing examples of the direct current fuse rating. In Figure 7 , the specifications of two fuses are listed. The leftmost is the fuse size, and both of the fuse sizes are 30. The column to the right is the rated current (current rating), and the upper fuse is 200 (A), and the lower fuse is 400 (A). Continuing to the right, next is the rated voltage (voltage rating), and both are 690 (V). One more to the right, the fourth column from the left is the fuse I 2 t. The fuse I 2 t of the fuse with the rated current of 200 (A) is 3 (A 2 s x 10 3 ), and the fuse I 2 t of the fuse with the rated current of 400 (A) is 23 (A 2 s x 10 3 ).

[0050] The fuse I 2 t is a barometer of the fuse blowing, and the larger the fuse I 2 t, the more difficult it is for the fuse to blow. As Figure 7 indicated, the current rating and the fuse I 2t is not in a proportional relationship. That is, as shown in Figure 7 if the current rating of the fuse is doubled from 200 (A) to 400 (A), the fuse I 2 t is increased by 7 times or more from 3 (A 2 s x 10 3 ) to 23 (A 2 s x 10 3 ). In other words, if the current rating of the fuse is made half from 400 (A) to 200 (A), the fuse I 2 t is decreased by 1 / 7 or less from 23 (A 2 s x 10 3 ) to 3 (A 2 s x 10 3 ). On the other hand, if the current rating of the fuse is 200 (A), the fuse does not open even if a current of 200 (A) continues to flow.

[0051] For example, if the current rating of the DC fuse 6 is reduced to half, the DC fuse 6 can be made to fuse several times faster. In the present application, in view of the properties of the DC fuse 6 described above, the capacity of each inverter unit 30 is actively reduced to make the DC fuse 6 fuse faster. In addition, Figure 7 The two numbers on the right side of the table of FIG. 10 are less relevant to the present application, and thus the description thereof is omitted here.

[0052] Figure 8 is a diagram showing a configuration example of a conventional power converter 100 relating to a comparative example and a configuration example of the power converter 1 relating to an embodiment. Figure 8 (a) of FIG. 10 is a diagram showing a configuration example of the conventional power converter 100 relating to a comparative example. Figure 8 (b) of FIG. 10 is a diagram showing a configuration example of the power converter 1 relating to an embodiment.

[0053] In addition, in the power converter 100 shown in (a) of FIG. 10 and the power converter 1 shown in (b) of FIG. 10, both are premised on the semiconductor elements 40 being 16. Figure 8 Figure 8 According to (a) of FIG. 10, the conventional power converter 100 relating to a comparative example has four inverter units 130 connected in parallel. Since the semiconductor elements 40 are premised on being 16, four semiconductor elements 40 are disposed in each inverter unit 130. The DC fuse 106 uses a product having a rated current that matches the capacity of the inverter unit 130.

[0054] According to (b) of FIG. 10, the power converter 1 relating to an embodiment has one inverter unit 30. The DC fuse 6 uses a product having a rated current that matches the capacity of the inverter unit 30. Figure 8 According to (b) of FIG. 10, the power converter 1 relating to an embodiment has one inverter unit 30. The DC fuse 6 uses a product having a rated current that matches the capacity of the inverter unit 30.

[0055] Figure 8 ​​(b), the power converter 1 is connected in parallel with eight inverter units 30. Since the number of semiconductor elements 40 is 16, two semiconductor elements 40 are arranged in each inverter unit 30. The DC fuse 6 uses a product having a rated current matching the capacity of the inverter unit 30.

[0056] If the power converter 100 shown in (a) is compared with the power converter 1 shown in (b), Figure 8 Figure 8 the number of inverter units 30 is half compared with the inverter units 130. Therefore, the capacity of the inverter units 30 is twice compared with the inverter units 130. Thus, in the power converter 1 relating to the present embodiment, the current rating of the DC fuse 6 can be made half compared with the current rating of the DC fuse 106 of the power converter 100 relating to the comparative example. As explained in Figure 7 , if the current rating of the DC fuse 6 is made half, the fusing I 2 t indicating the ease of fusing of the fuse drops to a fraction. Thus, the DC fuse 6 relating to the present embodiment is fused several times faster compared with the DC fuse 106 relating to the comparative example.

[0057] Figure 9 is a graph showing an operation example of the DC current and the DC voltage when a short-circuit fault occurs in the conventional power converter 100 relating to the comparative example shown in Figure 8

[0058] Figure 9 (a) of (a) of the conventional power converter 100 relating to the comparative example shown in (a) of Figure 8 Figure 9 (a) of (a) of the conventional power converter 100 relating to the comparative example shown in (a) of Figure 8 Figure 9 Figure 9 In (a) of (a), an operation example of the DC current and the DC voltage when a short-circuit fault occurs in one of the four inverter units 130 connected in parallel is shown. In the device shown in (a) of (a), a semiconductor element 40 having an element rating of 1700 V is used.

[0059] In (a) of (a), an operation example of the DC current and the DC voltage when a short-circuit fault occurs in one of the four inverter units 130 connected in parallel is shown. In the device shown in (a) of (a), a semiconductor element 40 having an element rating of 1700 V is used. Figure 9 ​​​​​In (a), the DC fuse 106 blows 220 microseconds after the short-circuit fault occurs. However, after the fuse blows, the DC voltage spikes, reaching a peak of 3.1 kV. This is because the DC fuse 106 has a high current rating (1100 A), so the blown fuse... 2 The voltage t is also relatively large, resulting in a longer time until the DC fuse 106 blows. Consequently, the DC voltage rises after the DC fuse 106 blows.

[0060] In addition, Figure 9 In the case of the device shown in (a), a semiconductor element 40 with a rated value of 1700V is used as described above. At this time, there is no problem when the 3.1kV voltage is applied equally to the upper arm 2 and lower arm 2 of the other normal semiconductor elements 40. However, in the event of such an accident, an unbalanced waveform may occur, and in such a case, if a 3.1kV DC voltage is applied, the semiconductor element 40 may be damaged under overvoltage. Therefore, in the conventional power converter 100 of the comparative example, secondary damage to the semiconductor element 40 also occurs in the other normal inverter units 30.

[0061] Figure 9 (b) indicates that in Figure 8 (b) shows an example of the operation of DC current and DC voltage in a power converter 1 according to one embodiment when a short-circuit fault occurs. Figure 9 (b) indicates that in such a case Figure 8 The diagram shows an example of DC current and DC voltage operation when a short-circuit fault occurs, as illustrated in (b) where the number of inverter units 30 connected in parallel is relatively large (8 units composed of 2 elements connected in parallel). Figure 9 (b) illustrates an example of DC current and DC voltage operation when one of the eight inverter units 30 connected in parallel experiences a short-circuit fault. Additionally, in Figure 9 In the device shown in (b), with Figure 9 The device shown in (a) also uses a semiconductor element 40 with an element rating of 1700V.

[0062] exist Figure 9 In (b), DC fuse 6 blows rapidly after a short-circuit fault occurs. The DC voltage rise is relatively small, at 1.47 kV. This is because the current rating of DC fuse 6 is relatively small (525 A), so the blowing of fuse 6 is relatively quick. 2 t is also smaller, and the time until DC fuse 6 blows is several times shorter than that of DC fuse 106.

[0063] In addition, Figure 9In the case of the device shown in (b), the semiconductor element 40 having an element rating of 1700 V is used as described above. At this time, even if the voltage of 1.47 kV is continuously applied to the upper arm 2 and the lower arm 2 of the other normal semiconductor element 40 in an unbalanced waveform, since it is a voltage lower than the element rating, the semiconductor element 40 will not be damaged by an overvoltage. Therefore, in the power converter 1 relating to the present embodiment, element damage of the secondary semiconductor element 40 can also be suppressed in the other normal inverter unit 30.

[0064] As Figure 9 (a) and Figure 9 (b) show, as long as the rise in the inrush current from the battery 10 can be suppressed, the subsequent rise in the direct current voltage can also be suppressed. If the inrush current from the battery 10 rises greatly, the energy is stored in the impedance 7, mainly the inductance, of the wiring between the battery 10 and the power converter 1 in proportion to the square of the current. It is conceivable that, if a current of I flows in the reactor, the inductor of the inductance L, the energy of 1 / 2 LI 2 is stored, and the voltage rise is affected by such energy inflow.

[0065] According to the above, since the power converter 1 of 2-element parallel 8-unit configuration can reduce the rating of the fusing I 2 t of the direct current fuse 6 several times compared to the power converter 100 of 4-element parallel 4-unit configuration, the direct current fuse 6 is fused faster, and the rise in the direct current voltage can be suppressed. This is based on the fusing characteristics of the direct current fuse 6. That is, it is based on the fact that the current rating and the fusing I 2 t of the direct current fuse 6 are not in a proportional relationship, the fusing I 2 t becomes twice or more when the current rating is made half, the fusing I 2 t becomes half or less, and the direct current fuse 6 fuses faster.

[0066] In addition, in order to realize a large-capacity power converter 1, first, the parallel configuration of each element and each unit is listed, and each pattern is analyzed. When the number of parallel inverter units 30 is small, the direct current fuse 6 fuses slowly, and there is a tendency for the direct current fuse 6 of the other normal inverter unit 30 to also fuse, and in addition, the rise in the direct current voltage is large. At this time, it is determined how many the number of parallel inverter units 30 is increased to, and the direct current fuse 6 of the other normal inverter unit 30 is not fused, and the rise in the direct current voltage is small. Furthermore, based on the determination result described above, a large-capacity power converter 1 is realized.

[0067] The case where the large-capacity power converter 1 cannot be realized is a case where the fly-up of the DC voltage is large and the DC fuses 6 of the other normal inverter units 30 are also fused. This is because, if the capacity of the inverter unit 30 is large, the number of the inverter units 30 in parallel is small and the number of the semiconductor elements 40 in parallel in one unit is large. This is because the larger the inverter unit 30, the larger the fuse I 2 t of one DC fuse 6, the slower the DC fuse 6 is fused and the fuses of the other normal inverter units 30 are also fused.

[0068] Therefore, the large-capacity power converter 1 according to the present embodiment requires the number of the inverter units 30 to be the number satisfying the condition that the DC fuses 6 of the other normal inverter units 30 are not fused at the time of the short-circuit analysis. As an example, the number of the inverter units 30 can be cited as the number larger than the number of the semiconductor elements 40. Further, as an example, the number of the inverter units 30 can be cited as the number larger than 4. Furthermore, as an example, the number of the inverter units 30 can be cited as 8 and the number of the semiconductor elements 40 can be cited as 2 as shown in the present embodiment.

[0069] <Effects of One Embodiment>

[0070] According to the present embodiment, it is possible to provide the power converter 1 which suppresses the occurrence of the secondary element damage of the normal inverter unit 30 by rapidly fusing the DC fuse 6 at the time of the element damage to suppress the rise of the DC voltage (DC link voltage).

[0071] <Supplementary Notes to Embodiments>

[0072] The features and advantages of the embodiments should be apparent from the detailed description. It is implied that the scope of the claims encompasses the features and advantages of the embodiments within the scope of the principles and the scope of the rights. Further, all modifications and changes which can be easily conceived by those having ordinary knowledge in the art should be easily conceived. Therefore, it is not intended to limit the scope of the embodiments having the inventive to the above, and appropriate modifications and equivalents included in the scope disclosed in the embodiments can be made.

[0073] Explanation of Reference Numerals

[0074] 1, 1A, 1B, 1C… Power converter (inverter); 2… Arm; 3… Leg; 4… DC capacitor (capacitor); 5… DC circuit breaker (circuit breaker); 6… DC fuse (fuse); 7… Impedance; 8… Short circuit fault (short circuit accident); 10… DC power supply (battery); 20… AC system; 30… Inverter unit (unit, single inverter unit, single unit); 40… Semiconductor element (element); 100… Power converter; 106… DC fuse (fuse); 130… Inverter unit (unit, single inverter unit, single unit); C… Neutral point; L… Inductor; N… Negative terminal; P… Positive terminal.

Claims

1. A power converter for converting power between a DC power supply consisting of a battery disposed on the DC side and an AC system disposed on the AC side, characterized in that, Each phase of the power converter has: Multiple inverter units, connected in parallel on the DC side to the DC power supply comprised of the battery, each having multiple semiconductor elements; and Multiple DC fuses are respectively installed in the circuit between the DC power supply and each inverter unit in the multiple inverter units. When a short circuit fault occurs in one of the inverter units, the fuses are blown in the circuit between the DC power supply and the inverter unit that has experienced the short circuit fault. The phases of the power converter are as follows: The number of the aforementioned multiple inverter units is the number that satisfies the condition that, when the DC fuse between the aforementioned DC power supply and the inverter unit experiencing the aforementioned short-circuit fault blows, none of the aforementioned DC fuses between the aforementioned DC power supply and the other multiple inverter units that have not experienced the aforementioned short-circuit fault will blow. The number of the aforementioned inverter units is greater than the number of the aforementioned semiconductor elements. The number of the aforementioned inverter units is 8, and the number of the aforementioned semiconductor elements is 2.

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