A three-level DC / DC fault isolation system

Abstract

The present application discloses a three-level DC / DC fault isolation system, which includes a three-level DC / DC parallel system, a plurality of isolation modules and an energy supply unit; the three-level DC / DC parallel system includes multiple groups of DC / DC units, the isolation modules are installed on the input side and / or the output side of the corresponding groups of DC / DC units, and the energy supply unit is connected to the output end of the three-level DC / DC parallel system; when any DC / DC unit has a short-circuit fault, all DC / DC units are blocked from driving; the isolation module of the faulty group disconnects the faulty DC / DC unit from the three-level DC / DC parallel system; during this process, the energy supply unit supplies energy to the load connected to the output end of the three-level DC / DC parallel system; when the faulty DC / DC unit is isolated, the remaining DC / DC units are unblocked and resume supplying energy to the load. When a fault occurs, by blocking the driving of all DC / DC units, the spread of the fault can be avoided. Subsequently, the faulty DC / DC unit is disconnected through the isolation module, which can ensure the operation safety of the subsequent three-level DC / DC parallel system after restarting.

Description

Technical Field

[0001] This application relates to the field of power electronics technology, and particularly to a three-level DC / DC fault isolation system. Background Art

[0002] The parallel technology of power electronic converters can effectively improve the reliability of the system. For example, three-level DC / DC is widely used in fields such as photovoltaic, UPS, and fuel cells. When a unit fails, if the system isolation is not timely, the fault will not only affect the faulty module, but also cause the fault to spread, making other modules unable to work properly, resulting in the output voltage unable to be maintained and the collapse of the entire system. Therefore, fault isolation is a very important link in system fault tolerance. Summary of the Invention

[0003] One of the purposes of this application is to provide a system that can isolate the fault point when a fault occurs in a three-level DC / DC parallel system.

[0004] To achieve at least one of the above purposes, the technical solution adopted in this application is: a three-level DC / DC fault isolation system, including a three-level DC / DC parallel system, a plurality of isolation modules, and an energy supply unit; the three-level DC / DC parallel system includes multiple groups of DC / DC units, the isolation modules are installed on the input side and / or output side of the corresponding group of DC / DC units, and the energy supply unit is connected to the output end of the three-level DC / DC parallel system; when any of the DC / DC units has a short-circuit fault, all the DC / DC units are driven to block; the isolation module in the faulty group disconnects the faulty DC / DC unit from the three-level DC / DC parallel system; during this process, the energy supply unit supplies energy to the load connected to the output end of the three-level DC / DC parallel system; after the faulty DC / DC unit is isolated, the remaining DC / DC units are unblocked and resume power supply to the load.

[0005] Preferably, the isolation module includes an isolation unit; the isolation unit is connected to the input side of the DC / DC unit.

[0006] Preferably, the isolation module includes two isolation units; the two isolation units are respectively connected to the input side and the output side of the DC / DC unit; or, the two isolation units are both connected to the output side of the DC / DC unit.

[0007] Preferably, the isolation unit adopts any one of a fuse, a contactor, an electronic switch, and a diode.

[0008] Preferably, when the isolation unit uses a fuse, the isolation module further includes an auxiliary fusing unit; the auxiliary fusing unit is adapted to form a fusing circuit with the fuse; when the DC / DC unit fails, the fusing circuit is adapted to accelerate the fusing of the fuse located in the faulty group.

[0009] Preferably, the three-level DC / DC parallel system is an N + n redundant system; where N represents the number of normally operating DC / DC units, and n represents the number of standby DC / DC units.

[0010] Preferably, when the isolation unit uses a fuse, the value of N is greater than 6.

[0011] Preferably, when the three-level DC / DC parallel system is operating normally, the power supply unit is adapted to store energy through the output terminal of the three-level DC / DC parallel system.

[0012] Preferably, the power supply unit includes a battery pack or a supercapacitor bank; the battery pack or the supercapacitor bank is adapted to be directly connected to the output terminal of the three-level DC / DC parallel system.

[0013] Preferably, the power supply unit includes a bidirectional DC / DC unit and a battery pack or a supercapacitor bank; the battery pack or the supercapacitor bank is adapted to be connected to the output terminal of the three-level DC / DC parallel system through the bidirectional DC / DC unit.

[0014] Compared with the prior art, the beneficial effects of the present application are as follows:

[0015] (1) In the present application, by installing an isolation module on each DC / DC unit, when a DC / DC unit fails, all DC / DC units can be driven to block, so as to avoid the spread of the fault. Subsequently, the faulty DC / DC unit is disconnected from the three-level DC / DC parallel system through the corresponding isolation module, thereby ensuring the operation safety of the subsequent three-level DC / DC parallel system after restart.

[0016] (2) At the same time, in the present application, by connecting a power supply unit to the output terminal of the three-level DC / DC parallel system, when all DC / DC units are driven to block, the power supply unit can continue to supply power to the load to ensure the normal operation of the load.

[0017] Figure 1 Schematic diagram of circuit analysis when an IGBT unit fails in an existing three-level DC / DC Figure 1 。

[0018] Figure 2Schematic diagram of circuit analysis when an IGBT unit fails in an existing three-level DC / DC Figure 2 。

[0019] Figure 3 Schematic diagram of circuit analysis when a diode fails in an existing three-level DC / DC Figure 1 。

[0020] Figure 4 Schematic diagram of circuit analysis when a diode fails in an existing three-level DC / DC Figure 2 。

[0021] Figure 5 Schematic diagram of the circuit installation structure of one embodiment of the present invention Figure 1 。

[0022] Figure 6 For the present invention Figure 5 Schematic diagram of the circuit installation structure for accelerating fusing in the illustrated embodiment

[0023] Figure 7 Schematic diagram of the circuit installation structure of another embodiment of the present invention

[0024] Figure 8 For the invention Figure 7 Schematic diagram of the circuit installation structure for accelerating fusing in the illustrated embodiment

[0025] Figure 9 Schematic diagram of the circuit installation structure of still another embodiment of the present invention

[0026] Figure 10 Schematic diagram of the structure of one embodiment of the energy supply unit in the present invention

[0027] Figure 11 Schematic diagram of the structure of another embodiment of the energy supply unit in the present invention

[0028] In the figure: DC / DC unit 100, first converter 110, second converter 120, load 200, first isolation unit 310, energy supply unit 320, auxiliary fusing unit 330, second isolation unit 340. Detailed implementation manners

[0029] Next, in combination with the detailed implementation manners, the present application will be further described. It should be noted that, on the premise of no conflict, any combination of the following-described embodiments or technical features can form a new embodiment.

[0030] In the description of the present application, it should be noted that for the orientation terms, such as the terms "center", "lateral", "longitudinal", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", etc., indicating the orientation and positional relationship are based on the orientation or positional relationship shown in the drawings. This is only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and should not be construed as limiting the specific protection scope of the present application.

[0031] It should be noted that the terms "first", "second", etc. in the description and claims of the present application are used to distinguish similar objects and do not necessarily need to describe a specific order or sequence.

[0032] One preferred embodiment of the present application is, for example Figures 5 to 11 As shown, a three-level DC / DC fault isolation system includes a three-level DC / DC parallel system, a plurality of isolation modules, and an energy supply unit 320. The three-level DC / DC parallel system includes multiple groups of DC / DC units 100; the isolation modules are installed on the input side and / or output side of the corresponding groups of DC / DC units 100; the energy supply unit 320 is connected to the output end of the three-level DC / DC parallel system. When any DC / DC unit 100 has a short-circuit fault, all DC / DC units 100 are blocked from driving; the isolation module located in the faulty group can disconnect the faulty DC / DC unit 100 from the three-level DC / DC parallel system to achieve isolation between the faulty group of DC / DC units 100 and the three-level DC / DC parallel system; during this process, the energy supply unit 320 supplies energy to the load 200 connected to the output end of the three-level DC / DC parallel system. After the faulty DC / DC unit 100 is isolated, the remaining DC / DC units 100 are unblocked and resume supplying energy to the load 200. At the same time, after restarting, the three-level DC / DC parallel system without faulty DC / DC units 100 can also charge the energy supply unit 320.

[0033] It can be understood that multiple groups of DC / DC units 100 are connected in parallel with each other. Thus, when any one or more groups of DC / DC units 100 have a short-circuit fault, forced series connection may occur between the parallel-connected multiple groups of DC / DC units 100, which may further cause abnormal operation of other DC / DC units 100. Among them, the DC / DC unit 100 includes a first converter 110, an IGBT unit group, a diode group, and a second converter 120. The common short-circuit faults of the DC / DC unit 100 include IGBT unit short-circuit faults and diode short-circuit faults.

[0034] In this embodiment, as Figures 5 to 10 shown, when a short - circuit fault occurs in the DC / DC unit 100, it will cause the output voltage of the three - level DC / DC parallel system to become abnormal. Therefore, to transform the circuit of the traditional three - level DC / DC parallel system, it is first necessary to stabilize its output voltage; that is, an energy - supply unit 320 is connected to the output end of the traditional three - level DC / DC parallel system. When the three - level DC / DC parallel system is working normally, the energy - supply unit 320 can store energy through the three - level DC / DC parallel system; when a short - circuit fault occurs in the DC / DC unit 100, the energy - supply unit 320 can maintain the voltage stability of the output end of the three - level DC / DC parallel system to the load 200. Moreover, during the subsequent driving blocking process of the DC / DC unit 100, the energy - supply unit 320 can continue to supply energy to the load 200 to ensure that the load 200 continues to work normally during the driving blocking process of the DC / DC unit 100.

[0035] One embodiment of the present application, as Figure 10 shown, the energy - supply unit 320 includes a battery pack or a super - capacitor bank; the battery pack or the super - capacitor bank can be directly connected to the output end of the three - level DC / DC parallel system. Thus, when the three - level DC / DC parallel system is working normally, the battery pack or the super - capacitor bank can be charged and stored with energy. When a short - circuit fault occurs in the DC / DC unit 100, the battery pack or the super - capacitor bank can release the electric energy stored in itself and supply it to the load 200.

[0036] Of course, in order to further improve the voltage stability of the energy - supply unit 320 during the energy - supply process and the voltage stability of the three - level DC / DC parallel system for charging the energy - supply unit 320. Another embodiment of the present application, as Figure 11 shown, the energy - supply unit 320 includes a bidirectional DC / DC unit and a battery pack or a super - capacitor bank; the battery pack or the super - capacitor bank can be connected to the output end of the three - level DC / DC parallel system through the bidirectional DC / DC unit.

[0037] For the convenience of understanding the subsequent content, a fault analysis of the traditional three - level DC / DC parallel system can be carried out first.

[0038] To simplify the narrative content, as Figures 1 to 4 shown, two sets of DC / DC units 100 can be taken and marked as #1 and #2 respectively; and it is assumed that the DC / DC unit 100 in the #1 group fails.

[0039] (1) IGBT fault analysis.

[0040] The IGBT unit group includes two IGBT units. The two IGBT units of the DC / DC unit 100 in Group #1 can be respectively labeled as S1 and S2. The two IGBT units of the DC / DC unit 100 in Group #2 are respectively labeled as S3 and S4.

[0041] As Figure 1 and Figure 2 shown, when a short - circuit fault occurs in the IGBT unit labeled as S1, the first converter 110 and the second converter 120 of the DC / DC unit 100 in Group #1 are forced to be connected together. Due to the non - isolation of the system, the first converter 110 and the second converter 120 of the DC / DC unit 100 in Group #2 are also forced to be connected together, thus causing abnormal operation of the DC / DC unit 100 in Group #2.

[0042] Specifically, as Figure 1 and Figure 2 shown, whether the IGBT unit labeled as S3 in the DC / DC unit 100 of Group #2 is turned off and the IGBT unit labeled as S4 is turned on; or the IGBT unit labeled as S3 is turned on and the IGBT unit labeled as S4 is turned off. Loops as shown by the thickened lines in Figure 1 and Figure 2 can be respectively formed between the two groups of DC / DC units 100; meanwhile, the direction indicated by the dotted - line arrow in the figure is the current direction of the loop. Thus, the short - circuit current of the faulty Group #1 will be introduced into the normal Group #2, causing the inductor L4 to be continuously charged and the current to increase more and more with time accumulation. When the current accumulates to exceed the set upper threshold, all IGBT unit drives have to be blocked. At this time, the upper bus voltage of the two groups of DC / DC units 100 gradually drops to zero, and the lower bus voltage is equal to the input voltage, and the entire three - level DC / DC parallel system shuts down.

[0043] (2) Diode fault analysis.

[0044] The diode group includes two diodes. The two diodes of the DC / DC unit 100 labeled as #1 can be respectively labeled as D1 and D2. The two diodes of the DC / DC unit 100 labeled as #2 are respectively labeled as D3 and D4.

[0045] As Figure 3 and Figure 4 shown, when the diode labeled as D1 has a short - circuit fault, the first converter 110 and the second converter 120 of the DC / DC unit 100 in Group #1 are forced to be connected together. Due to the non - isolation of the system, the first converter 110 and the second converter 120 of the DC / DC unit 100 in Group #2 are also forced to be connected together, thus causing abnormal operation of the DC / DC unit 100 labeled as #2.

[0046] Specifically, as Figure 3 shown, when the IGBT unit marked as S3 in the DC / DC unit 100 of group #2 is turned on and the IGBT unit marked as S4 is turned off, a short - circuit loop as indicated by the bold line in Figure 3 can be formed between the two groups of DC / DC units 100. At the same time, the direction indicated by the dotted arrow in the figure is the current direction of the short - circuit loop. The inductor L1 can be directly spanned between the input side and the output side of the DC / DC unit 100, thereby causing the short - circuit current to flow reversely, enabling the upper - bus capacitor to rapidly charge the inductors L1 and L3.

[0047] Similarly, as Figure 4 shown, when the IGBT unit marked as S3 in the DC / DC unit 100 of group #2 is turned off and the IGBT unit marked as S4 is turned on, a short - circuit loop as indicated by the bold line in Figure 4 can be formed between the two groups of DC / DC units 100; at the same time, the direction indicated by the dotted arrow in the figure is the current direction of the loop. The current of the inductor L1 continues to flow through the diode D3. Therefore, after the diode fails, it needs to be immediately isolated to prevent affecting the normal operation of other units.

[0048] As can be seen from the above, there are three specific short - circuit fault situations in the three - level DC / DC parallel system. First, the IGBT unit has a short - circuit fault and the diode does not fail; second, the IGBT unit does not have a short - circuit fault and the diode has a short - circuit fault; third, both the IGBT unit and the diode have faults. Therefore, the three - level DC / DC fault isolation system of this application needs to meet the requirement of isolating the above three short - circuit fault situations.

[0049] Next, the three - level DC / DC fault isolation system of this application can be described in combination with specific embodiments. To simplify the description content, only two DC / DC units 100 of the three - level DC / DC parallel system are taken and marked as #1 and #2 respectively.

[0050] Embodiment 1: As Figure 5 shown, the isolation module includes an isolation unit, which can be defined as the first isolation unit 310, and the first isolation unit 310 can use a fuse. As Figures 1 to 4 known, when there is a short - circuit fault in the IGBT unit or the diode, the DC / DC unit 100 of the faulty group is forcibly connected to the DC / DC unit 100 of the normal group to form a short - circuit loop. Thus, the fuse can be connected to the formed short - circuit loop, and then the fuse is melted by the short - circuit current to disconnect the connection between the DC / DC unit 100 of the faulty group and the DC / DC unit of the normal group.

[0051] In this embodiment, as Figure 5 and Figure 6 shown, the fuse is arranged on the input side of the DC / DC unit 100, and the number of fuses is two. The two fuses are respectively connected to the positive and negative busbars of the DC / DC unit 100.

[0052] Specifically, as Figure 5 shown, the two fuses on the input side of the DC / DC unit 100 in the #1 group are respectively marked as F1 and F2; the two fuses on the input side of the DC / DC unit 100 in the #2 group are respectively marked as F3 and F4.

[0053] Assume that the IGBT unit marked as S1 in the #1 group has a short - circuit fault; after the fault is successfully detected, the driving of all IGBT units included in the DC / DC units 100 of all groups is blocked. Thus, a short - circuit loop including fuse F1 and fuse F3 can be formed; at this time, the voltage of the input - side power supply is greater than the half - busbar voltage, so a short - circuit current is formed in the short - circuit loop; because there are two diode loops for shunting at the negative end, the fuse F1 at the positive end melts first, and then the fault group #1 and the entire three - level DC / DC parallel system are disconnected.

[0054] Assume that the diode D1 in the #1 group has a short - circuit fault; after the fault is successfully detected, the driving of all IGBT units included in the DC / DC units 100 of all groups is blocked. Subsequently, the IGBT unit marked as S3 in the #2 group is turned on, so that a short - circuit loop is generated between the entire fault group #1 and the normal group #2, and then the fuse F1 is melted.

[0055] Assume that the IGBT unit marked as S1 and the diode D1 in the #1 group have short - circuit faults simultaneously; after the fault is successfully detected, the driving of all IGBT units included in the DC / DC units 100 of all groups is blocked. Thus, a short - circuit loop including fuse F1 and fuse F3 can be formed; at this time, the voltage of the input - side power supply is greater than the half - busbar voltage, so a short - circuit current is formed in the short - circuit loop; because there are two diode loops for shunting at the negative end, the fuse F1 at the positive end melts first, and then the fault group #1 and the entire three - level DC / DC parallel system are disconnected.

[0056] During this process, the power supply unit 320 and the load 200 are temporarily connected to supply power and maintain power supply; at the same time, the power supply unit 320 can also be connected to the short - circuit loop to absorb the short - circuit current flowing into the bus, thereby supporting the bus. Subsequently, all IGBT units release the drive block, but the DC / DC units 100 of the faulty group are disconnected from the DC / DC units 100 of the remaining normal groups due to the open circuit of the positive bus on the input side. Thus, the restarted three - level DC / DC parallel system can resume power supply to the load 200 through the DC / DC units 100 of the normal group; at the same time, the restarted three - level DC / DC parallel system can also charge and store energy in the power supply unit 320.

[0057] It can be understood that, in order to meet the above isolation requirements, the input - side power supply of the three - level DC / DC parallel system has the ability to draw out short - circuit current; at the same time, the power supply unit 320 has the ability to absorb short - circuit current, and the diode has the ability to withstand the short - circuit current shunt.

[0058] It should be known that when only the diode D1 has a short - circuit fault, after all IGBT units are blocked from driving, no short - circuit loop will be generated between the #1 group and the #2 group. Therefore, in order to ensure that the fuse F1 connected to the faulty diode can be melted, a short - circuit loop needs to be constructed. That is, the IGBT unit marked as S3 in the normal group #2 is turned on, so that a short - circuit loop including the faulty diode and the fuse connected to it can be formed between the #1 group and the #2 group. Since the conduction direction of the diode D4 is opposite to the current direction of the required short - circuit loop, turning on the IGBT unit marked as S4 in the #2 group cannot form the required short - circuit loop.

[0059] It can also be understood that if the fuse is set on the output side of the DC / DC unit 100. By Figures 1 to 4It can be known that three fuses are required, and the three fuses are respectively connected to the positive and negative busbars and the neutral line. When only the IGBT unit has a short-circuit fault, the fuse located on the neutral line will be blown; however, after the IGBT unit is unlocked, the faulty DC / DC unit 100 can still be connected to the three-level DC / DC parallel system through the positive and negative busbars. When only the diode has a short-circuit fault, the fuse located on the positive busbar or the negative busbar will be blown; however, after the IGBT unit is unlocked, the faulty DC / DC unit 100 can still be connected to the three-level DC / DC parallel system through the neutral line and the unfused negative busbar or positive busbar. Only when both the IGBT unit and the diode have short-circuit faults at the same time, all the fuses of the DC / DC unit 100 in the faulty group can be blown, thereby isolating the faulty DC / DC unit 100 from the three-level DC / DC parallel system. Therefore, in order to meet the fault isolation requirements of the three-level DC / DC parallel system, the fuse can only be set on the input side of the DC / DC unit 100.

[0060] In this embodiment, the three-level DC / DC parallel system is an N + n redundant system; where N represents the number of normally operating DC / DC units 100, and n represents the number of standby DC / DC units 100; when the isolation unit 310 uses a fuse, the value of N needs to be greater than 6; at the same time, the value of n is generally greater than or equal to 1.

[0061] It can be understood that after the DC / DC unit 100 in the faulty group is isolated and disconnected, restarting the three-level DC / DC parallel system will cause the load current of each group of DC / DC units 100 to increase when the input-side voltage remains unchanged. If the number of remaining groups of DC / DC units 100 in the three-level DC / DC parallel system is too small, it will cause the increased load current of each group of DC / DC units 100 to be overloaded, and then cause the fuses of the DC / DC units 100 in the normal group to also blow, causing the entire three-level DC / DC parallel system to shut down again. Therefore, when the first isolation unit 310 uses a fuse, it is necessary to ensure that the three-level DC / DC parallel system includes a sufficient number of groups of DC / DC units 100, so that after some DC / DC units 100 fail and are isolated, the load current shared by the remaining DC / DC units 100 will not be overloaded.

[0062] In this embodiment, as Figure 6 shown, when the first isolation unit 310 uses a fuse, the isolation module further includes an auxiliary fusing unit 330; the auxiliary fusing unit 330 can form a fusing circuit with the fuse. When the DC / DC unit 100 fails, the fusing circuit can accelerate the fusing of the fuse located in the faulty group.

[0063] It is understandable that when the fuse of the DC / DC unit 100 in the fault group is blown, other components in the short-circuit loop are all subjected to the short-circuit current. Therefore, in order to avoid damage to other components, the fuse needs to be blown as quickly as possible.

[0064] Specifically, Figure 6 As shown, the auxiliary fuse unit 330 can use a thyristor, and the number of thyristors is two. For the convenience of description, the two thyristors located in group #1 can be marked as T11 and T12, respectively, and the two thyristors located in group #2 can be marked as T21 and T22, respectively. Among them, the input ends of the thyristor T11 and the thyristor T21 are connected to the input side positive bus of the three-level DC / DC parallel system, and the output ends of the thyristor T11 and the thyristor T21 are respectively connected to the output side negative bus of the corresponding DC / DC unit 100. The input ends of the thyristor T12 and the thyristor T22 are respectively connected to the output side positive bus of the corresponding DC / DC unit 100; the output ends of the thyristor T12 and the thyristor T22 are connected to the input side negative bus of the three-level DC / DC parallel system.

[0065] Initially, all thyristors are in the off state. When a short-circuit fault occurs in the DC / DC unit 100 of group #1, all IGBT units included in all DC / DC units 100 are driven and blocked; at the same time, the thyristors in group #1 are turned on. Taking the short-circuit fault of the IGBT unit marked as S1 and / or the diode D1 as an example, the fuse F1 and the inductor L1 form a fusing circuit through the thyristor T11, and then the limiting current generated by the fusing circuit can quickly blow the fuse F1. By blowing the fuse F1, the fault group #1 is quickly isolated from the three-level DC / DC parallel system; thereby, the time that other components withstand the short-circuit current can be effectively shortened to ensure the safety of other components.

[0066] Embodiment 2: Figure 7 As shown, the isolation module includes two isolation units, which can be defined as a first isolation unit 310 and a second isolation unit 340. The first isolation unit 310 can be a contactor or an electronic switch, and the second isolation unit 340 can be a fuse. Figures 1 to 4 It can be seen that when there is a short-circuit fault in an IGBT unit or a diode, the DC / DC unit 100 in the fault group is forcibly connected to the DC / DC unit 100 in the normal group to form a short-circuit loop. Therefore, the first isolation unit 310 and the second isolation unit 340 can be connected to the short-circuit loop formed, and then the connection between the DC / DC unit 100 in the fault group and the DC / DC unit in the normal group can be disconnected through the first isolation unit 310 and the second isolation unit 340.

[0067] In this embodiment, as Figure 7 shown, the first isolation unit 310 can be disposed on the input side of the DC / DC unit 100. The number of contactors or electronic switches used in the first isolation unit 310 is two, and they are respectively connected to the positive and negative busbars. The second isolation unit 340 can be disposed on the output side of the DC / DC unit 100. The number of fuses used in the second isolation unit 340 is one, and the fuse is connected to the neutral line.

[0068] Specifically, as Figure 7 shown, the two contactors or electronic switches on the input side of the DC / DC unit 100 in Group #1 are respectively marked as S11 and S12, and the fuse on the output side is marked as F1. The two contactors or electronic switches on the input side of the DC / DC unit 100 in Group #2 are respectively marked as S21 and S22, and the fuse on the output side is marked as F2.

[0069] Initially, all contactors or electronic switches are in the normally closed state.

[0070] Suppose the IGBT unit marked as S1 in Group #1 has a short - circuit fault; after successful fault detection, the drive of all IGBT units included in the DC / DC units 100 of all groups is blocked. At the same time, the contactor or electronic switch marked as S11 connected to the faulty group is opened or the fuse F1 is melted during the formation of the short - circuit circuit. Thus, the faulty group #1 and the entire three - level DC / DC parallel system are disconnected.

[0071] Suppose the diode D1 in Group #1 has a short - circuit fault; after successful fault detection, the drive of all IGBT units included in the DC / DC units 100 of all groups is blocked. At the same time, the contactor or electronic switch marked as S11 connected to the faulty group is opened; or the IGBT unit marked as S3 in Group #2 is turned on, so that a short - circuit loop is generated between the entire faulty group #1 and the normal group #2, and then the fuse F1 is melted. Finally, the faulty group #1 and the entire three - level DC / DC parallel system can be disconnected

[0072] Suppose the IGBT unit marked as S1 and the diode D1 in Group #1 have short - circuit faults simultaneously; after successful fault detection, the drive of all IGBT units included in the DC / DC units 100 of all groups is blocked. At the same time, the contactor or electronic switch marked as S11 connected to the faulty group is opened or the fuse F1 is melted during the formation of the short - circuit circuit. Thus, the faulty group #1 and the entire three - level DC / DC parallel system are disconnected.

[0073] It can be understood that, in order to avoid overload, the number of groups of DC / DC units 100 included in the three-level DC / DC parallel system in this embodiment needs to meet the above-mentioned value requirement of the redundant system N+n.

[0074] In this embodiment, Figure 8 As shown, when the second isolation unit 340 uses a fuse, the isolation module further includes an auxiliary fuse unit 330; the auxiliary fuse unit 330 can form a fuse circuit with the fuse. When the DC / DC unit 100 fails, the fuse circuit can accelerate the fuse in the fault group to melt.

[0075] It is understandable that when the fuse of the DC / DC unit 100 in the fault group is blown, other components in the short-circuit loop are all subjected to the short-circuit current. Therefore, in order to avoid damage to other components, the fuse needs to be blown as quickly as possible.

[0076] Specifically, Figure 8 As shown, the auxiliary fuse unit 330 may be a thyristor, and the number of thyristors is two. For the convenience of description, the two thyristors in group #1 may be marked as T11 and T12, and the two thyristors in group #2 may be marked as T21 and T22.

[0077] The input ends of thyristors T11 and T21 are connected to the positive busbar on the input side of the three-level DC / DC parallel system; the output ends of thyristors T11 and T21 are respectively connected to the ends of fuses F1 and F2 close to the IGBT unit group. The output ends of thyristors T12 and T22 are connected to the negative busbar on the output side of the three-level DC / DC parallel system; the input ends of thyristors T12 and T22 are respectively connected to the ends of fuses F1 and F2 far from the IGBT unit group.

[0078] Initially, all thyristors are in the off state. When a short circuit fault occurs in the DC / DC unit 100 of group #1, all IGBT units included in all DC / DC units 100 are driven and blocked; at the same time, the thyristors in group #1 are turned on, and the fuse F1 forms a fusing circuit through the thyristors T11 and T12, and then the limiting current generated by the fusing circuit can quickly blow the fuse F1. By blowing the fuse F1, the fault group #1 is quickly isolated from the three-level DC / DC parallel system; thereby, the time for other components to withstand the short-circuit current can be effectively shortened to ensure the safety of other components.

[0079] Embodiment 3: Figure 9As shown, the isolation module includes two isolation units, which can be respectively defined as the first isolation unit 310 and the second isolation unit 340. The first isolation unit 310 can be a diode, and the second isolation unit 340 can be a contactor or an electronic switch. From Figures 1 to 4 it can be seen that when a short - circuit fault occurs in an IGBT unit or a diode, the DC / DC unit 100 of the faulty group forcibly connects to the DC / DC unit 100 of the normal group to form a short - circuit loop. Thus, the first isolation unit 310 and the second isolation unit 340 can be connected to the formed short - circuit loop, and then the connection between the DC / DC unit 100 of the faulty group and the DC / DC unit of the normal group can be disconnected through the first isolation unit 310 and the second isolation unit 340.

[0080] In this embodiment, as Figure 9 shown, both the first isolation unit 310 and the second isolation unit 340 can be arranged on the output side of the DC / DC unit 100; the number of diodes used in the first isolation unit 310 is two and they are respectively connected to the positive and negative busbars; the number of contactors or electronic switches used in the second isolation unit 340 is one and it is connected to the neutral line.

[0081] Specifically, as Figure 9 shown, the two diodes on the output side of the DC / DC unit 100 of group #1 are respectively marked as D11 and D12, and the contactor or electronic switch is marked as S11. The two diodes on the output side of the DC / DC unit 100 of group #2 are respectively marked as D21 and D22, and the contactor or electronic switch is marked as S22.

[0082] Initially, all contactors or electronic switches are in the normally - closed state.

[0083] Suppose the IGBT unit marked as S1 in group #1 has a short - circuit fault; from Figure 1 and Figure 2 it can be seen that a short - circuit circuit passing through the neutral line on the output side of the DC / DC unit 100 of the faulty group can be formed. After successful fault detection, all IGBT units included in the DC / DC units 100 of all groups are driven to be blocked. At the same time, the contactor or electronic switch marked as S11 connected to the faulty group is opened, and then the short - circuit loop can be disconnected to achieve the disconnection between the faulty group #1 and the entire three - level DC / DC parallel system.

[0084] Suppose the diode D1 in group #1 has a short - circuit fault. After successful fault detection, the IGBT units of all DC / DC units 100 are blocked; from Figure 4It can be seen that a reverse short - circuit loop can theoretically be formed between Group #1 and Group #2. And diodes D11 and D21 are both located in the above - mentioned short - circuit loop. Since the conduction direction of diode D11 is opposite to the current direction of the short - circuit loop, the short - circuit loop cannot conduct. That is, through the reverse cut - off of diode D11, when a short - circuit fault occurs in diode D1, a short - circuit loop cannot be formed, thereby realizing the disconnection of the fault group #1 and the three - level DC / DC parallel system.

[0085] Suppose that the IGBT unit marked as S1 and diode D1 in Group #1 simultaneously have short - circuit faults; after successful fault detection, the drive of all IGBT units included in the DC / DC units 100 of all groups is blocked. At the same time, the contactor or electronic switch marked as S11 connected to the fault group is opened; at the same time, the conduction direction of diode D11 is opposite to the current direction of the short - circuit loop, so that the short - circuit loop cannot conduct. That is, through the reverse cut - off of diode D11, when a short - circuit fault occurs in diode D1, a short - circuit loop cannot be formed. Furthermore, the fault group #1 and the entire three - level DC / DC parallel system are disconnected.

[0086] It can be understood that there are various embodiments for realizing the fault isolation of the three - level DC / DC parallel system, including but not limited to the above - mentioned three.

[0087] The above describes the basic principle, main features and advantages of the present application. Those skilled in the art should understand that the present application is not limited by the above - mentioned embodiments. What is described in the above - mentioned embodiments and the specification is only the principle of the present application. Without departing from the spirit and scope of the present application, the present application will have various changes and improvements, and these changes and improvements all fall within the scope of the present application claimed. The scope of protection claimed by the present application is defined by the appended claims and their equivalents.

Claims

1. A three-level DC / DC fault isolation system, characterized in that, Comprising: A three-level DC / DC parallel system, the three-level DC / DC parallel system including multiple groups of DC / DC units; Multiple isolation modules, the isolation modules being installed on the input side and / or output side of the corresponding groups of DC / DC units; And An energy supply unit, the energy supply unit being connected to the output end of the three-level DC / DC parallel system; When any of the DC / DC units has a short-circuit fault, all of the DC / DC units are driven to block; The isolation module located in the faulty group disconnects the faulty DC / DC unit from the three-level DC / DC parallel system; During this process, the energy supply unit supplies energy to the load connected to the output end of the three-level DC / DC parallel system; After the faulty DC / DC unit is isolated, the remaining DC / DC units are unblocked and resume supplying energy to the load; The isolation module includes two isolation units; the two isolation units are respectively connected to the input side and the output side of the DC / DC unit; or, the two isolation units are both connected to the output side of the DC / DC unit; The isolation unit adopts any one of a fuse, a contactor, an electronic switch, and a diode; When the isolation unit adopts a fuse, the isolation module further includes an auxiliary fusing unit; the auxiliary fusing unit is adapted to form a fusing circuit with the fuse; when the DC / DC unit fails, the fusing circuit is adapted to accelerate the fusing of the fuse located in the faulty group.

2. The three-level DC / DC fault isolation system according to claim 1, characterized in that: The three-level DC / DC parallel system is an N + n redundant system; where N represents the number of normally operating DC / DC units, and n represents the number of standby DC / DC units.

3. The three-level DC / DC fault isolation system according to claim 2, characterized in that: When the isolation unit adopts a fuse, the value of N is greater than 6.

4. The three-level DC / DC fault isolation system according to claim 1, characterized in that: When the three-level DC / DC parallel system is operating normally, the energy supply unit is adapted to store energy through the output end of the three-level DC / DC parallel system.

5. The three-level DC / DC fault isolation system according to claim 4, characterized in that: The energy supply unit includes a battery pack or a supercapacitor bank; the battery pack or the supercapacitor bank is adapted to be directly connected to the output end of the three-level DC / DC parallel system.

6. The three-level DC / DC fault isolation system according to claim 4, characterized in that: The energy supply unit includes a bidirectional DC / DC unit and a battery pack or a supercapacitor bank; the battery pack or the supercapacitor bank is adapted to be connected to the output end of the three-level DC / DC parallel system through the bidirectional DC / DC unit.

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