Electronic DC circuit breaker based on DC voltage bidirectional DC / DC conversion

Abstract

The invention discloses an electronic DC circuit breaker based on DC voltage bidirectional DC / DC conversion, comprising two DC voltage bidirectional DC / DC conversion circuits with completely identical structural parameters and mirror-symmetrical settings, which are connected together through two inductors. The core of the DC voltage bidirectional DC / DC conversion circuit is two equivalent capacitors arranged in series and four IGBTs of the same specification arranged in series, the two equivalent capacitors in series are connected in parallel with the four IGBTs in series, and the middle point of the two equivalent capacitors is connected to the middle point of the four IGBT series branches; in the two DC voltage bidirectional DC / DC conversion circuits, the respective four IGBTs are controlled by several appropriate driving methods, so that the electronic DC circuit breaker can realize parallel operation and short-circuit protection of two sections of DC busbars with equal connection voltages, parallel operation and short-circuit protection of two sections of DC busbars with unequal connection voltages, and power supply and short-circuit protection from the active DC busbar to the passive DC busbar.

Description

Technical Field

[0001] The present invention relates to an electronic DC circuit breaker, and in particular to an electronic DC circuit breaker which can connect two sections of DC busbars with equal voltages or two sections of DC busbars with unequal voltages in a DC system, and can perform rapid disconnection protection when any section of the DC busbar fails. Background Art

[0002] DC systems are widely used in power plants, substations and other occasions where DC equipment is used, especially in rail transit locomotives and hybrid and pure battery-powered ships.

[0003] DC systems have many advantages over AC systems.

[0004] In terms of system control, the DC system is relatively simple. For example, the DC power supply and distribution system is only affected by the voltage amplitude, and only one physical quantity, the voltage amplitude, needs to be controlled. The AC system is relatively complex. For example, the AC power supply and distribution system is affected by the frequency, phase and voltage amplitude at the same time.

[0005] In terms of power transmission and transfer, the DC system has smaller losses, higher efficiency, better power quality, and is easier to interconnect distributed power sources. The reactive power, skin effect, line loss, etc. of the AC system have many negative effects on AC power transmission and distribution. Therefore, with the help of modern power electronics technology, high-voltage DC transmission projects and DC system power supply and distribution have become hot topics.

[0006] When designing a DC power supply and distribution system, in order to ensure the reliability of power supply, some important electrical equipment is powered by independent power supplies (such as batteries or rectifier power output). For example, one independent DC power supply supplies power to one or a group of equipment, and another independent DC power supply supplies power to another or another group of equipment. The failure of one power supply only affects the equipment it carries. The distribution buses of these two DC power supplies are usually called bus 1 and bus 2.

[0007] In order to further improve the reliability of equipment power supply, the two sections of DC bus 1 and 2 are connected through a DC circuit breaker, so that the two sections of DC bus 1 and 2 run in parallel. When a DC power supply fails, it is disconnected from the section of bus it is connected to, and the equipment it powers continues to be powered by another section of bus through "bus coupling". When a problem occurs in the equipment on a section of bus, causing a short circuit fault in the section of bus, the DC circuit breaker connecting the two sections of DC bus 1 and 2 is immediately disconnected, separating the faulty DC bus from the normal DC bus to avoid the expansion of the fault.

[0008] Therefore, on the one hand, the DC circuit breaker connecting the two sections of DC bus 1 and 2 must have sufficient capacity to meet the capacity requirements of the equipment carried by the faulty power supply when a power supply fails. On the other hand, the DC circuit breaker connecting the two sections of DC bus 1 and 2 must have a fast disconnection characteristic to quickly disconnect a section of the bus when a short circuit occurs, so as not to affect the normal operation of the equipment on the bus.

[0009] AC current has periodic zero crossings, which makes it easy to disconnect AC circuits with load. However, since DC current has no zero crossings, the load disconnection of DC circuits is not as good as that of AC circuits. When a section of the DC bus is short-circuited, the current flowing through the DC circuit breaker increases sharply, making it more difficult to disconnect overloaded DC current. Once the disconnection fails, it will have catastrophic consequences.

[0010] Existing mechanical contact DC circuit breakers are bulky, have slow switching action, and take hundreds of milliseconds to operate. When breaking the short-circuit current, the current may have reached its peak, making it very difficult to extinguish the arc. In addition, this type of DC circuit breaker can only connect two sections of DC bus with equal voltage values. If two sections of DC bus with unequal voltages need to be connected and run in parallel, this type of DC circuit breaker will be powerless. Therefore, the development of contactless electronic DC circuit breakers has become inevitable. Summary of the invention

[0011] In view of the problems existing in the prior art, the present invention discloses an electronic DC circuit breaker based on DC voltage bidirectional DC / DC conversion, comprising two DC voltage bidirectional DC / DC conversion circuits I and II having completely identical structural parameters and mirror-symmetrically arranged;

[0012] The DC voltage bidirectional DC / DC conversion circuit I includes a first fuse connected to the positive (+) end of the high voltage side and a second fuse connected to the negative (-) end of the high voltage side, an equivalent capacitor I and an equivalent capacitor II arranged in series, and four first IGBTs, second IGBTs, third IGBTs and fourth IGBTs of the same specification arranged in series;

[0013] The equivalent capacitor I and the equivalent capacitor II are connected in parallel with the first IGBT, the second IGBT, the third IGBT and the fourth IGBT which are arranged in series, and then connected in series with the first fuse and the second fuse; wherein the middle point of the equivalent capacitor I and the equivalent capacitor II is connected to the middle point of the four IGBT series branches;

[0014] The positive (+) terminal of the low voltage side output of the DC voltage bidirectional DC / DC conversion circuit I is connected to the connection point of the first IGBT and the second IGBT, and the negative (-) terminal of the DC voltage bidirectional DC / DC conversion circuit I is connected to the connection point of the third IGBT and the fourth IGBT;

[0015] The direct current voltage bidirectional DC / DC conversion circuit II includes a third fuse connected to the positive (+) end of the high voltage side and a fourth fuse connected to the negative (-) end of the high voltage side, an equivalent capacitor III and an equivalent capacitor IV arranged in series, and four fifth IGBTs, sixth IGBTs, seventh IGBTs, and eighth IGBTs of the same specification arranged in series; the equivalent capacitors III and IV arranged in series are connected in parallel with the four fifth IGBTs, sixth IGBTs, seventh IGBTs, and eighth IGBTs connected in series, and then connected in series with the third fuse and the fourth fuse; wherein the middle point of the equivalent capacitors III and IV is connected to the middle point of the series branch of the fifth IGBT, the sixth IGBT, the seventh IGBT, and the eighth IGBT;

[0016] The positive (+) terminal of the low voltage side output of the DC voltage bidirectional DC / DC conversion circuit II is connected to the connection point of the fifth IGBT and the sixth IGBT, and the negative (-) terminal of the low voltage side of the DC voltage bidirectional DC / DC conversion circuit II is connected to the connection point of the seventh IGBT and the eighth IGBT.

[0017] The low voltage side output positive (+) terminal of the DC voltage bidirectional DC / DC conversion circuit I is connected to the low voltage side output positive (+) terminal of the DC voltage bidirectional DC / DC conversion circuit II through a first filter inductor, and the low voltage side negative (-) terminal of the DC voltage bidirectional DC / DC conversion circuit I is connected to the low voltage side negative (-) terminal of the DC voltage bidirectional DC / DC conversion circuit II through a second filter inductor; the first filter inductor and the second filter inductor have the same parameters and are coupled through the same iron core magnetic circuit; a first current sensor CT1 is arranged on the branch of the first filter inductor, and a second current sensor CT2 is arranged on the branch of the second filter inductor.

[0018] Furthermore, the first IGBT and the fourth IGBT are controlled to be continuously turned on, the second IGBT and the third IGBT are controlled to be continuously turned off, the fifth IGBT and the eighth IGBT are controlled to be continuously turned on, and the sixth IGBT and the seventh IGBT are controlled to be continuously turned off, so as to perform bus short-circuit protection while two sections of DC bus with equal voltage Ud1=Ud2 connected on the P11, N11 terminal side and the P21, N21 terminal side of the electronic DC circuit breaker are operated in parallel.

[0019] Control the first IGBT and the fourth IGBT to be turned on according to PWM, control the second IGBT and the third IGBT to be continuously turned off, and control the fifth IGBT, the sixth IGBT, the seventh IGBT, and the eighth IGBT to be continuously turned off, so as to connect a DC bus with a higher voltage to the P11 and N11 terminal sides of the electronic DC circuit breaker, and connect a DC bus with a lower voltage to the P21 and N21 terminal sides, so as to realize parallel operation of two sections of DC buses with unequal voltages Ud1>Ud2, and the current flows from the DC bus with a higher voltage to the DC bus with a lower voltage, and at the same time perform bus short-circuit protection;

[0020] The second IGBT and the third IGBT are controlled to be turned on according to PWM, the first IGBT and the fourth IGBT are controlled to be continuously turned off, the fifth IGBT and the eighth IGBT are controlled to be continuously turned on, and the sixth IGBT and the seventh IGBT are controlled to be continuously turned off, so as to connect a DC bus with a higher voltage to the P11 and N11 terminal sides of the electronic DC circuit breaker, and connect a DC bus with a lower voltage to the P21 and N21 terminal sides, so as to realize parallel operation of two DC buses with unequal voltages Ud1>Ud2, and the current flows from the DC bus with a low voltage to the DC bus with a high voltage, and at the same time perform bus short-circuit protection.

[0021] The first IGBT and the fourth IGBT are controlled to be continuously turned on, the second IGBT and the third IGBT are controlled to be continuously turned off, the fifth IGBT and the eighth IGBT are controlled to be continuously turned on, and the sixth IGBT and the seventh IGBT are controlled to be continuously turned off, so as to connect an active DC bus at one end of the electronic DC circuit breaker, connect a passive DC bus at the other end of the electronic DC circuit breaker, distribute power from the active DC bus to the passive DC bus, and perform bus short-circuit protection at the same time.

[0022] Due to the adoption of the above technical scheme, the present invention provides an electronic DC circuit breaker based on DC voltage bidirectional DC / DC conversion. This circuit can realize the parallel operation and rapid protection of two sections of DC busbars with equal voltages, and can also realize the voltage matching parallel operation and rapid protection of two sections of DC busbars with unequal voltages. It is also possible to use this electronic DC circuit breaker to realize power supply and rapid protection of a passive DC busbar that temporarily loses power from an active DC busbar, thereby realizing mutual backup and fault protection of the dual buses of the DC system. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0024] Figure 1 : Schematic diagram of the electronic DC circuit breaker

[0025] Figure 2 : One of the current paths when the electronic DC circuit breaker connects two DC buses with equal voltage

[0026] Figure 3 : Another current path when the electronic DC circuit breaker connects two DC buses with equal voltage

[0027] Figure 4 : Schematic diagram of the current path of the electronic DC circuit breaker during the high level of the PWM drive signals of the gates of IGBTs V11 and V14

[0028] Figure 5 : Schematic diagram of the current path of the electronic DC circuit breaker during the low level of the PWM drive signals of the gates of IGBTs V11 and V14

[0029] Figure 6 : Schematic diagram of the current path of the electronic DC circuit breaker during the high level of the PWM drive signals of the gates of IGBTs V22 and V23

[0030] Figure 7 : Schematic diagram of the current path of the electronic DC circuit breaker during the low level of the PWM drive signals of the gates of IGBTs V22 and V23

[0031] Figure 8 : Schematic diagram of the short - circuit of two DC buses when the electronic DC circuit breaker connects two DC buses with equal voltage

[0032] Fig. 9 : Schematic diagram of the short - circuit of one DC bus when the electronic DC circuit breaker connects two DC buses with equal voltage

[0033] Fig.10 : Schematic diagram of the short - circuit of two DC buses when the electronic DC circuit breaker connects two DC buses with unequal voltage and Ud1 > Ud2

[0034] Fig.11 : Schematic diagram of the short - circuit of two DC buses when the electronic DC circuit breaker connects two DC buses with unequal voltage and Ud1 < Ud2 Detailed implementation mode

[0035] To make the technical solutions and advantages of the present invention clearer, the following clearly and completely describes the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention:

[0036] Such as Figure 1An electronic DC circuit breaker based on DC voltage bidirectional DC / DC conversion is shown, which specifically includes two DC voltage bidirectional DC / DC conversion circuits I 1 and II 2 which have completely the same structural parameters and are arranged in mirror symmetry;

[0037] The direct current voltage bidirectional DC / DC conversion circuit I1 includes a first fuse F11 connected to the positive (+) terminal P11 on the high voltage side and a second fuse F12 connected to the negative (-) terminal N11 on the high voltage side, two equivalent capacitors arranged in series, namely, an equivalent capacitor I Cd11 and an equivalent capacitor II Cd12, and four first IGBT V11, second IGBT V12, third IGBT V13 and fourth IGBT V14 of the same specification arranged in series, wherein the two equivalent capacitors in series, namely, the equivalent capacitor I Cd11 and the equivalent capacitor II Cd12, are connected in parallel with the four first IGBT V11, second IGBT V12, third IGBT V13 and fourth IGBT V141 arranged in series, and then connected in series with two fuses, namely, the first fuse F11 and the second fuse F12, wherein the middle point of the equivalent capacitor I Cd11 and the equivalent capacitor II Cd12 is connected to the middle point of the four IGBT series branches.

[0038] The low voltage side output positive (+) terminal P12 of the DC voltage bidirectional DC / DC conversion circuit I1 is derived from the connection point of two IGBTs (the first IGBT V11 and the second IGBT V12), that is, the e terminal of V11 and the c terminal of V12, and the negative (-) terminal N12 is derived from the connection point of two IGBTs (the third IGBT V13 and the fourth IGBT V14), that is, the e terminal of V13 (also the c terminal of V14).

[0039] The direct current voltage bidirectional DC / DC conversion circuit II 2 includes a third fuse F21 connected to the positive (+) terminal P21 on the high voltage side, a fourth fuse F22 connected to the negative (-) terminal N21 on the high voltage side, two equivalent capacitors arranged in series, namely, an equivalent capacitor III Cd21 and an equivalent capacitor IV Cd22, and four IGBTs of the same specification arranged in series (namely, a fifth IGBT V21, a sixth IGBT V22, a seventh IGBT V23, and an eighth IGBT V24), wherein the two equivalent capacitors in series are connected in parallel with the four IGBTs in series (V21, V22, V23, and V24), and then connected in series with the third fuse F21 and the fourth fuse F22, and the middle point of the equivalent capacitor III Cd21 and the equivalent capacitor IV Cd22 is connected to the middle point of the series branches of the four IGBTs (namely, V21, V22, V23, and V24);

[0040] The low voltage side output positive (+) terminal P22 of the direct current voltage bidirectional DC / DC conversion circuit II 2 is derived from the connection point of two IGBTs (fifth IGBT V21 and sixth IGBT V22), namely, the e terminal of V21 (also the c terminal of V22), and the negative (-) terminal N22 is derived from the connection point of two IGBTs (seventh IGBT V23 and eighth IGBT V24), namely, the e terminal of V23 (also the c terminal of V24);

[0041] Furthermore, the low voltage side output positive (+) terminal P12 of the DC voltage bidirectional DC / DC conversion circuit I1 is connected to the low voltage side output positive (+) terminal P22 of the DC voltage bidirectional DC / DC conversion circuit II 2 through a first filter inductor Ld1, and the low voltage side negative (-) terminal N12 of the DC voltage bidirectional DC / DC conversion circuit I1 is connected to the low voltage side negative (-) terminal N22 of the DC voltage bidirectional DC / DC conversion circuit II 2 through a second filter inductor Ld2; the first filter inductor Ld1 and the second filter inductor Ld2 have the same parameters and are coupled through the same iron core magnetic circuit, and a first current sensor CT1 is set on the branch of the first filter inductor Ld1, and a second current sensor CT2 is set on the branch of the second filter inductor Ld2.

[0042] This circuit has the following working modes:

[0043] 1. Electronic DC circuit breaker connects two DC busbars with equal voltage for parallel operation and short circuit protection

[0044] In the DC voltage bidirectional DC / DC conversion circuit I1, a continuous high level is applied to the gates of the first IGBT V11 and the fourth IGBT V14 to make them continuously turned on, and a continuous low level is applied to the gates of the second IGBT V12 and the third IGBT V13 to make them continuously turned off. In the DC voltage bidirectional DC / DC conversion circuit II 2, a continuous high level is applied to the gates of the fifth IGBT V21 and the eighth IGBT V24 to make them continuously turned on, and a continuous low level is applied to the gates of the sixth IGBT V22 and the seventh IGBT V23 to make them continuously turned off. Two sections of DC busbars with the same voltage (Ud1=Ud2) are connected to the P11, N11 terminal side and the P21, N21 terminal side of the electronic DC circuit breaker and operate in parallel.

[0045] (1) When the load of the two DC bus sections is heavy, the current between the two bus sections flows from bus section 1 to bus section 2. Figure 2As shown, the positive current flows in from P11, passes through the first fuse F11, the first IGBT V11, the first filter inductor Ld1, the freewheeling diode of the second IGBT V12, and the third fuse F21, and flows out from P21; the negative current flows in from N21, passes through the fourth fuse F22, the freewheeling diode of the eighth IGBT V24, the second filter inductor Ld2, the fourth IGBT V14, and the second fuse F12, and flows out from N11.

[0046] When two DC busbars are short-circuited, Figure 8 As shown, the voltage of the two DC busbars drops, and the current flows from the first DC busbar connection terminal P11 (+) through the first fuse F11, the first IGBT V11, the first filter inductor Ld1, the freewheeling diode of the fifth IGBT V21, the third fuse F21, the short-circuit point, the fourth fuse F22, the freewheeling diode of the eighth IGBT V24, the second filter inductor Ld2, the fourth IGBT V14, and the second fuse F12 to the first DC busbar connection terminal N11 (-). The current monitored by the current sensors CT1 and CT2 set in the inductor branch increases rapidly from the normal working current before the short-circuit fault occurs at a certain load rate current limit. After about 100-150uS (about 2-3 times the rated current), the first IGBT V11, the fourth IGBTV14, the fifth IGBT V21, and the eighth IGBT V24 are all turned off, blocking the connection between the DC buses 1 and 2, and realizing short-circuit fault isolation protection.

[0047] (2) When the load of one DC bus is heavy, the current between the two bus sections flows from bus section 2 to bus section 1. Figure 3 As shown, the positive current flows in from P21, passes through the third fuse F21, the fifth IGBT V21, the first filter inductor Ld1, the freewheeling diode of the first IGBT V11, and the first fuse F11, and flows out from P11; the negative current flows in from N11, passes through the second fuse F12, the freewheeling diode of the fourth IGBT V14, the second filter inductor Ld2, the eighth IGBT V24, and the fourth fuse F22, and flows out from N21;

[0048] When a DC bus short circuit occurs, Fig. 9As shown, the voltage of the 1st DC bus drops, and the current flows from the 2nd DC bus connection terminal P21 (+) in sequence through the third fuse F21, the fifth IGBT V21, the first filter inductor Ld1, the freewheeling diode of the first IGBT V11, the first fuse F11, the short-circuit point, the second fuse F12, the freewheeling diode of the fourth IGBT V14, the second filter inductor Ld2, the eighth IGBT V24, and the fourth fuse F22 into the 2nd DC bus connection terminal N21 (-). The current monitored by the current sensors CT1 and CT2 set in the inductor branch increases rapidly from the normal working current before the short-circuit fault occurs at a certain load rate current limit. After about 100-150uS (about 2-3 times the rated current), the first IGBT V11, the fourth IGBTV14, the fifth IGBT V21, and the eighth IGBT V24 are all turned off, blocking the connection between the DC buses 1 and 2, and realizing short-circuit fault isolation protection.

[0049] 2. Electronic DC circuit breaker connects two DC busbars with unequal voltages for parallel operation and short-circuit protection

[0050] (1) Current flows from the DC bus with higher voltage to the DC bus with lower voltage

[0051] In the DC voltage bidirectional DC / DC conversion circuit I1, the first IGBT V11 and the fourth IGBT V14 are controlled to be turned on according to PWM, and the second IGBT V12 and the third IGBT V13 are continuously turned off. In the DC voltage bidirectional DC / DC conversion circuit II 2, the fifth IGBT V21, the sixth IGBT V22, the seventh IGBT V23 and the eighth IGBT V24 are controlled to be continuously turned off. A DC bus with a higher voltage is connected to the P11 and N11 terminal sides of the electronic DC circuit breaker, and a DC bus with a lower voltage is connected to the P21 and N21 terminal sides of the electronic DC circuit breaker, so that two sections of DC buses with unequal voltages (Ud1>Ud2) run in parallel. In this control method, the current flows from the DC bus with a higher voltage to the DC bus with a lower voltage.

[0052] The PWM drive signal applied to the gates of the first IGBT V11 and the fourth IGBT V14 has a path of the current in the electronic DC circuit breaker during the high level period. Figure 4 As shown, the positive current flows in from P11, passes through the first fuse F11, the first IGBT V11, the first filter inductor Ld1, the freewheeling diode of the fifth IGBT V21, and the third fuse F21, and flows out from P21; the negative current flows in from N21, passes through the fourth fuse F22, the freewheeling diode of the eighth IGBT V24, the second filter inductor Ld2, the fourth IGBTV14, and the second fuse F12 and flows out from N11;

[0053] The path of the current in the electronic DC circuit breaker during the low level period of the PWM drive signal applied to the gate of the first IGBT V11 and the fourth IGBT V14 is as follows: Figure 5 As shown, the role of inductive energy storage maintains the path of current, which flows in from N21, passes through the fourth fuse F22, the eighth IGBT V24 freewheeling diode, the second filter inductor Ld2, the third IGBT V13 freewheeling diode, the second IGBT V12 freewheeling diode, the first filter inductor Ld1, the fifth IGBT V21 freewheeling diode, the third fuse F21, and flows out from P21;

[0054] When two DC busbars are short-circuited, Fig.10 As shown, the voltage of the two DC busbars drops, and the current flows from the first DC busbar connection terminal P11 (+) through the first fuse F11, the first IGBT V11, the first filter inductor Ld1, the freewheeling diode of the fifth IGBT V21, the third fuse F21, the short-circuit point, the fourth fuse F22, the freewheeling diode of the eighth IGBT V24, the second filter inductor Ld2, the fourth IGBT V14, and the second fuse F12 to the first DC busbar connection terminal N11 (-). The current monitored by the current sensors CT1 and CT2 set in the inductor branch increases rapidly from the normal working current before the short-circuit fault occurs at a certain load rate current limit. After about 100-150uS (about 2-3 times the rated current), the first IGBT V11 and the fourth IGBTV14 are turned off, blocking the connection between the DC buses 1 and 2, and realizing short-circuit fault isolation protection.

[0055] (2) Current flows from the DC bus with lower voltage to the DC bus with higher voltage

[0056] In a DC voltage bidirectional DC / DC conversion circuit (1), the first IGBT V11 and the fourth IGBT V14 are controlled to be continuously turned on, and the second IGBT V12 and the third IGBT V13 are controlled to be continuously turned off. In a DC voltage bidirectional DC / DC conversion circuit (2), the sixth IGBT V22 and the seventh IGBT V23 are controlled to be turned on according to PWM, and the fifth IGBT V21 and the eighth IGBT V24 are controlled to be continuously turned off. A DC bus with a lower voltage is connected to the P11 and N11 terminal sides of the electronic DC circuit breaker, and a DC bus with a higher voltage is connected to the P21 and N21 terminal sides of the electronic DC circuit breaker, so that two sections of DC buses with unequal voltages (Ud1<Ud2) are operated in parallel. In this control mode, current flows from the DC bus with a lower voltage to the DC bus with a higher voltage.

[0057] The PWM drive signal applied to the gate of the sixth IGBT V22 and the seventh IGBT V23, during the high level period, the path of the current in the electronic DC circuit breaker is as follows: Figure 6As shown, the current flows in from P11, passes through the first fuse F11, the first IGBT V11, the first filter inductor Ld1, the sixth IGBT V22, the seventh IGBT V23, the second filter inductor Ld2, the fourth IGBT V14, the second fuse F12, and flows out from N11;

[0058] The PWM drive signal applied to the gate of the sixth IGBT V22 and the seventh IGBT V23, during the low level period, the path of the current in the electronic DC circuit breaker is as follows: Figure 7 As shown, the positive current flows in from P11, passes through the first fuse F11, the first IGBT V11, the first filter inductor Ld1, the freewheeling diode of the fifth IGBT V21, and the third fuse F21, and flows out from P21; the negative current flows in from N21, passes through the fourth fuse F22, the freewheeling diode of the eighth IGBT V24, the second filter inductor Ld2, the fourth IGBTV14, and the second fuse F12 and flows out from N11.

[0059] When two DC busbars are short-circuited, Fig.11 As shown, the voltage of the two DC busbars drops, and the current flows from the first DC busbar connection terminal P11 (+) through the first fuse F11, the first IGBT V11, the first filter inductor Ld1, the freewheeling diode of the fifth IGBT V21, the third fuse F21, the short-circuit point, the fourth fuse F22, the freewheeling diode of the eighth IGBT V24, the second filter inductor Ld2, the fourth IGBT V14, and the second fuse F12 to the first DC busbar connection terminal N11 (-). The current monitored by the current sensors CT1 and CT2 set in the inductor branch increases rapidly from the normal working current before the short-circuit fault occurs at a certain load rate current limit. After about 100-150uS (about 2-3 times the rated current), the first IGBT V11 and the fourth IGBTV14 are turned off, and the sixth IGBT V22 and the seventh IGBT V23 are turned off, blocking the connection between the DC busbars 1 and 2, and realizing short-circuit fault isolation protection.

[0060] 3. Connect active DC bus and passive DC bus for parallel operation and short circuit protection

[0061] In the DC voltage bidirectional DC / DC conversion circuit I1, a continuous high level is applied to the gates of the first IGBT V11 and the fourth IGBT V14 to keep them turned on, and a continuous low level is applied to the gates of the second IGBT V12 and the third IGBT V13 to keep them turned off. In the DC voltage bidirectional DC / DC conversion circuit II 2, a continuous high level is applied to the gates of the fifth IGBT V21 and the eighth IGBT V24 to keep them turned on, and a continuous low level is applied to the gates of the sixth IGBT V22 and the seventh IGBT V23 to keep them turned off.

[0062] (1) The P11 and N11 terminals of the electronic DC circuit breaker are connected to the active DC bus, and the P21 and N21 terminals are connected to the passive DC bus to achieve power distribution from one DC bus to two DC buses. The current path is as follows: Figure 2 shown.

[0063] When two DC busbars are short-circuited, Figure 8 As shown, the voltage of the two DC busbars drops, and the current flows from the first DC busbar connection terminal P11 (+) through the first fuse F11, the first IGBT V11, the first filter inductor Ld1, the freewheeling diode of the fifth IGBT V21, the third fuse F21, the short-circuit point, the fourth fuse F22, the freewheeling diode of the eighth IGBT V24, the second filter inductor Ld2, the fourth IGBT V14, and the second fuse F12 to the first DC busbar connection terminal N11 (-). The current monitored by the current sensors CT1 and CT2 set in the inductor branch increases rapidly from the normal working current before the short-circuit fault occurs at a certain load rate current limit. After about 100-150uS (about 2-3 times the rated current), the first IGBT V11 and the fourth IGBTV14 are turned off, and the fifth IGBT V21 and the eighth IGBT V24 are turned off, blocking the connection between the DC busbars 1 and 2, and realizing short-circuit fault isolation protection.

[0064] (2) The P21 and N21 terminals of the electronic DC circuit breaker are connected to the active DC bus, and the P11 and N11 terminals are connected to the passive DC bus, so that two DC buses can supply power to one DC bus. The current path is as follows: Figure 3 shown.

[0065] When a DC bus short circuit occurs, Fig. 9 As shown, the voltage of the first DC bus drops, and the current flows from the second DC bus connection terminal P21 (+) in sequence through the third fuse F21, the fifth IGBT V21, the first filter inductor Ld1, the freewheeling diode of the first IGBT V11, the first fuse F11, the short-circuit point, the second fuse F12, the freewheeling diode of the fourth IGBT V14, the second filter inductor Ld2, the eighth IGBT V24, the fourth fuse F22, and flows into the second DC bus connection terminal N21 (-). The current monitored by the current sensors CT1 and CT2 set in the inductor branch increases rapidly from the normal working current before the short-circuit fault occurs at a certain load rate current limit. After about 100-150uS (about 2-3 times the rated current), the first IGBT V11, the fourth IGBTV14, the fifth IGBT V21, and the eighth IGBT V24 are all turned off, blocking the connection between the DC buses 1 and 2, and realizing short-circuit fault isolation protection.

[0066] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. An electronic DC circuit breaker based on DC voltage bidirectional DC / DC conversion, characterized in that It includes two DC voltage bidirectional DC / DC conversion circuits I (1) and II (2) which have completely the same structural parameters and are arranged in mirror symmetry; The direct current voltage bidirectional DC / DC conversion circuit I (1) comprises a first fuse (F11) connected to a positive (+) terminal (P11) on a high voltage side thereof and a second fuse (F12) connected to a negative (-) terminal (N11) on a high voltage side thereof, an equivalent capacitor I (Cd11) and an equivalent capacitor II (Cd12) arranged in series, and four first IGBTs (V11), second IGBTs (V12), third IGBTs (V13) and fourth IGBTs (V14) of the same specification arranged in series; The equivalent capacitor I (Cd11) and the equivalent capacitor II (Cd12) are connected in parallel with the first IGBT (V11), the second IGBT (V12), the third IGBT (V13) and the fourth IGBT (V14) which are arranged in series, and then connected in series with the first fuse (F11) and the second fuse (F12); wherein the middle point of the equivalent capacitor I (Cd11) and the equivalent capacitor II (Cd12) is connected to the middle point of the above four IGBT series branches; The low voltage side output positive (+) terminal (P12) of the DC voltage bidirectional DC / DC conversion circuit I (1) is connected to the connection point of the first IGBT (V11) and the second IGBT (V12), and the low voltage side negative (-) terminal (N12) of the DC voltage bidirectional DC / DC conversion circuit I (1) is connected to the connection point of the third IGBT (V13) and the fourth IGBT (V14); The DC voltage bidirectional DC / DC conversion circuit II (2) comprises a third fuse (F21) connected to the positive (+) terminal (P21) of the high voltage side and a fourth fuse (F22) connected to the negative (-) terminal (N21) of the high voltage side, an equivalent capacitor III (Cd21) and an equivalent capacitor IV (Cd22) arranged in series, and four fifth IGBTs (V21), sixth IGBTs (V22), seventh IGBTs (V23) and eighth IGBTs (V24) of the same specification arranged in series; the equivalent capacitors III (Cd21) and equivalent capacitors IV (Cd22) arranged in series are connected in parallel with the four fifth IGBTs (V21), sixth IGBTs (V22), seventh IGBTs (V23) and eighth IGBTs (V24) connected in series, and then connected in series with the third fuse (F21) and the fourth fuse (F22); wherein the middle point of the equivalent capacitors III (Cd21) and the equivalent capacitors IV (Cd22) and the fifth IGBT (V21), the sixth IGBT (V22), the seventh IGBT (V23), and the eighth IGBT (V24) are connected to the middle point of the series branch; The low voltage side output positive (+) terminal (P22) of the DC voltage bidirectional DC / DC conversion circuit II (2) is connected to the connection point of the fifth IGBT (V21) and the sixth IGBT (V22), and the low voltage side negative (-) terminal (N22) of the DC voltage bidirectional DC / DC conversion circuit II (2) is connected to the connection point of the seventh IGBT (V23) and the eighth IGBT (V24); Controlling the first IGBT (V11) and the fourth IGBT (V14) to be continuously turned on, controlling the second IGBT (V12) and the third IGBT (V13) to be continuously turned off, controlling the fifth IGBT (V21) and the eighth IGBT (V24) to be continuously turned on, and controlling the sixth IGBT (V22) and the seventh IGBT (V23) to be continuously turned off, so as to connect the high voltage side positive (+) terminal (P11) and the high voltage side negative (-) terminal (N11) of the DC voltage bidirectional DC / DC conversion circuit I (1) and the high voltage side positive (+) terminal (P21) and the high voltage side negative (-) terminal (N21) of the DC voltage bidirectional DC / DC conversion circuit II (2) to two sections of DC buses with equal voltages and operate in parallel while performing bus short circuit protection; Controlling the first IGBT (V11) and the fourth IGBT (V14) to be turned on according to PWM, controlling the second IGBT (V12) and the third IGBT (V13) to be continuously turned off, and controlling the fifth IGBT (V21), the sixth IGBT (V22), the seventh IGBT (V23), and the eighth IGBT (V24) to be continuously turned off, so as to connect a DC bus with a higher voltage to the positive (+) terminal (P11) on the high voltage side and the negative (-) terminal (N11) on the high voltage side of the DC voltage bidirectional DC / DC conversion circuit I (1), and to connect a DC bus with a lower voltage to the positive (+) terminal (P21) on the high voltage side and the negative (-) terminal (N21) on the high voltage side of the DC voltage bidirectional DC / DC conversion circuit II (2), so as to realize parallel operation of two sections of DC buses with unequal voltages (Ud1>Ud2), so that current flows from the DC bus with a higher voltage to the DC bus with a lower voltage, and at the same time, bus short-circuit protection is performed; Controlling the second IGBT (V12) and the third IGBT (V13) to be turned on according to PWM, controlling the first IGBT (V11) and the fourth IGBT (V14) to be continuously turned off, controlling the fifth IGBT (V21) and the eighth IGBT (V24) to be continuously turned on, and controlling the sixth IGBT (V22) and the seventh IGBT (V23) to be continuously turned off, so as to connect a DC bus with a higher voltage to the positive (+) terminal (P11) on the high voltage side and the negative (-) terminal (N11) on the high voltage side of the DC voltage bidirectional DC / DC conversion circuit I (1), and to connect a DC bus with a lower voltage to the positive (+) terminal (P21) on the high voltage side and the negative (-) terminal (N21) on the high voltage side of the DC voltage bidirectional DC / DC conversion circuit II (2), so as to realize parallel operation of two sections of DC buses with unequal voltages, so that current flows from the DC bus with a lower voltage to the DC bus with a higher voltage, and at the same time, bus short-circuit protection is performed; The first IGBT (V11) and the fourth IGBT (V14) are controlled to be continuously turned on, the second IGBT (V12) and the third IGBT (V13) are controlled to be continuously turned off, the fifth IGBT (V21) and the eighth IGBT (V24) are controlled to be continuously turned on, and the sixth IGBT (V22) and the seventh IGBT (V23) are controlled to be continuously turned off, so as to connect an active DC bus at one end of the electronic DC circuit breaker, connect a passive DC bus at the other end of the electronic DC circuit breaker, distribute power from the active DC bus to the passive DC bus, and perform bus short-circuit protection at the same time.

2. The electronic DC circuit breaker based on DC voltage bidirectional DC / DC conversion according to claim 1 is further characterized by: The low voltage side output positive (+) terminal (P12) of the DC voltage bidirectional DC / DC conversion circuit I (1) is connected to the low voltage side output positive (+) terminal (P22) of the DC voltage bidirectional DC / DC conversion circuit II (2) through a first filter inductor (Ld1), and the low voltage side negative (-) terminal (N12) of the DC voltage bidirectional DC / DC conversion circuit I (1) is connected to the low voltage side negative (-) terminal (N22) of the DC voltage bidirectional DC / DC conversion circuit II (2) through a second filter inductor (Ld2); the first filter inductor (Ld1) and the second filter inductor (Ld2) have the same parameters and are coupled through the same iron core magnetic circuit; a first current sensor (CT1) is arranged on the branch of the first filter inductor (Ld1), and a second current sensor (CT2) is arranged on the branch of the second filter inductor (Ld2).

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