Bidirectional direct-current fault breaking device and control method thereof

Abstract

The invention discloses a bidirectional direct-current fault breaking device and a control method thereof, and relates to the field of power equipment, the bidirectional direct-current fault breaking device comprises a main loop unit which comprises a first switch, an inductor, a current transformer interface and a coupling transformer secondary winding which are sequentially connected in series; the voltage injection unit comprises a power supply module, a current conversion module and a coupling transformer secondary winding which are connected in sequence; the power supply module comprises a first capacitor and a second capacitor which are connected in series; the current conversion module can change the flow direction of current flowing through the primary winding of the coupling transformer; and the coupling transformer primary winding is matched with the coupling transformer secondary winding to form a coupling transformer. According to the invention, fault current can be suppressed to zero very quickly, the fault current can be modulated into low-amplitude and high-frequency ripple current, a zero-current and low-voltage action time window can be provided for an ultra-fast mechanical switch, and arc-free on-off of a direct-current fault is realized.

Description

Technical Field

[0001] The invention relates to the technical field of electric power equipment, in particular to a bidirectional direct current fault breaking device and a control method thereof. Background Art

[0002] In order to enable a large number of renewable energy sources to be connected to the power grid, the best solution is to develop a DC transmission and distribution network, which has the advantages of higher efficiency, higher flexibility, and longer transmission distance compared to the AC power grid. However, due to the low impedance of the DC transmission and distribution network, when a short circuit occurs in the DC system, the fault current will rise rapidly. If it cannot be removed in time, it will cause the converter station to lock, resulting in large-scale power outages and even significant economic losses.

[0003] Because of the low impedance of the DC system and the lack of natural zero crossing of the current, arc-free interruption of DC short-circuit faults becomes a huge challenge, so bidirectional DC fault interruption devices have great research value and practical prospects. At present, the research on bidirectional DC fault interruption devices can be divided into the following three categories: mechanical bidirectional DC fault interruption devices, all-solid-state bidirectional DC fault interruption devices and hybrid bidirectional DC fault interruption devices.

[0004] Mechanical bidirectional DC fault interrupters have the advantage of low loss, but have a slow response speed to short-circuit faults; all-solid-state bidirectional DC fault interrupters have a fast response speed to short-circuit faults, but have high conduction loss and high heat generation, and require expensive heat dissipation equipment;

[0005] The hybrid bidirectional DC fault interrupter combines the advantages of mechanical circuit breakers and all-solid-state bidirectional DC fault interrupters, but its response speed is still limited by the delay time of the mechanical switch;

[0006] The improved hybrid bidirectional DC fault interrupter adds a commutation switch (solid-state switch) in series with the mechanical switch in the main branch, which greatly improves the response speed to faults, but the conduction loss of the commutation switch cannot be ignored.

[0007] Conventional injection-type bidirectional DC fault interrupters only create a current zero-crossing point in the main circuit, and the action delay time of the main switch needs to be considered to make the main switch and the current zero-crossing point accurately match, so the control of the main switch is difficult and difficult to achieve. Moreover, the current research on bidirectional DC fault interrupters can usually only interrupt unidirectional faults, and cannot achieve arc-free interruption of bidirectional faults. Summary of the invention

[0008] In order to solve the above problems, the present invention provides an active injection bidirectional DC fault interrupter based on a full-bridge commutation structure and a control method thereof, which solves the problem of high control difficulty caused by the lack of a zero-crossing point of the fault current in the main circuit and the need for the main switch to accurately match the zero-crossing point of a single fault current in the prior art. The present invention has the advantages of low loss, fast response speed, low control difficulty, bidirectional fault response capability and energy recovery.

[0010] In view of the above problems existing in the prior art, the present invention is proposed.

[0011] Therefore, the problem to be solved by the present invention is that the prior art lacks a zero-crossing point for the fault current of the main circuit and the main switch needs to be precisely matched with a single zero-crossing point of the fault current, which results in high control difficulty.

[0012] In order to solve the above technical problems, one of the objects of the present invention is to provide a bidirectional DC fault interrupting device, which includes,.

[0013] As a preferred solution of the bidirectional DC fault interrupting device described in the present invention, wherein: a main circuit unit includes a first switch, an inductor, a current transformer interface and a secondary winding of a coupling transformer connected in series in sequence; a voltage injection unit includes a power module, a commutation module and a secondary winding of a coupling transformer connected in sequence; the power module includes a first capacitor and a second capacitor connected in series for outputting voltage; the commutation module can change the direction of current flowing through the primary winding of the coupling transformer; the primary winding of the coupling transformer cooperates with the secondary winding of the coupling transformer to form a coupling transformer.

[0014] As a preferred solution of the bidirectional DC fault interrupter device of the present invention, the power module further includes a first fully-controlled device and a second fully-controlled device, and the two are connected in series between the first capacitor and the second capacitor.

[0015] As a preferred solution of the bidirectional DC fault interrupting device described in the present invention, the power supply module also includes a first diode and a second diode, the cathode of the first diode is connected to the positive electrode of the second capacitor, and the positive electrode is connected to the negative electrode of the first capacitor; the cathode of the second diode is connected to the wire between the first fully-controlled device and the second fully-controlled device, and the positive electrode is respectively connected to the negative electrode of the first capacitor and the positive electrode of the first diode.

[0016] As a preferred solution of the bidirectional DC fault interrupter device of the present invention, the power module further includes a second switch, and the second switch short-circuits the second fully-controlled device.

[0017] As a preferred solution of the bidirectional DC fault interrupting device described in the present invention, wherein: the commutation module includes a third fully-controlled device and a fifth fully-controlled device, the first pole of the third fully-controlled device is connected to one end of the primary winding of the coupling transformer, and the second pole is connected to the positive pole of the second capacitor; the first pole of the fifth fully-controlled device is respectively connected to the positive pole of the first capacitor, the positive pole of the first diode and the positive pole of the second diode, and the second pole is connected to the other end of the primary winding of the coupling transformer.

[0018] As a preferred embodiment of the bidirectional DC fault interrupting device described in the present invention, the converter module further includes a fourth fully-controlled device and a sixth fully-controlled device, wherein the first pole of the fourth fully-controlled device is respectively connected to the positive pole of the first capacitor, the positive pole of the first diode and the positive pole of the second diode, and the second pole is connected to one end of the primary winding of the coupling transformer; the first pole of the sixth fully-controlled device is connected to the other end of the primary winding of the coupling transformer, and the second pole is connected to the positive pole of the second capacitor.

[0019] Another object of the present invention is to provide a control method for a bidirectional DC fault interrupting device, which is applicable to the above-mentioned bidirectional DC fault interrupting device, and the method includes: judging whether a fault occurs in the main circuit unit; if a fault occurs, starting a voltage injection unit to inject a reverse voltage into the main circuit unit and reducing the voltage in the main circuit unit to zero; regulating the voltage injection unit to inject a reverse voltage with an amplitude lower than the fault voltage into the main circuit unit so that the fault voltage rises; regulating the voltage injection unit to modulate the fault current into a ripple current; completing arc-free isolation of the main circuit unit; and recovering energy from the voltage injection unit.

[0020] As a preferred solution of the control method of the bidirectional DC fault interrupter device of the present invention, the fault includes a forward short circuit fault and a reverse short circuit fault.

[0021] As a preferred scheme of the control method of the bidirectional DC fault interrupter device of the present invention, the voltage injection unit includes a first capacitor and a second capacitor, the first capacitor and the second capacitor are discharged in series, and a reverse voltage is injected into the main circuit unit to reduce the voltage in the main circuit unit to zero.

[0022] As a preferred solution of the control method of the bidirectional DC fault interrupter device of the present invention, the method of causing the fault voltage to recover includes isolating the first capacitor and the second capacitor so that the second capacitor discharges alone.

[0023] The beneficial effects of the present invention are as follows: the present invention can work in the fault current rapid suppression stage, the multi-modal voltage injection stage and the arc suppression stage, and can achieve extremely fast suppression of the fault current to zero, can modulate the fault current into a low-amplitude and high-frequency ripple current, and can provide a zero-current and low-voltage action time window for an ultra-fast mechanical switch, thereby achieving arc-free interruption of a DC fault. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0025] Figure 1 It is a schematic diagram of the current structure of a bidirectional DC fault interrupter.

[0026] Figure 2 It is a circuit diagram of a bidirectional DC fault interrupter in standby mode.

[0027] Figure 3 The schematic diagram is a schematic diagram of a voltage injection unit entering a fast suppression stage when a forward fault occurs in a bidirectional DC fault interrupter.

[0028] Figure 4 It is a schematic diagram of the voltage injection unit entering the fast suppression stage when a reverse fault occurs in the bidirectional DC fault interrupter.

[0029] Figure 5 The schematic diagram is a schematic diagram of a voltage injection unit entering a voltage injection stage when a forward fault occurs in a bidirectional DC fault interrupter.

[0030] Figure 6 The schematic diagram is a schematic diagram of a voltage injection unit entering a voltage injection stage when a reverse fault occurs in a bidirectional DC fault interrupter.

[0031] Figure 7 The diagram is a schematic diagram of charging the second capacitor when a forward fault occurs in the bidirectional DC fault interrupter.

[0032] Figure 8 The present invention is a schematic diagram of charging the second capacitor and the first capacitor when a forward fault occurs in the bidirectional DC fault interrupter.

[0033] Fig. 9 The diagram is a schematic diagram of charging the second capacitor when a reverse fault occurs in the bidirectional DC fault interrupter.

[0034] Fig.10The present invention is a schematic diagram of charging the second capacitor and the first capacitor when a reverse fault occurs in the bidirectional DC fault interrupter.

[0035] Fig.11 It is the key waveform diagram of the bidirectional DC fault interrupter when a forward fault occurs.

[0036] Fig.12 It is the key waveform diagram of the bidirectional DC fault interrupter when a reverse fault occurs.

[0037] Fig.13 The figure is a flow chart of a control method of a bidirectional DC fault interrupter. DETAILED DESCRIPTION

[0038] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific embodiments of the present invention are described in detail below in conjunction with the accompanying drawings.

[0039] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein, and those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0040] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure or characteristic that may be included in at least one implementation of the present invention. The term "in one embodiment" that appears in different places in this specification does not necessarily refer to the same embodiment, nor is it an embodiment that is mutually exclusive with other embodiments, either individually or selectively.

[0041] Example 1

[0042] Reference Figure 1 , which is the first embodiment of the present invention, and provides a specific structure of a bidirectional DC fault interrupting device, the device comprising a main circuit unit 100 and a voltage injection unit 200.

[0043] Specifically, the main circuit unit 100 includes a first switch S1, an inductor L3, a current transformer interface MPO, and a coupling transformer secondary winding L2, which are connected in series from left to right. The first switch S1 is an ultra-fast mechanical switch, the inductor L3 is a line parasitic inductance, and the current transformer interface MPO is used to connect a current transformer.

[0044] The voltage injection unit 200 includes a power module 201, a commutation module 202 and a coupling transformer secondary winding L1. The power module 201 can provide voltage to the coupling transformer secondary winding L1, and the coupling transformer secondary winding L1 can also charge the power module 201. The commutation module 202 can change the direction of the voltage.

[0045] Preferably, the power module 201 includes a first capacitor C1, a second capacitor C2, a first fully-controlled device Q1, a second fully-controlled device Q2, a first diode D1, a second diode D2 and a second switch S2.

[0046] The first capacitor C1 and the second capacitor C2 are connected in series, and the first fully-controlled device Q1 and the second fully-controlled device Q2 are connected in series between the first capacitor C1 and the second capacitor C2, that is, between the positive electrode of the first capacitor C1 and the negative electrode of the second capacitor C2.

[0047] The cathode of the first diode D1 is connected to the anode of the second capacitor C2, and the cathode of the first diode D1 is connected to the cathode of the first capacitor C1.

[0048] The cathode of the second diode D2 is connected to the wire between the first fully-controlled device Q1 and the second fully-controlled device Q2, and the anode is connected to the cathode of the first capacitor C1 and the anode of the first diode D1.

[0049] The first diode D1 and the second diode D2 in the voltage injection unit 200 are used to prevent the capacitor from being short-circuited when the discharge path of the capacitor does not pass through the primary winding L1 of the coupling transformer.

[0050] The second switch S2 short-circuits the second diode D2 , that is, one end of the second switch S2 is connected to one end of the second diode D2 , and the other end of the second switch S2 is connected to the other end of the second diode D2 .

[0051] The commutation module 202 includes a third fully-controlled device Q3, a fourth fully-controlled device Q4, a fifth fully-controlled device Q5, and a sixth fully-controlled device Q6. The third fully-controlled device Q3 is connected in series with the sixth fully-controlled device Q6, and the fourth fully-controlled device Q4 is connected in series with the fifth fully-controlled device Q5. The device after the third fully-controlled device Q3 and the sixth fully-controlled device Q6 are connected in series is connected in parallel with the device after the fourth fully-controlled device Q4 and the fifth fully-controlled device Q5 are connected in series.

[0052] Further, a first pole of the third fully-controlled device Q3 is connected to the primary winding L1 of the coupling transformer, and a second pole is connected to a second pole of the sixth fully-controlled device Q6;

[0053] The second pole of the fourth fully-controlled device Q4 is connected to the primary winding L1 of the coupling transformer, and the first pole is connected to the first pole of the fifth fully-controlled device Q5;

[0054] The first pole of the sixth fully-controlled device Q6 is connected to the primary winding L1 of the coupling transformer; the second pole of the fifth fully-controlled device Q5 is connected to the primary winding L1 of the coupling transformer.

[0055] In addition, the connecting wire between the third fully-controlled device Q3 and the sixth fully-controlled device Q6 is connected to the connecting wire between the positive electrode of the second capacitor C2 and the negative electrode of the first diode D2; the connecting wire between the fourth fully-controlled device Q4 and the fifth fully-controlled device Q5 is connected to the negative electrode of the first capacitor C1, the positive electrode of the first diode D1, and the positive electrode of the second diode D2.

[0056] Example 2

[0057] Reference Figure 2 to Figure 13 , which is the second embodiment of the present invention, and is based on the previous embodiment. This embodiment provides a control method for a bidirectional DC fault interrupter, the method comprising:

[0058] S1: Determine whether a fault occurs in the main circuit unit 100.

[0059] Specifically, the fault of the main circuit unit 100 includes a forward short circuit fault and a reverse short circuit fault.

[0060] When there is no short circuit fault, the bidirectional DC fault interrupter is in standby mode. Figure 2 As shown, the first switch S1 in the main circuit unit 100 is closed to carry the load current. The conduction path only includes the first switch S1, the inductor L3, the current transformer interface MPO and the secondary winding L2 of the coupling transformer, does not include any power type devices, and has very low conduction loss.

[0061] S2: If a fault occurs, the voltage injection unit 200 is started to inject a reverse voltage into the main circuit unit 100 and the voltage in the main circuit unit 100 is reduced to zero.

[0062] When a forward short circuit fault occurs:

[0063] Due to the low inertia factor of the DC system, the current in the main circuit unit 100 rises rapidly. When the current transformer detects that the current in the main circuit unit 100 reaches the positive action threshold of the bidirectional DC fault interrupter, the voltage injection unit 200 can start working and apply a conduction signal to the first fully controlled device Q1, the second fully controlled device Q2, the third fully controlled device Q3 and the fifth fully controlled device Q5, then the first capacitor C1 and the second capacitor C2 are discharged in series and through the action of the primary winding L1 of the coupling transformer, a reverse voltage with an amplitude higher than the bus voltage is injected into the main circuit unit 100, so that the fault current in the main circuit unit 100 is rapidly reduced until it is zero, as shown in FIG. Figure 3 shown.

[0064] When a reverse short circuit fault occurs:

[0065] Due to the low inertia factor of the DC system, the current in the main circuit unit 100 rises rapidly. When the current transformer detects that the current in the main circuit unit 100 reaches the reverse action threshold of the bidirectional DC fault interrupter, the voltage injection unit 200 starts to work and applies a conduction signal to the first fully controlled device Q1, the second fully controlled device Q2, the fourth fully controlled device Q4 and the sixth fully controlled device Q6, then the first capacitor C1 and the second capacitor C2 are discharged in series and through the action of the primary winding L1 of the coupling transformer, a reverse voltage with an amplitude higher than the bus voltage is injected into the main circuit unit 100, so that the fault current in the main circuit unit 100 is rapidly reduced until it is zero, as shown in FIG. Figure 4 shown.

[0066] S3: The voltage injection unit 200 is regulated to inject a reverse voltage with an amplitude lower than the fault voltage into the main loop unit 100 so that the fault voltage rises.

[0067] When a forward short circuit fault occurs:

[0068] When the current transformer detects that the current in the main circuit unit 100 drops to zero, the voltage injection unit 200 immediately works in the multi-mode voltage injection stage, applies a shutdown signal to the first fully-controlled device Q1, and applies a conduction signal to the second fully-controlled device Q2, the third fully-controlled device Q3 and the fifth fully-controlled device Q5. Then, the second capacitor C2 discharges alone and injects a reverse voltage with an amplitude lower than the bus voltage into the main circuit unit 100 through the action of the coupling transformer (the primary winding L1 of the coupling transformer and the secondary winding L2 of the coupling transformer), so that the fault current in the main circuit unit 100 begins to rise, as shown in FIG. Figure 5 shown.

[0069] When a reverse short circuit fault occurs:

[0070] When the current transformer detects that the current in the main circuit unit 100 drops to zero, the voltage injection unit 200 immediately works in the multi-mode voltage injection stage, applies a shutdown signal to the first fully-controlled device Q1, and applies a conduction signal to the second fully-controlled device Q2, the fourth fully-controlled device Q4 and the sixth fully-controlled device Q6. Then, the second capacitor C2 discharges alone and injects a reverse voltage with an amplitude lower than the bus voltage into the main circuit unit 100 through the action of the coupling transformer (the primary winding L1 of the coupling transformer and the secondary winding L2 of the coupling transformer), so that the fault current in the main circuit unit 100 begins to rise, as shown in FIG. Figure 6 shown.

[0071] S4: The voltage injection unit 200 is regulated to modulate the fault current into a ripple current.

[0072] When a forward short circuit fault occurs:

[0073] When the current transformer detects that the current in the main circuit unit 100 rises back to the preset ripple current peak value, the first fully controlled device Q1, the second fully controlled device Q2, the third fully controlled device Q3 and the fifth fully controlled device Q5 are immediately applied with a conduction signal, the first capacitor C1 and the second capacitor C2 are discharged in series, and the current in the main circuit unit 100 begins to decrease again. Repeating steps S3 and S4 can modulate the fault current into a low-frequency ripple current.

[0074] When a reverse short circuit fault occurs:

[0075] When the current transformer detects that the current in the main circuit unit 100 rises back to the preset ripple current peak value, the first fully controlled device Q1, the second fully controlled device Q2, the fourth fully controlled device Q4 and the sixth fully controlled device Q6 are immediately applied with a conduction signal, the first capacitor C1 and the second capacitor C2 are discharged in series, and the current in the main circuit unit 100 begins to decrease again. Repeating steps S3 and S4 can modulate the fault current into a low-frequency ripple current.

[0076] S5: arc-free isolation of the main circuit unit 100 is completed.

[0077] Specifically, the modulated ripple current stage provides a longer action time window for the first switch S1 in the main circuit unit 100. The first switch S1 in the main circuit unit 100 starts to disconnect during the time period when the voltage injection unit 200 injects a higher voltage, which can create zero current and low voltage breaking conditions for the mechanical switch, thereby achieving arc-free isolation of the fault.

[0078] S6: recovering energy from the voltage injection unit 200.

[0079] Forward fault:

[0080] After the short-circuit fault is isolated without arcing, the first fully-controlled device Q1, the second fully-controlled device Q2, the third fully-controlled device Q3 and the fifth fully-controlled device Q5 are all applied with a turn-off signal, and the second switch S2 is applied with a turn-on signal, so that the energy stored in the primary winding L1 of the transformer is recovered to charge the second capacitor C2, as shown in FIG. Figure 7 shown.

[0081] When the second capacitor C2 is charged to its preset voltage, a turn-off signal is applied to the second switch S2, and the remaining energy stored in the primary winding L1 of the transformer continues to charge the first capacitor C1 until the energy is completely dissipated. Figure 8 Shown

[0082] Reverse fault:

[0083] After the short-circuit fault is isolated without arcing, the first fully-controlled device Q1, the second fully-controlled device Q2, the fourth fully-controlled device Q4 and the sixth fully-controlled device Q6 are all applied with a turn-off signal, and the second switch S2 is applied with a turn-on signal, so that the energy stored in the primary winding L1 of the transformer is recovered to charge the second capacitor C2, as shown in FIG. Fig. 9 shown.

[0084] When the second capacitor C2 is charged to its preset voltage, a turn-off signal is applied to the second switch S2, and the remaining energy stored in the primary winding L1 of the transformer continues to charge the first capacitor C1 until the energy is completely dissipated. Fig.10 shown.

[0085] It should be noted that when the current transformer detects a forward short-circuit fault and the voltage injection unit 200 starts working, the second fully-controlled device Q2, the third fully-controlled device Q3 and the fifth fully-controlled device Q5 are always in the on state until the short-circuit fault is isolated without arcing and then converted to the off state; the first fully-controlled device Q1 is the only high-frequency operating device, which is turned on when a high-amplitude reverse voltage is injected and turned off when a low-amplitude reverse voltage is injected.

[0086] When the energy of the primary winding L1 of the coupling transformer is recovered and stored, the flow loop passes through the body diodes of the third fully-controlled device Q3 and the fifth fully-controlled device Q5, and no signal is applied to conduct.

[0087] Correspondingly, when the current transformer detects a reverse short circuit fault and the voltage injection unit 200 starts working, the second fully-controlled device Q2, the fourth fully-controlled device Q4 and the sixth fully-controlled device Q6 are always in the on state until the short circuit fault is isolated without arcing and then converted to off state.

[0088] When the energy of the primary winding L1 of the coupling transformer is recovered and stored, the flow loop passes through the body diodes of the fourth fully-controlled device Q4 and the sixth fully-controlled device Q6, and no signal is applied to conduct.

[0089] Reference Fig.11 , which is the key waveform diagram when isolating the forward fault in the present invention. 0 Before the moment, the bidirectional DC fault interrupter works in the standby state;

[0090] In t 0 At this moment, a forward short-circuit fault occurs in the DC system, and the fault current rises rapidly;

[0091] In t 1 At the moment, the current transformer detects that the inductance in the main circuit unit 100 reaches the action threshold current of the bidirectional DC fault interrupter, and the voltage injection unit 200 is immediately turned on and works in the fault current suppression mode, so that the fault current is rapidly reduced. 2At this moment, the fault current drops to zero;

[0092] Then the voltage injection unit 200 starts to work in the multi-mode voltage injection stage, and the fault current can be modulated into t by alternately injecting a reverse voltage with an amplitude higher or lower than the DC bus into the main circuit unit 100. 2 ~t 3 The low-amplitude high-frequency ripple current shown in the window;

[0093] The first switch S1 in the main circuit unit 100 is disconnected when the voltage injection unit 200 works in the arc suppression mode, so that arc-free isolation of the DC fault can be completed under the conditions of zero current and low voltage;

[0094] In t 4 At time t, the second switch S2 is turned on to start recovering the energy stored in the primary winding L1 of the coupling transformer to charge the second capacitor C2. 5 At that moment, the second energy storage capacitor is charged to a preset value, and then the second switch S2 is closed, and the residual energy starts to charge the first capacitor C1 until the energy stored in the winding is completely dissipated.

[0095] Reference Fig.12 , is the key waveform diagram for isolating reverse faults in the present invention. 0 Before the moment, the bidirectional DC fault interrupter works in the standby state;

[0096] In t 0 At this moment, a reverse short-circuit fault occurs in the DC system, and the fault current drops rapidly;

[0097] In t 1 At the moment, the current transformer detects that the inductance in the main circuit unit 100 reaches the action threshold current of the bidirectional DC fault interrupter, and the voltage injection unit 200 is immediately turned on and works in the fault current suppression mode, causing the fault current to rise rapidly. 2 At this moment, the fault current rises to zero;

[0098] Then the voltage injection unit 200 starts to work in the multi-mode voltage injection stage, and the fault current can be modulated into t by alternately injecting a reverse voltage with an amplitude higher or lower than the DC bus into the main circuit unit 100. 2 ~t 3 The low-amplitude high-frequency ripple current shown in the window;

[0099] The first switch S1 in the main circuit unit 100 is disconnected when the voltage injection unit 00 works in the arc suppression mode, so that arc-free isolation of the DC fault can be completed under the conditions of zero current and low voltage;

[0100] In t 4At time t, the second switch S2 is turned on to start recovering the energy stored in the primary winding L1 of the coupling transformer to charge the second capacitor C2. 5 At that moment, the second energy storage capacitor is charged to a preset value, and then the second switch S2 is closed, and the residual energy starts to charge the first capacitor C1 until the energy stored in the winding is completely dissipated.

[0101] in addition, Fig.13 The present invention is a flow chart of a control method of a bidirectional DC fault interrupter.

[0102] In summary, the beneficial effects of the present invention are:

[0103] 1. The present invention uses two capacitors to discharge in series and injects high voltage into the main circuit unit 100 through the action of a coupling transformer. The series structure can reduce the capacity of the capacitor and reduce the voltage stress of the device.

[0104] 2. The voltage injection unit 200 included in the present invention can operate in the fault current rapid suppression stage, the multi-modal voltage injection stage and the arc suppression stage, can suppress the fault current to zero extremely quickly, can modulate the fault current into a low-amplitude and high-frequency ripple current, and can provide a zero-current and low-voltage action time window for the ultra-fast mechanical switch, thereby realizing arc-free interruption of DC faults.

[0105] 3. The full-bridge commutation structure included in the present invention can realize the injection of forward voltage and can also realize the injection of reverse voltage, so the present invention has the breaking capability of forward short-circuit fault and reverse short-circuit fault.

[0106] 4. The present invention can recycle the energy stored in the inductor winding of the transformer, can charge the energy storage capacitor, and can quickly dissipate the energy stored in the winding.

[0107] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. A bidirectional DC fault interrupter, characterized in that: include, A main circuit unit (100) comprises a first switch (S1), an inductor (L3), a current transformer interface (MPO) and a secondary winding (L2) of a coupling transformer which are sequentially connected in series; A voltage injection unit (200) comprising a power module (201), a current conversion module (202) and a secondary winding (L1) of a coupling transformer connected in sequence; The power module (201) comprises a first capacitor (C1) and a second capacitor (C2) connected in series, and is used for outputting voltage; the current conversion module (202) is capable of changing the direction of current flowing through the primary winding (L1) of the coupling transformer; the primary winding (L1) of the coupling transformer cooperates with the secondary winding (L2) of the coupling transformer to form a coupling transformer.

2. The bidirectional DC fault interrupter device according to claim 1, characterized in that: The power module (201) further comprises a first fully-controlled device (Q1) and a second fully-controlled device (Q2), and the two are connected in series between the first capacitor (C1) and the second capacitor (C2).

3. The bidirectional DC fault interrupter device according to claim 2, characterized in that: The power module (201) further comprises a first diode (D1) and a second diode (D2); the cathode of the first diode (D1) is connected to the anode of the second capacitor (C2), and the anode is connected to the cathode of the first capacitor (C1); the cathode of the second diode (D2) is connected to a wire between the first fully-controlled device (Q1) and the second fully-controlled device (Q2), and the anode is connected to the cathode of the first capacitor (C1) and the anode of the first diode (D1), respectively.

4. The bidirectional DC fault interrupter device according to claim 3, characterized in that: The power module (201) further comprises a second switch (S2), wherein the second switch (S2) short-circuits the second fully-controlled device (Q2).

5. The bidirectional DC fault interrupter device according to claim 4, characterized in that: The commutation module (202) comprises a third fully-controlled device (Q3) and a fifth fully-controlled device (Q5); the first pole of the third fully-controlled device (Q3) is connected to one end of the primary winding (L1) of the coupling transformer, and the second pole is connected to the positive pole of the second capacitor (C2); the first pole of the fifth fully-controlled device (Q5) is respectively connected to the positive pole of the first capacitor (C1), the positive pole of the first diode (D1) and the positive pole of the second diode (D2), and the second pole is connected to the other end of the primary winding (L1) of the coupling transformer.

6. The bidirectional DC fault interrupter device according to claim 5, characterized in that: The commutation module (202) further comprises a fourth fully-controlled device (Q4) and a sixth fully-controlled device (Q6); the first electrode of the fourth fully-controlled device (Q4) is respectively connected to the positive electrode of the first capacitor (C1), the positive electrode of the first diode (D1) and the positive electrode of the second diode (D2), and the second electrode is connected to one end of the primary winding (L1) of the coupling transformer; the first electrode of the sixth fully-controlled device (Q6) is connected to the other end of the primary winding (L1) of the coupling transformer, and the second electrode is connected to the positive electrode of the second capacitor (C2).

7. A control method for a bidirectional DC fault interrupter, characterized in that: Applicable to the bidirectional DC fault interrupting device as claimed in any one of claims 1 to 6, the method comprises: Determining whether a fault occurs in the main circuit unit (100); If a fault occurs, the starting voltage injection unit (200) injects a reverse voltage into the main circuit unit (100) and reduces the voltage in the main circuit unit (100) to zero; The regulating voltage injection unit (200) injects a reverse voltage with an amplitude lower than the fault voltage into the main loop unit (100) so that the fault voltage rises; A regulating voltage injection unit (200) modulates the fault current into a ripple current; Completing arc-free isolation of the main circuit unit (100); Energy recovery is performed on the voltage injection unit (200).

8. The control method of the bidirectional DC fault interrupter according to claim 7, characterized in that: The faults include a forward short circuit fault and a reverse short circuit fault.

9. The control method of the bidirectional DC fault interrupter according to claim 8, characterized in that: The voltage injection unit (200) comprises a first capacitor (C1) and a second capacitor (C2), wherein the first capacitor (C1) and the second capacitor (C2) are connected in series and discharged to inject a reverse voltage into the main loop unit (100) so that the voltage in the main loop unit (100) drops to zero.

10. The control method of the bidirectional DC fault interrupter according to claim 9, characterized in that: The method for recovering the fault voltage includes isolating the first capacitor (C1) and the second capacitor (C2) so that the second capacitor (C2) is discharged alone.

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