Hybrid dc circuit breaker

Abstract

The application provides a hybrid DC circuit breaker, comprising: a mechanical switch connected to a first current branch; and a semiconductor switch and a forced resonance injection circuit connected to a second current branch, the forced resonance injection circuit comprising first and second terminals, the first terminal of the forced resonance injection circuit being connected to one end of the semiconductor switch, and the second terminal being connected to the other end of the semiconductor switch and both ends of the mechanical switch; wherein when the mechanical switch is in the process of being turned off, the semiconductor switch is controlled to be turned on, and at the same time the forced resonance injection circuit is controlled to inject an injection current opposite to the current direction in the mechanical switch and gradually increasing to the mechanical switch, so that the current in the mechanical switch gradually decreases to zero within a predetermined commutation time and the current is commutated from the first current branch to the second current branch. The hybrid DC circuit breaker of the application can safely and reliably turn off fault and load currents in any direction.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of circuit breakers, in particular to a hybrid DC circuit breaker. BACKGROUND

[0002] Since the DC power supply system lacks voltage zero-crossing point, the DC power supply system has the problem that the fault current is difficult to cut off. In order to quickly cut off the fault current and make the mechanical switch have no arc breaking, the current hybrid DC circuit breaker is proposed, which includes a mechanical switch, a semiconductor switch connected in parallel with the mechanical switch, and a surge arrester (or lightning arrester, surge protector or surge protector).

[0003] The basic principle of the hybrid DC circuit breaker is that when a fault current (such as a short-circuit current) occurs in the DC circuit, the mechanical switch is triggered to open. In order to avoid the arc generated in the process of opening the mechanical switch as much as possible, the semiconductor switch is controlled to be turned on first, so as to commutate the current to the semiconductor switch, and then the mechanical switch is opened. After the mechanical switch is opened, the semiconductor switch is then opened, thereby completing the process of quickly breaking the short-circuit current, and the surge arrester is used to absorb the residual electrical energy in the DC power supply system.

[0004] However, the existing hybrid DC circuit breaker cannot ensure that the mechanical switch is completely arc-free breaking, and cannot determine when to turn on the semiconductor switch to make the mechanical switch safely and reliably cut off the fault current. SUMMARY

[0005] In view of the above technical problems existing in the prior art, the present application provides a hybrid DC circuit breaker, comprising:

[0006] a mechanical switch connected to the first current branch; and

[0007] a semiconductor switch and a forced resonance injection circuit connected to the second current branch, the forced resonance injection circuit comprising a first terminal and a second terminal, the first terminal of the forced resonance injection circuit being connected to one end of the semiconductor switch, and the second terminal of the forced resonance injection circuit and the other end of the semiconductor switch being connected to both ends of the mechanical switch;

[0008] wherein, when the mechanical switch is in the process of opening, the semiconductor switch is controlled to be turned on, and at the same time the forced resonance injection circuit is controlled to inject an injection current opposite to the current direction in the mechanical switch and gradually increasing to the mechanical switch, so that the current in the mechanical switch gradually decreases to zero within a predetermined commutation time and the current is commutated from the first current branch to the second current branch.

[0009] Preferably, the forced resonant injection circuit is controlled to stop outputting the injection current when the current in the mechanical switch falls to zero within a predetermined commutation time.

[0010] Preferably, the semiconductor switch is controlled to be turned off when the contact spacing of the mechanical switch reaches a predetermined threshold.

[0011] Preferably, the forced resonant injection circuit comprises: a DC power supply, which is powered by a DC voltage on the first current branch or an external power supply, to charge a DC bus capacitor; a DC bus connected to the DC bus capacitor and used to provide current to the forced resonant injection circuit; an inverter provided with switching pulses during current injection to generate square wave periodic voltage pulses with alternating polarity; a resonant circuit comprising an inductor and a capacitor connected in series, one end of which is connected to the output of the inverter, and the other end of which is used to output alternating current with gradually increasing amplitude; a rectifier circuit, the input of which is connected to the other end of the resonant circuit, and the output of which is used to output pulsating DC with gradually increasing amplitude; and an output module, the input of which is electrically connected to the output of the rectifier circuit, and the output of which serves as the first terminal and the second terminal of the forced resonant injection circuit, the output module being used to filter and amplify the pulsating DC and output the injection current; wherein the inverter, the resonant circuit, the equivalent resistance, the equivalent inductance and the equivalent capacitance of the circuit connected between the other end of the resonant circuit and the output of the inverter form an under-damped resonant circuit, and the frequency of the square wave periodic voltage pulses depends on the resonant frequency of the under-damped resonant circuit.

[0012] Preferably, the semiconductor switch is a bidirectional controllable semiconductor switch; the hybrid DC circuit breaker further comprises a polarity module connected between the rectifier circuit and the output module, the polarity module comprising a full-bridge circuit controlled to change the polarity of the input current and the output current of the polarity module.

[0013] Preferably, the inverter is a single-level, double-level or multi-level full-bridge inverter or a half-bridge inverter.

[0014] Preferably, the output module is configured to generate a current break between its input and the first current branch.

[0015] Preferably, the output module is a autotransformer comprising a first winding and a second winding, a first terminal of the first winding being electrically connected to a first output terminal of the rectifier circuit, a second terminal of the first winding being electrically connected to a first terminal of the second winding and serving as a first output terminal of the forced resonant injection circuit, a second terminal of the second winding being electrically connected to a second output terminal of the rectifier circuit and serving as a second output terminal of the forced resonant injection circuit.

[0016] Preferably, the transformer or the autotransformer is coreless.

[0017] Preferably, the polarity module comprises: a first and a second switching transistor connected to form a first bridge arm, a first node formed by the first and the second switching transistor being connected as the first polarity terminal; a third and a fourth switching transistor connected to form a second bridge arm, a second node formed by the third and the fourth switching transistor being connected as the second polarity terminal; wherein a first electrode of the first switching transistor and a first electrode of the third switching transistor are connected to a positive output terminal of the rectifier circuit, and a second electrode of the second switching transistor and a second electrode of the fourth switching transistor are connected to a negative output terminal of the rectifier circuit.

[0018] Preferably, the hybrid DC circuit breaker further comprises a surge arrester connected in parallel with the semiconductor switch.

[0019] In the normal power supply process of the DC power supply system, the forced resonance injection circuit has zero power consumption. When a fault current occurs in the DC power supply system, the forced resonance injection circuit controllably injects an injection current in the opposite direction and gradually increases the injection current to the mechanical switch, controls the time of current commutation, and makes the mechanical switch have a small recovery voltage, so that the mechanical switch can safely and reliably break the fault current. BRIEF DESCRIPTION OF DRAWINGS

[0020] The embodiments of the present application will be further described below with reference to the accompanying drawings, in which:

[0021] Figure 1 is a block diagram of a hybrid DC circuit breaker according to a preferred embodiment of the present application.

[0022] Figure 2 is Figure 1 is a current waveform diagram in the hybrid DC circuit breaker shown in

[0023] Figure 3 shows Figure 1 is a specific block diagram of a forced resonance injection circuit in the hybrid DC circuit breaker shown in

[0024] Figure 4 is Figure 3 is a waveform diagram of a resonance current output by a resonance circuit in the forced resonance injection circuit shown in

[0025] Figure 5 is Figure 3 is a waveform diagram of a rectification current output by a rectifier circuit in the forced resonance injection circuit shown in

[0026] Figure 6 is Figure 3Waveform diagram of the injection current outputted by the output module in the forced resonant injection circuit.

[0027] Figure 7 is a specific circuit diagram of the hybrid DC circuit breaker according to the first embodiment of the present application.

[0028] Figure 8 is a specific circuit diagram of the polarity module in the hybrid DC circuit breaker according to the second embodiment of the present application.

[0029] Figure 9 is a specific circuit diagram of the output module in the hybrid DC circuit breaker according to the third embodiment of the present application.

[0030] Figure 10 is a specific circuit diagram of the semiconductor switch in the hybrid DC circuit breaker according to the fourth embodiment of the present application.

[0031] Figure 11 is a specific circuit diagram of the inverter in the hybrid DC circuit breaker according to the fifth embodiment of the present application. DETAILED DESCRIPTION

[0032] In order to make the objects, technical solutions and advantages of the present application clearer, the present application will be further described in detail below with reference to the accompanying drawings.

[0033] Figure 1 is a block diagram of the hybrid DC circuit breaker according to the preferred embodiment of the present application. As shown in Figure 1 , the hybrid DC circuit breaker 1 comprises a mechanical switch 11 connected to a first current branch, and a semiconductor switch 13 and a forced resonant injection circuit 14 connected to a second current branch. The forced resonant injection circuit 14 comprises a terminal 1461 and a terminal 1462, the terminal 1461 of the forced resonant injection circuit 14 is connected to one end of the semiconductor switch 13, and the other end of the semiconductor switch 13 and the terminal 1462 of the forced resonant injection circuit 14 are connected to both ends of the mechanical switch 11. The hybrid DC circuit breaker 1 further comprises a surge arrester 12 connected in parallel with the semiconductor switch 13.

[0034] For the convenience of the following description, in Figure 1 , the directions of the current I SW in the mechanical switch 11, the current I A in the surge arrester 12, the current I B in the semiconductor switch 13, the injection current I C outputted by the forced resonant injection circuit 14, and the current I CB in the hybrid DC circuit breaker 1 are respectively indicated by arrows.

[0035] The forced resonance injection circuit 14 is controlled to output an injection current I C which gradually increases C The current I SW flows into the mechanical switch 11 in a direction opposite to the direction of the current I SW in the mechanical switch 11, and is used to gradually reduce the current I A in the mechanical switch 11 to zero within a predetermined commutation time.

[0036] Figure 2 is Figure 1 a current waveform diagram in the hybrid DC circuit breaker 1 shown in FIG. 1. As shown in FIG. 1, before time t1, the DC power supply system is in a normal power supply state, there is no fault current in the circuit, the mechanical switch 11 is in a conducting state, and the semiconductor switch 13 is in a non-conducting state, the DC power supply system normally supplies power to the load (not shown) through the conducting mechanical switch 11, at this time, the current I B in the surge arrester 12, the current I C in the semiconductor switch 13, and the injection current I SW output by the forced resonance injection circuit 14 are all zero, and the current I CB in the mechanical switch 11 is equal to the current I SW in the hybrid DC circuit breaker 1. Since the current in the forced resonance injection circuit 14 is zero, the power loss of the forced resonance injection circuit 14 is zero in the normal power supply process.

[0037] At time t1, when the load is short-circuited, the current I CB in the mechanical switch 11 sharply rises, and the current I SW in the hybrid DC circuit breaker 1 sharply rises.

[0038] At time t2, when the current I SW in the mechanical switch 11 rises to the tripping current, the control device or the tripping circuit (not shown) starts to control the mechanical switch 11 to open. Figure 1

[0039] At time t2 to time t3, the contacts of the mechanical switch 11 are in a separation process, the current I CB in the mechanical switch 11 gradually increases, and the current I C in the hybrid DC circuit breaker 1 gradually increases.

[0040] At time t3, the semiconductor switch 13 is controlled to be conducting, and at the same time, the forced resonance injection circuit 14 is controlled to output the injection current I C from time t3, the direction of the injection current I SW is from the terminal 1461 to the terminal 1462, and along the direction opposite to the direction of the current I C in the mechanical switch 11.​SW The direction opposite to that of the mechanical switch 11 is injected.

[0041] Between time t3 and time t4, the injection current I output by the forced resonant injection circuit 14 is... C The current I in semiconductor switch 13 gradually increases. B Gradually increase, due to the injected current I C The direction of the current I in mechanical switch 11 SW The directions are opposite, causing the current I in mechanical switch 11 to flow in the opposite directions. SW The current gradually decreases. During this process, the current I in mechanical switch 11... SW The current gradually switches to semiconductor switch 13, and the current I in semiconductor switch 13... B and the current I in the hybrid DC circuit breaker 1 CB It continues to rise.

[0042] At time t4, the current I in mechanical switch 11 is... SW The value is zero, at which point the current commutation process is completed, controlling the injection current I output by the forced resonant injection circuit 14. C The current is zero, so the injection of current into mechanical switch 11 stops.

[0043] Between time t4 and time t5, the short-circuit current flows only through the semiconductor switch 13, which is in the on state. At this time, the current I in the semiconductor switch 13 is... B The current I in the hybrid DC circuit breaker 1 continues to increase. CB The distance gradually increases. During this process, the moving contact of the mechanical switch 11 continues to open at a speed of several meters per second, and the distance between the moving and stationary contacts reaches the predetermined contact distance at time t5. This is due to the injection current I output by the forced resonant injection circuit 14. C This causes the current I in mechanical switch 11 to SW The circuit has been switched to semiconductor switch 13, and mechanical switch 11 will not be subjected to a large current interruption during this process, meaning it does not need to be disconnected under a large current. Specifically, mechanical switch 11 will achieve zero-current turn-off and arc-free turn-off.

[0044] At time t5, the control device ( Figure 1 (Not shown) Controls the semiconductor switch 13 to be in the off or open state, and the current I in the semiconductor switch 13 is... B The current I in the hybrid DC circuit breaker 1 drops to zero. CB It has reached its maximum value.

[0045] At time t5~time t6, since there is no potential zero crossing point in the DC power supply system, the residual energy in the DC power supply system will be discharged through the surge arrester 12 and the terminals 1461, 1462 of the forced resonant injection circuit 14, and the surge arrester 12 will start to consume the energy in the DC power supply system, so that the current I A gradually decreases to zero, and the current I CB gradually decreases to zero. Finally, at time t6, the fault is cleared.

[0046] The two terminals 1461, 1462 of the forced resonant injection circuit 14 in the hybrid DC circuit breaker 1 are connected in series with the semiconductor switch 13 on the second current branch, and are not connected on the first current branch where the mechanical switch 11 is located, so that during normal power supply or transmission of DC power, the DC power supply system only supplies power to the load through the mechanical switch 11, and the power consumption of the forced resonant injection circuit 14 is zero.

[0047] In addition, during the opening process of the mechanical switch 11, the forced resonant injection circuit 14 of the present application can controllably inject an injection current I SW which is opposite in direction to the current I C and gradually increases, to control the current I SW in the mechanical switch 11.

[0048] The forced resonant injection circuit 14 can control the current change rate of the current I B in the semiconductor switch 13 at the end of current commutation time t4, and a smaller current change rate makes the mechanical switch 11 have a larger fast opening capability and a smaller opening loss. At the end of current commutation (i.e. time t4), the recovery voltage across the mechanical switch 11 depends on the resistance of the semiconductor switch 13 and the current I B in the semiconductor switch 13, which can make the recovery voltage across the mechanical switch 11 smaller, for example, a few volts to a few tens of volts. At the end of current commutation, the mechanical switch 11 has a smaller current change rate, and the mechanical switch 11 has a smaller recovery voltage across it, so that the mechanical switch 11 can be safely and reliably opened.

[0049] The time period from time t4 to time t5 is the off delay time of the hybrid DC circuit breaker 1, which is used to make the distance between the moving and stationary contacts of the mechanical switch 11 reach a predetermined contact distance within the off delay time, wherein the predetermined contact distance and the off delay time depend on the recovery voltage of the mechanical switch 11 and the opening speed of the moving contact.

[0050] When the hybrid DC circuit breaker 1 is used in a bidirectional DC power supply system, for example when the current direction in the hybrid DC circuit breaker 1 is different from the aforementioned current I... CB When the directions are opposite, the forced resonant injection circuit 14 is controlled to output a gradually increasing injection current at its terminal 1461.

[0051] Figure 3 It shows Figure 1 The diagram shows a specific block diagram of the forced resonant injection circuit in the hybrid DC circuit breaker. (See diagram for example.) Figure 3 As shown, the forced resonant injection circuit 24 includes a DC power supply 241, a DC bus capacitor C1 connected between DC buses, an inverter 242, a resonant circuit 243, a rectifier circuit 244, a polarity module 245, and an output module 246. The input terminal of the inverter 242 is connected to the DC power supply 241, and its output terminal is connected to the input terminal of the rectifier circuit 244 through the resonant circuit 243. The output terminal of the rectifier circuit 244 is connected to the input terminal of the polarity module 245, and the output terminal of the polarity module 245 is connected to the input terminal of the output module 246. One terminal 2461 of the output module 246 is connected to one end of the semiconductor switch 23, and the other terminal 2462 is connected to one end of the mechanical switch 21.

[0052] The DC power supply 241 is powered by the DC voltage on the first current branch or by an external power source to charge the DC bus capacitor C1; the DC bus capacitor C1 provides current to the forced resonant injection circuit through the DC bus.

[0053] The equivalent resistance, equivalent capacitance, and equivalent inductance of the inverter 242, resonant circuit 243, rectifier circuit 244, polarity module 245, and output module 246 form an underdamped resonant circuit.

[0054] Control device ( Figure 3 (Not shown) A high-frequency (e.g., 10–100 kHz) pulse-width modulation signal, i.e., a switching pulse, is provided to inverter 242, causing inverter 242 to convert the DC current on DC bus capacitor C1 into AC current, i.e., alternating polarity square wave periodic voltage pulses. The frequency of the square wave periodic voltage pulses depends on the resonant frequency of the underdamped resonant circuit, causing resonant circuit 243 to output a resonant current I. RES .

[0055] The output module 246 is also configured to generate a current disconnect between its input and the first current branch.

[0056] Figure 4 yes Figure 3 The waveform of the resonant current output by the resonant circuit in the forced resonant injection circuit is shown. Figure 4 As shown, the resonant current I RESFor the AC voltage with gradually increasing amplitude, the resonant frequency is determined by the inherent frequency of the inductance, capacitance and equivalent resistance (such as the bulk resistance of the inductance and the capacitance) of the equivalent load circuit. At the beginning of oscillation, the inverter 242 outputs the voltage to the resonant circuit 243, whereby the resonant circuit 243 begins to generate the oscillation current. When the resonant current I RES At each zero-crossing point, the inverter 242 is controlled to switch the output voltage polarity, and the electric energy on the DC bus capacitor C1 is output to the resonant circuit 243 through the inverter 242, thereby providing the electric energy in each switching cycle, so that the resonant current I RES with gradually increasing amplitude is output by the resonant circuit 243.

[0057] The rectifier circuit 244 is used to rectify the resonant current I RES output by the resonant circuit 243 into pulsed DC.

[0058] Figure 5 is Figure 3 the waveform diagram of the rectified current output by the rectifier circuit in the forced resonant injection circuit shown in Figure 5 As shown in , the rectified current I R is the pulsed DC with unchanging current direction and periodically increasing amplitude.

[0059] The polarity module 245 includes a positive input terminal, a negative input terminal, a polarity terminal 2451 and a polarity terminal 2452, and the positive and negative input terminals of the polarity module 245 are connected to the positive and negative output terminals of the rectifier circuit 244, respectively. The polarity module 245 can controllably make its polarity terminals 2451, 2452 be the positive and negative output terminals, or make its polarity terminals 2451, 2452 be the negative and positive output terminals. Thus, the polarity module 245 outputs the pulsed DC with the same phase or opposite phase as the pulsed DC output by the rectifier circuit 244.

[0060] The output module 246 is used to filter or reduce the AC component in the pulsed DC output by the polarity module 245, thereby outputting the DC with gradually increasing amplitude and smoothness.

[0061] Figure 6 is Figure 3 the waveform diagram of the injection current output by the output module in the forced resonant injection circuit shown in Figure 6 As shown in , the injection current I C output by the output module 246 is the smooth DC with gradually increasing amplitude. The injection current I C is output from the terminal 2462 of the output module 246 and flows into the mechanical switch 21, thereby making the current in the mechanical switch 21 gradually decrease to zero within the current commutation time.

[0062] By providing the inverter 242 with a high frequency (e.g. 10-100 KHz) pulse width modulated signal, the output module 246 is able to output a gradually increasing and smooth DC current within a few cycles of the switching frequency (e.g. tens to hundreds of microseconds) to enable the fault current in the mechanical switch 21 to be rapidly commutated into the semiconductor switch 23.

[0063] In other embodiments of the application, when the hybrid DC circuit breaker 2 is used in a unidirectional DC power supply system, the hybrid DC circuit breaker 2 can not have the polarity module 245, and the semiconductor switch 23 can be a unidirectional controllable semiconductor switch.

[0064] Figure 7 is a specific circuit diagram of the hybrid DC circuit breaker according to the first embodiment of the application. As shown in Figure 7 , the semiconductor switch 33 is a bidirectional controllable switch, comprising an insulated gate bipolar transistor T31 with a reverse parallel diode and an insulated gate bipolar transistor T32 with a reverse parallel diode, wherein the emitter of the insulated gate bipolar transistor T31 is connected to the emitter of the insulated gate bipolar transistor T32. By controlling the conduction of the insulated gate bipolar transistor T31 or T32, the unidirectional conduction of the DC current is achieved.

[0065] The inverter 342 is a full-bridge inverter composed of four field effect transistors.

[0066] The resonant circuit 343 comprises an inductor L3 and a capacitor C3 in series. By selecting the inductor L3 and the capacitor C3 with appropriate parameters, an under-damped resonant circuit is formed when , where R', L' and C' are the equivalent resistance value, the equivalent inductance value and the equivalent capacitance value of the inverter 342, the resonant circuit 343, the rectifier circuit 344, the polarity module 345 and the output module 346 respectively. For example, when the equivalent resistance value, the equivalent inductance value and the equivalent capacitance value are 3.5 ohms, 150 μH and 82 nF respectively, an under-damped resonant circuit is formed.

[0067] The switching frequency of the inverter 342 depends on the resonant frequency of the under-damped resonant circuit. For example, by selecting the inductor L3 of 150 μH and the capacitor C3 of 82 nF, the switching frequency of the inverter 342 is , i.e. about 45 KHz.

[0068] When two of the diagonally opposite IGBTs in the control inverter 342 are turned on, the DC power supply 341 outputs electric energy through the two turned-on IGBTs, and thus the resonant circuit 343 outputs a current of a first polarity. When the other two of the diagonally opposite IGBTs in the control inverter 342 are turned on, the DC power supply 341 outputs electric energy through the two turned-on IGBTs, and thus the resonant circuit 343 outputs a current of a second polarity with an increased amplitude. The IGBTs in the control inverter 342 are turned on in the above two manners alternately, so that the resonant circuit 343 outputs alternating current with gradually increased amplitudes in a plurality of switching periods of the pulse width modulation signal.

[0069] The rectifier circuit 344 is a full-wave rectifier circuit including four diodes.

[0070] The polarity module 345 includes a full-bridge circuit controlled to change the polarity of the input current and the output current of the polarity module. Specifically, the polarity module 345 includes four IGBTs T33, T34, T35 and T36 with reverse-parallel diodes, and diodes D33, D34, D35 and D36 connected in series with the IGBTs T33, T34, T35 and T36 respectively. The node N1 formed by connecting the IGBT T33 and the diode D33 in series and the IGBT T34 and the diode D34 in series is the polarity terminal 3451 of the polarity module 345, and the node N2 formed by connecting the IGBT T35 and the diode D35 in series and the IGBT T36 and the diode D36 in series is the polarity terminal 3452 of the polarity module 345. When the diagonally opposite IGBTs T33 and T36 are controlled to be turned on, the polarity terminals 3451 and 3452 are the positive output terminal and the negative output terminal of the polarity module 345 respectively. When the diagonally opposite IGBTs T34 and T35 are controlled to be turned on, the polarity terminals 3451 and 3452 are the negative output terminal and the positive output terminal of the polarity module 345 respectively.

[0071] The output module 346 is a self-coupled transformer, which is coreless to prevent magnetic saturation. The self-coupled transformer includes a winding L31 and a winding L32, the same-named end of the winding L31 is connected to the node N1, the same-named end of the winding L32 is connected to the non-same-named end of the winding L31 and is the terminal 3461 of the output module 346, and the non-same-named end of the winding L32 is connected to the node N2 and is the terminal 3462 of the output module 346.

[0072] When the polarity terminal 3452 of the polarity module 345 outputs a current I31 and flows into the non-same name end of the winding L32, the current I31 flows from the non-same name end of the winding L31 to its same name end, and the same name end of the winding L32 to its non-same name end has a current I32, the terminal 3462 outputs an injection current I C , wherein the injection current I C is equal to the sum of the current I31 and the current I32. The injection current I C is injected into the mechanical switch 31, so that the current I SW in the mechanical switch 31 gradually decreases to zero within a predetermined current commutation time.

[0073] Figure 8 is a specific circuit diagram of a polarity module in a hybrid DC circuit breaker according to the second embodiment of the present application. As shown in Figure 8 , the polarity module 445 includes four insulated gate bipolar transistors T43, T44, T45 and T46 without reverse parallel diodes, wherein the insulated gate bipolar transistors T43 and T44 are connected to form one bridge arm, and the insulated gate bipolar transistors T45 and T46 are connected to form another bridge arm. Specifically, the collectors of the insulated gate bipolar transistors T43 and T45 are connected and used for being connected to a positive output terminal of a rectifier circuit, the emitters of the insulated gate bipolar transistors T44 and T46 are connected and used for being connected to a negative output terminal of the rectifier circuit, a node N41 formed by the connection of the emitter of the insulated gate bipolar transistor T43 and the collector of the insulated gate bipolar transistor T44 serves as one polarity terminal 4451 of the polarity module 445, and a node N42 formed by the connection of the emitter of the insulated gate bipolar transistor T45 and the collector of the insulated gate bipolar transistor T46 serves as another polarity terminal 4452 of the polarity module 445.

[0074] When the diagonally opposite insulated gate bipolar transistors T43 and T46 are controlled to be conductive and the insulated gate bipolar transistors T44 and T45 are controlled to be non-conductive, the polarity terminals 4451 and 4452 serve as the positive output terminal and the negative output terminal respectively, wherein the current flows out from the polarity terminal 4451 and flows into the polarity terminal 4452. When the other diagonally opposite insulated gate bipolar transistors T44 and T45 are controlled to be conductive and the insulated gate bipolar transistors T43 and T46 are controlled to be non-conductive, the polarity terminals 4451 and 4452 serve as the negative output terminal and the positive output terminal respectively, wherein the current flows out from the polarity terminal 4452 and flows into the polarity terminal 4451.

[0075] Figure 9 is a specific circuit diagram of an output module in a hybrid DC circuit breaker according to the third embodiment of the present application. As shown in Figure 9As shown, the output module 446 is a coreless transformer, which includes a primary winding L41 and a secondary winding L42, wherein the same and non-same terminals of the primary winding L41 are respectively connected to the positive and negative output terminals of the rectifier circuit 244, or connected to the two polarity terminals 2451, 2452 of the polarity module 245, and the same and non-same terminals of the secondary winding L42 are respectively used as the output terminals 4461, 4462 and connected to the semiconductor switch and the mechanical switch. When the current flows from the non-same terminal to the same terminal of the primary winding L41, the current in the secondary winding L42 flows from the output terminal 4461 to the output terminal 4462. The coreless transformer 446 has the current isolation function, and at the same time, can reduce the high-frequency resonance current I RES Power consumption caused in the transmission process.

[0076] Figure 10 is a specific circuit diagram of the semiconductor switch in the hybrid DC circuit breaker according to the fourth embodiment of the present application. As shown, Figure 10 The semiconductor switch 43 includes a bridge circuit formed by four diodes D41, D42, D43 and D44, and an insulated gate bipolar transistor T41, whose collector is connected to the negative poles of the diodes D41 and D43, and whose emitter is connected to the positive poles of the diodes D42 and D44. When the insulated gate bipolar transistor T41 is controlled to be conductive, one of the conductive paths is that the current flows from the terminal 431, passes through the diode D41, the conductive insulated gate bipolar transistor T41, the diode D44 to the terminal 432; and the other conductive path is that the current flows from the terminal 432, passes through the diode D43, the conductive insulated gate bipolar transistor T41, the diode D42 to the terminal 431.

[0077] Figure 11 is a specific circuit diagram of the inverter in the hybrid DC circuit breaker according to the fifth embodiment of the present application. As shown, Figure 11 The inverter 442 is a half-bridge inverter, which includes insulated gate bipolar transistors T47, T48, and capacitors C41 and C42, wherein the positive and negative input terminals of the half-bridge inverter 442 are respectively electrically connected to the positive and negative poles of the DC power supply 241, for inverting the DC power output by the DC power supply 241 into AC power. The half-bridge inverter 442 has only two switching transistors, thus can save the device cost.

[0078] In other embodiments of the present application, the inverter can also be a single-level, double-level or multi-level full-bridge (H-bridge) inverter.

[0079] In another embodiment of the present application, a switching transistor such as a metal-oxide-semiconductor field-effect transistor (MOSFET) or the like can be employed in place of the semiconductor switch 33 and / or the insulated-gate bipolar transistor in the polarity module 345 in the above-described embodiment.

[0080] In another embodiment of the present application, the hybrid DC circuit breaker can include a plurality of semiconductor switches 33 connected in series.

[0081] In another embodiment of the present application, the rectifying circuit 244 can employ a half-wave rectifying circuit or the like to rectify alternating current into pulsating direct current.

[0082] While the present application has been described with reference to the preferred embodiments thereof, it is to be understood that the application is not limited to the embodiments described above but includes various changes and modifications which can be made to the application without departing from the scope of the application.

Claims

1. A hybrid DC circuit breaker, characterized by Comprising: a mechanical switch connected in the first current branch; and a semiconductor switch and a forced resonant injection circuit connected in the second current branch, the forced resonant injection circuit comprising a first terminal and a second terminal, the first terminal of the forced resonant injection circuit being connected to one end of the semiconductor switch, and the second terminal of the forced resonant injection circuit and the other end of the semiconductor switch being connected to both ends of the mechanical switch; wherein, when the mechanical switch is in the process of being opened, the semiconductor switch is controlled to be turned on, and at the same time the forced resonant injection circuit is controlled to inject an injection current into the mechanical switch, which is opposite in direction to the current in the mechanical switch and gradually increases, so that the current in the mechanical switch gradually decreases to zero within a predetermined commutation time and the current is gradually commutated from the first current branch to the second current branch, wherein the forced resonant injection circuit comprises: a DC power supply, the power source of which is from a DC voltage on the first current branch or an external power source, to charge a DC bus capacitor; a DC bus connected to the DC bus capacitor, and used to provide current to the forced resonant injection circuit; an inverter provided with switching pulses during current injection to generate square wave periodic voltage pulses with alternating polarity; a resonant circuit comprising an inductor and a capacitor in series, one end of which is connected to the output of the inverter, and the other end of which is used to output an alternating current with gradually increasing amplitude; a rectifier circuit, the input end of which is connected to the other end of the resonant circuit, and the output end of which is used to output a pulsating DC with gradually increasing amplitude; and an output module, the input end of which is electrically connected to the output end of the rectifier circuit, and the output end of which serves as the first terminal and the second terminal of the forced resonant injection circuit, the output module being used to filter and amplify the pulsating DC and output the injection current; wherein the equivalent resistance, equivalent inductance and equivalent capacitance of the inverter, resonant circuit, rectifier circuit and output module form an underdamped resonant circuit, and the frequency of the square wave periodic voltage pulses depends on the resonant frequency of the underdamped resonant circuit.

2. The hybrid DC circuit breaker according to claim 1, characterized in that When the current in the mechanical switch decreases to zero within the predetermined commutation time, the forced resonant injection circuit is controlled to stop outputting the injection current.

3. The hybrid DC circuit breaker according to claim 2, characterized in that When the contact spacing of the mechanical switch reaches a predetermined threshold, the semiconductor switch is controlled to be turned off.

4. The hybrid DC circuit breaker according to claim 1, characterized in that: the semiconductor switch is a bidirectional controllable semiconductor switch; the hybrid DC circuit breaker further comprises a polarity module connected between the rectifier circuit and the output module, the polarity module comprising a full-bridge circuit controlled to change the polarity of the input current and the output current of the polarity module.

5. The hybrid DC circuit breaker according to claim 1, characterized in that the inverter is a single-level, double-level or multi-level full-bridge inverter or a half-bridge inverter.

6. The hybrid DC circuit breaker according to claim 1, characterized in that the output module is configured as a transformer to generate a current break between its input end and the first current branch.

7. The hybrid DC circuit breaker according to claim 1, characterized in that The output module is a autotransformer comprising a first winding and a second winding, a first terminal of the first winding is electrically connected to a first output terminal of the rectifier circuit, a second terminal of the first winding is electrically connected to a first terminal of the second winding, and the first terminal of the second winding is electrically connected to a second output terminal of the rectifier circuit, and is a first output terminal of the forced resonance injection circuit, a second terminal of the second winding is electrically connected to a second output terminal of the rectifier circuit, and is a second output terminal of the forced resonance injection circuit.

8. The hybrid DC circuit breaker according to claim 7, characterized in that The transformer or the autotransformer is coreless.

9. The hybrid DC circuit breaker according to claim 4, characterized in that The polarity module comprises: a first and a second switching transistor connected to form a first bridge arm, a first node formed by the first and the second switching transistor being a first polarity terminal; a third and a fourth switching transistor connected to form a second bridge arm, a second node formed by the third and the fourth switching transistor being a second polarity terminal; wherein a first electrode of the first switching transistor and a first electrode of the third switching transistor are connected to a positive output terminal of the rectifier circuit, and a second electrode of the second switching transistor and a second electrode of the fourth switching transistor are connected to a negative output terminal of the rectifier circuit.

10. The hybrid DC circuit breaker according to any of claims 1 to 3, characterized in that The hybrid DC circuit breaker further comprises a surge arrester connected in parallel with the semiconductor switch.

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