Hybrid DC circuit breaker

Abstract

To provide a hybrid DC circuit breaker that can cut off failure and load currents in any direction with safety and with certainty.SOLUTION: A forced resonance injection circuit includes a first terminal and a second terminal. The first terminal of the forced resonance injection circuit is connected with one end of a semiconductor switch, and the second terminal and the other end of the semiconductor switch are connected with two ends of a mechanical switch, respectively. When the mechanical switch is in a process of being switched to an off state, the semiconductor switch is controlled to be turned on, and simultaneously, the forced resonance injection circuit is controlled to inject a gradually increasing injection current to the mechanical switch in an opposite direction to a current of the mechanical switch. As a result, a current in the mechanical switch gradually decreases to zero within a predetermined bypass time, and the current is bypassed from a first current branch to a second current branch.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This invention relates to the field of circuit breakers, and more specifically, to hybrid DC circuit breakers. [Background technology]

[0002] DC power systems lack a zero-voltage crossover, making it difficult to interrupt fault currents in them. To quickly interrupt fault currents and allow mechanical switches to switch off without causing arcs, hybrid DC circuit breakers are now available. A hybrid DC circuit breaker includes a mechanical switch and a semiconductor switch, and a surge arrester (also known as a surge protector, surge protector, or surge protection device) connected in parallel to the mechanical switch.

[0003] The basic principle of a hybrid DC circuit breaker is as follows: When a fault current (such as a short-circuit current) occurs in the DC circuit, a mechanical switch is triggered to switch off. In the process of switching off the mechanical switch, the semiconductor switch is controlled to switch off first to prevent the mechanical switch from generating an arc during the switching process, and as a result, the current is diverted to the semiconductor switch. Then the mechanical switch is switched off. After the mechanical switch has been switched off, the semiconductor switch is then switched off, thereby completing the rapid interruption process of the short-circuit current. Surge arresters are used to absorb residual electrical energy in the DC power system.

[0004] However, existing hybrid DC circuit breakers cannot ensure that switching the mechanical switch off is completely arc-free, and when switching the semiconductor switch, they cannot determine when to switch the semiconductor switch on in order to safely and reliably interrupt the fault current to the mechanical switch. [Overview of the project]

[0005] Regarding the aforementioned technical problems in the prior art, the present invention provides a hybrid DC circuit breaker, comprising: a mechanical switch connected on a first current branch; a semiconductor switch and a forced resonance injection circuit connected on a second current branch, the forced resonance injection circuit having 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 two ends of the mechanical switch; when the mechanical switch is in the process of switching off, the semiconductor switch is controlled to turn on, and at the same time, the forced resonance injection circuit is controlled to inject an injection current that gradually increases in a direction opposite to the current of the mechanical switch into 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.

[0006] Preferably, when the mechanical switch current decreases to zero within a predetermined commutation time, the forced resonance injection circuit is controlled to stop the output of the injection current.

[0007] Preferably, when the contact pitch of the mechanical switch reaches a predetermined threshold, the semiconductor switch is controlled to turn off.

[0008] Preferably, the forced resonance injection circuit includes a DC power supply powered by a first current branch or the DC voltage of 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 resonance injection circuit, an inverter to generate a periodic square-wave voltage pulse having alternating polarities, the inverter being provided with a switching pulse during current injection, a resonance circuit including an inductor and a capacitor connected in series with each other, the resonance circuit having one end connected to the output end of the inverter and another end used to output an alternating current having a gradually increasing amplitude, a rectifier circuit having an input end connected to the other end of the resonance circuit and an output end used to output a pulsating direct current having a gradually increasing amplitude, and an output module having an input end electrically connected to the output end of the rectifier circuit and an output end used as the first terminal and the second terminal of the forced resonance injection circuit, the output module being used to filter and amplify the pulsating direct current and to output an injection current. The inverter, the resonance circuit, and the equivalent resistor, equivalent inductor, and equivalent capacitor of the circuit connected between the other end of the resonance circuit and the output end of the inverter form an underdamped resonance circuit, and the frequency of the periodic square-wave voltage pulse depends on the resonance frequency of the underdamped resonance circuit.

[0009] Preferably, the semiconductor switch is a bidirectionally controllable semiconductor switch, and the hybrid DC circuit breaker further includes a polarity module connected between the rectifier circuit and the output module, the polarity module including a full-bridge circuit controlled to change the polarities of the input current and the output current of the polarity module.

[0010] Preferably, the inverter is a single-level, two-level, or multi-level full-bridge inverter, or a half-bridge inverter.

[0011] Preferably, the output module is configured to generate a current cut-off between its input end and the first current branch.

[0012] Preferably, the output module is an auto transformer comprising a first winding and a second winding, wherein the first terminal of the first winding is electrically connected to the first output terminal of a rectifier circuit, the second terminal of the first winding is electrically connected to the first terminal of the second winding and used as the first terminal of a forced resonant injection circuit, and the second terminal of the second winding is electrically connected to the second output terminal of a rectifier circuit and used as the second output terminal of a forced resonant injection circuit.

[0013] Preferably, the transformer or automatic transformer is coreless.

[0014] Preferably, the polarity module comprises a first switching transistor and a second switching transistor connected to form a first bridge arm, wherein a first node formed by connecting the first and second switching transistors to each other is used as a first polarity terminal; and a third switching transistor and a fourth switching transistor connected to form a second bridge arm, wherein a second node formed by connecting the third and fourth switching transistors to each other is used as a second polarity terminal, wherein the first electrode of the first switching transistor and the first electrode of the third switching transistor are connected to the positive polarity output terminal of the rectifier circuit, and the second electrode of the second switching transistor and the second electrode of the fourth switching transistor are connected to the negative polarity output terminal of the rectifier circuit.

[0015] Preferably, the hybrid DC circuit breaker further comprises a surge arrester connected in parallel with the semiconductor switch.

[0016] When the DC power supply system is supplying power under normal conditions, the power consumption of the forced resonant injection circuit of the present invention is zero. When a fault current occurs in the DC power supply system, the forced resonant injection circuit controlsly injects a gradually increasing injection current with opposing directions into a mechanical switch, thereby allowing the current bypass time to be controlled and resulting in a low recovery voltage between the two ends of the mechanical switch, thereby enabling the mechanical switch to safely and reliably interrupt the fault current. [Brief explanation of the drawing]

[0017] Embodiments of the present invention will be further described below with reference to the attached drawings. [Figure 1] This is a block diagram of a hybrid DC circuit breaker according to a preferred embodiment of the present invention. [Figure 2] Figure 1 shows an oscillogram of the current in a hybrid DC circuit breaker. [Figure 3] Figure 1 shows a specific block diagram of the forced resonant injection circuit in the hybrid DC circuit breaker. [Figure 4] Figure 3 shows the oscillogram of the resonant current output by the resonant circuit within the forced resonant injection circuit. [Figure 5] Figure 3 shows an oscillogram of the rectified current output by the rectifier circuit within the forced resonant injection circuit. [Figure 6] Figure 3 shows an oscillogram of the injected current output by the output module in the forced resonant injection circuit. [Figure 7] This is a specific circuit diagram of a hybrid DC circuit breaker according to the first embodiment of the present invention. [Figure 8] This is a specific circuit diagram of a polarity module in a hybrid DC circuit breaker according to a second embodiment of the present invention. [Figure 9] This is a specific circuit diagram of an output module in a hybrid DC circuit breaker according to a third embodiment of the present invention. [Figure 10]This is a specific circuit diagram of a semiconductor switch in a hybrid DC circuit breaker according to a fourth embodiment of the present invention. [Figure 11] This is a specific circuit diagram of an inverter in a hybrid DC circuit breaker according to a fifth embodiment of the present invention. [Modes for carrying out the invention]

[0018] To further clarify the object, technical solution, and advantages of the present invention, the present invention will be described in more detail below through specific embodiments with reference to the accompanying drawings.

[0019] Figure 1 is a block diagram of a hybrid DC circuit breaker according to a preferred embodiment of the present invention. As shown in Figure 1, the hybrid DC circuit breaker 1 includes 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 includes terminals 1461 and 1462. Terminal 1461 of the forced resonant injection circuit 14 is connected to one end of the semiconductor switch 13. The other end of the semiconductor switch 13 and terminal 1462 of the forced resonant injection circuit 14 are connected to the two ends of the mechanical switch 11. The hybrid DC circuit breaker 1 further includes a surge arrester 12 connected in parallel to the semiconductor switch 13.

[0020] To facilitate the following explanation, the current I in the mechanical switch 11 SW , current I in surge arrester 12 A , current I in semiconductor switch 13 B , the current I output by the forced resonant injection circuit 14 C , current I in hybrid DC breaker 1 CB These are indicated by the arrows in Figure 1.

[0021] The forced resonant injection circuit 14 gradually increases the injection current I C It is controlled to output the following: Injection current I flowing to the mechanical switch 11 Cis the current I in the mechanical switch 11 SW and has a direction opposite to the direction of the current I in the mechanical switch 11 SW and is used to gradually decrease the current I in the mechanical switch 11 to zero within a predetermined commutation time.

[0022] Figure 2 is an oscillogram of the current in the hybrid DC circuit breaker shown in Figure 1. As shown in Figure 2, before time point t1, the DC power system is in a normal power supply state. There is no fault current in the circuit. The mechanical switch 11 is in the on state, and the semiconductor switch 13 is in the off state. The DC power system usually supplies power to a load (not shown in Figure 1) using the mechanical switch 11 that is normally on. In this case, the current I A in the surge arrester 12, the current I B in the semiconductor switch 13, and the injection current I C output by the forced resonance injection circuit 14 are all zero, and the current I SW in the mechanical switch 11 is equal to the current I CB 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 during normal power supply is zero.

[0023] At time point t1, when the load is short-circuited, the current I SW in the mechanical switch 11 increases rapidly, and the current I CB in the hybrid DC breaker 1 increases rapidly.

[0024] At time point t2, when the current I SW in the mechanical switch 11 increases to the tripping current, the control device or the trip circuit (not shown in Figure 1) starts to control the mechanical switch 11 to switch off.

[0025] From time point t2 to time point t3, the contacts of the mechanical switch 11 are in the separation process. The current I SW in the mechanical switch 11 gradually increases. The current I CBIt will gradually increase.

[0026] At time t3, the semiconductor switch 13 is controlled to turn on, and simultaneously at time t3, the forced resonant injection circuit 14 injects the injection current I C It is controlled to start outputting the injected current I. C The current flows from terminal 1461 to terminal 1462, and current I in the mechanical switch 11 SW It is injected into the mechanical switch 11 in the opposite direction to the direction mentioned above.

[0027] From time point t3 to time point t4, the injection current I output by the forced resonant injection circuit 14 C The current I in the semiconductor switch 13 gradually increases. B It gradually increases. Injection current I C The direction is the current I in the mechanical switch 11. SW It is in the opposite direction, and as a result, the current I in the mechanical switch 11 SW However, it gradually decreases. In this process, the current I in the mechanical switch 11 SW The current gradually bypasses the semiconductor switch 13, and the current I in the semiconductor switch 13 B and current I in hybrid DC circuit breaker 1 CB It continues to increase.

[0028] At time t4, the current I in the mechanical switch 11 SW It is zero. In this case, the current bypass process is complete. The injected current I output by the forced resonant injection circuit 14. C This is equal to zero. Current injection to the mechanical switch 11 is stopped.

[0029] From time t4 to time t5, the short-circuit current flows only through the ON semiconductor switch 13. In this case, the current I of the semiconductor switch 13 B The current I in the hybrid DC circuit breaker 1 continues to increase. CBThe force gradually increases. In this process, the moving contacts of the mechanical switch 11 continue to open at a speed of several meters per second, and the distance between the moving contacts and the static contacts reaches a predetermined contact pitch at time t5. The injected current I output by the forced resonant injection circuit 14 C As a result, the current I in the mechanical switch 11 SW The current is diverted into the semiconductor switch 13, and as a result, in this process, the mechanical switch 11 does not withstand large current interruptions, that is, it does not need to switch off with a large current. Specifically, the mechanical switch 11 can switch off with zero current and can switch off without causing any arcing.

[0030] At time t5, the control device (not shown in Figure 1) controls the semiconductor switch 13 to be in the off state or switch-off state, and the current I in the semiconductor switch 13 B It decreases to zero. In this case, the current I in the hybrid DC circuit breaker 1 CB It is the maximum.

[0031] From time t5 to time t6, since there is no potential zero crossing in the DC power system, in this case the residual electrical energy in the DC power system is discharged by the surge arrester 12 and terminals 1461 and 1462 of the forced resonant injection circuit 14, and the surge arrester 12 begins to consume the electrical energy in the DC power system. Therefore, the current I in the surge arrester 12 A It gradually decreases to zero, and at the same time, current I in the hybrid DC circuit breaker 1 CB However, it gradually decreases to zero. Finally, at time t6, the fault is cleared.

[0032] In the hybrid DC circuit breaker 1 of the present invention, the two terminals 1461 and 1462 of the forced resonant injection circuit 14 and the semiconductor switch 13 are connected in series on the second current branch and not on the first current branch where the mechanical switch 11 is located. As a result, in a normal power supply or DC transmission process, the DC power supply system uses only the mechanical switch 11 to supply power to the load, and the power consumption of the forced resonant injection circuit 14 is zero.

[0033] In addition, in the process of switching the mechanical switch 11 to the OFF position, the forced resonant injection circuit 14 of the present invention injects current I into the mechanical switch 11. SW Conversely, a gradually increasing injection current I C The current I in the mechanical switch 11 can be controlled and injected from time t3 to time t4. SW The current can be controlled to be bypassed by the semiconductor switch 13. In other words, the current bypass time can be controlled.

[0034] The forced resonant injection circuit 14, at the end of current bypass time t4, has current I in the semiconductor switch 13. B The rate of change of current can be controlled. A small rate of change of current allows the mechanical switch 11 to switch off quickly and reduces switching off losses. At the end of the current bypass t4 (i.e., time t4), the recovery voltage between the two ends of the mechanical switch 11 is equal to the resistance of the semiconductor switch 13 and the current I in the semiconductor switch 13. B Depending on the circumstances, the recovery voltage between the two ends of the mechanical switch 11 can be as low as a few volts to tens of volts. At the end of the current bypass, the mechanical switch 11 has a small rate of current change, and the recovery voltage between the two ends of the mechanical switch 11 is low, so as a result the mechanical switch 11 can switch off safely and reliably.

[0035] The period from time t4 to time t5 is the turn-off delay time of the hybrid DC circuit breaker 1, and is used to allow the distance between the moving contacts and static contacts of the mechanical switch 11 to reach a predetermined contact pitch within the turn-off delay time. The predetermined contact pitch and turn-off delay time depend on the recovery voltage of the mechanical switch 11 and the opening speed of the moving contacts.

[0036] When the hybrid DC circuit breaker 1 is used in a bidirectional DC power supply system, for example, if the direction of the current in the hybrid DC circuit breaker 1 is current I CB When the direction is opposite to that, the forced resonant injection circuit 14 is controlled to output a gradually increasing injection current to its terminal 1461.

[0037] Figure 3 shows a specific block diagram of the forced resonant injection circuit in the hybrid DC circuit breaker shown in Figure 1. As shown in Figure 3, the forced resonant injection circuit 24 includes a DC power supply 241 and DC bus capacitor C1 connected between the 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. The output terminal of the inverter 242 is connected to the input terminal of the rectifier circuit 244 using the resonant circuit 243. The output terminal of the rectifier circuit 244 is connected to the input terminal of the polarity module 245. 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 the terminal of a semiconductor switch 23, and the other terminal 2462 is connected to the terminal of a mechanical switch 21.

[0038] The DC power supply 241 is powered by the DC voltage of the first current branch or an external power supply to charge the DC bus capacitor C1. The DC bus capacitor C1 provides current to the forced resonant injection circuit using the DC bus.

[0039] The equivalent resistors, equivalent capacitors, and equivalent inductors of inverter 242, resonant circuit 243, rectifier circuit 244, polarity module 245, and output module 246 form an under-damp resonant circuit.

[0040] A control device (not shown in Figure 3) provides the inverter 242 with a high-frequency (10-100 kHz, etc.) pulse-width modulated signal, i.e., a switching pulse, which causes the inverter 242 to convert the DC current on the DC bus capacitor C1 into an AC current, i.e., a periodic square wave voltage pulse with alternating polarity, the frequency of which depends on the resonant frequency of the under-damp resonant circuit, and the resonant circuit 243 generates a resonant current I RES Outputs.

[0041] The output module 246 is further configured to generate a current disconnection between its input terminal and the first current branch.

[0042] Figure 4 is an oscillogram of the resonant current output by the resonant circuit in the forced resonant injection circuit shown in Figure 3. As shown in Figure 4, the resonant current I RES The resonant current is an alternating current with a gradually increasing amplitude, and its resonant frequency depends on the intrinsic frequencies of the inductor, capacitor, and equivalent resistors (such as bulk resistors for the inductor and capacitor) of the equivalent load circuit. At the start of oscillation, the inverter 242 outputs a voltage to the resonant circuit 243, so the resonant circuit 243 begins to generate the oscillating current. Resonant current I RES Each time the voltage crosses the zero point, the inverter 242 is controlled to switch the output voltage polarity, and the electrical energy on the DC bus capacitor C1 is output to the resonant circuit 243 using the inverter 242 to provide electrical energy within each switching cycle, resulting in the resonant current I output by the resonant circuit 243. RES The amplitude gradually increases.

[0043] The rectifier circuit 244 receives the resonant current I output by the resonant circuit 243. RES It is used to rectify the current into a pulsating DC current.

[0044] Figure 5 is an oscillogram of the rectified current output by the rectifier circuit in the forced resonant injection circuit shown in Figure 3. As shown in Figure 5, the rectified current I R This is a pulsating DC current that has a constant current direction and periodically increases its amplitude.

[0045] The polarity module 245 includes a positive polarity input terminal, a negative polarity input terminal, polarity terminal 2451, and polarity terminal 2452. The positive polarity input terminal and negative polarity input terminal of the polarity module 245 are connected to the positive polarity output terminal and negative polarity output terminal of the rectifier circuit 244, respectively. The polarity module 245 can controllably make its polarity terminals 2451 and 2452 into positive polarity output terminals and negative polarity output terminals, or into negative polarity output terminals and positive polarity output terminals. Therefore, the polarity module 245 outputs a pulsating DC current that has the same or opposite phase as the pulsating DC current output by the rectifier circuit 244.

[0046] The output module 246 is used to filter or reduce the AC components in the pulsating DC current output by the polarity module 245, thereby outputting a smooth DC current with a gradually increasing amplitude.

[0047] Figure 6 is an oscillogram of the injection current output by the output module in the forced resonant injection circuit shown in Figure 3. As shown in Figure 6, the injection current I output by the output module 246 C This is a smooth DC current, and its amplitude gradually increases over time. Injection current I C The current is output from terminal 2462 of output module 246 and flows into mechanical switch 21, resulting in the current in mechanical switch 21 gradually decreasing to zero within the current bypass time.

[0048] A high-frequency (e.g., 10-100 kHz) pulse-width modulated signal is supplied to the inverter 242, and as a result, the output module 246 can output a smooth DC current that gradually increases within a few cycles of the switching frequency (e.g., within tens to hundreds of microseconds), thus allowing fault current in the mechanical switch 21 to be quickly diverted to the semiconductor switch 23.

[0049] In another embodiment of the present invention, when the hybrid DC circuit breaker 2 is used in a unidirectional DC power supply system, the hybrid DC circuit breaker 2 does not need to have a polarity module 245, and the semiconductor switch 23 may be a unidirectional controllable semiconductor switch.

[0050] Figure 7 is a specific circuit diagram of a hybrid DC circuit breaker according to a first embodiment of the present invention. As shown in Figure 7, the semiconductor switch 33 is a bidirectionally controllable switch and includes an insulated-gate bipolar transistor T31 having an antiparallel diode and an insulated-gate bipolar transistor T32 having an antiparallel diode. The emitter of the insulated-gate bipolar transistor T31 is connected to the emitter of the insulated-gate bipolar transistor T32. Unidirectional conduction of DC current is achieved by controlling either the insulated-gate bipolar transistor T31 or T32 to be turned ON.

[0051] Inverter 342 is a full-bridge inverter consisting of four field-effect transistors.

[0052] The resonant circuit 343 includes an inductor L3 and a capacitor C3 connected in series with each other. By selecting an inductor L3 and a capacitor C3 having suitable parameters,

number

[0053] The switching frequency of inverter 342 depends on the resonant frequency of the under-damp resonant circuit. For example, when a 150μH inductor L3 and an 82nF capacitor C3 are selected, the switching frequency of inverter 342 is:

number

[0054] When two diagonal insulated-gate bipolar transistors in the inverter 342 are controlled to turn on, the DC power supply 341 outputs electrical energy using the two on diagonal insulated-gate bipolar transistors, and as a result, the resonant circuit 343 outputs a current of the first polarity. When two other diagonal insulated-gate bipolar transistors in the inverter 342 are controlled to turn on, the DC power supply 341 outputs electrical energy using the two on diagonal insulated-gate bipolar transistors, and as a result, the resonant circuit 343 outputs a current of the second polarity with an increased amplitude. The insulated-gate bipolar transistors in the inverter 342 are alternately controlled in the two aforementioned ways so that the resonant circuit 343 outputs an alternating current with a gradually increasing amplitude within multiple switching periods of the pulse-width modulated signal.

[0055] The rectifier circuit 344 is a full-wave rectifier circuit and includes four diodes.

[0056] The polarity module 345 includes a full-bridge circuit controlled to change the polarity of the input and output currents of the polarity module. Specifically, the polarity module 345 includes four insulated-gate bipolar transistors T33, T34, T35, and T36 having antiparallel diodes, and diodes D33, D34, D35, and D36 connected in series with the insulated-gate bipolar transistors T33, T34, T35, and T36. The insulated-gate bipolar transistors T33 and diode D33 connected in series with each other, and the insulated-gate bipolar transistors T34 and diode D34 connected in series with each other, are connected to each other to form node N1, which is used as polarity terminal 3451 of the polarity module 345, and the insulated-gate bipolar transistors T35 and diode D35 connected in series with each other, and the insulated-gate bipolar transistors T36 and diode D36 connected in series with each other, are connected to each other to form node N2, which is used as polarity terminal 3452 of the polarity module 345. When diagonally insulated gate bipolar transistors T33 and T36 are controlled to turn on, polarity terminals 3451 and 3452 are used as the positive and negative output terminals of polarity module 345, respectively. When diagonally insulated gate bipolar transistors T34 and T35 are controlled to turn on, polarity terminals 3451 and 3452 are used as the negative and positive output terminals of polarity module 345, respectively.

[0057] The output module 346 is an autotransformer, which is coreless to prevent magnetic saturation. The autotransformer includes windings L31 and L32. The dotted terminal of winding L31 is connected to node N1. The dotted terminal of winding L32 and the opposite polarity terminal of winding L31 are connected to each other and used as terminal 3461 of output module 346. The opposite polarity terminal of winding L32 is connected to node N2 and used as terminal 3462 of output module 346.

[0058] The polarity terminal 3452 of the polarity module 345 outputs a current I31, and when the current I31 flows to the opposite polarity terminal of winding L32, the current I31 flows from the opposite polarity terminal of winding L31 to its dotted terminal. The current I32 exists from the dotted terminal of winding L32 to its opposite polarity terminal. Terminal 3462 receives the injected current I C Outputs the injected current I. C This is equal to the sum of current I31 and current I32. Injection current I C This is injected into the mechanical switch 31, resulting in a current I in the mechanical switch 31. SW It gradually decreases to zero within a predetermined current bypass time.

[0059] Figure 8 is a specific circuit diagram of a polarity module in a hybrid DC circuit breaker according to a second embodiment of the present invention. As shown in Figure 8, the polarity module 445 includes four insulated-gate bipolar transistors T43, T44, T45, and T46 that do not have antiparallel diodes. Insulated-gate bipolar transistors T43 and T44 are connected to form a bridge arm, and insulated-gate bipolar transistors T45 and T46 are connected to form another bridge arm. Specifically, the collectors of insulated-gate bipolar transistors T43 and T45 are connected to each other and used to connect to the positive polarity output terminal of the rectifier circuit. The emitters of insulated-gate bipolar transistors T44 and T46 are connected to each other and used to connect to the negative polarity output terminal of the rectifier circuit. Node N41, formed by connecting the emitter of insulated-gate bipolar transistor T43 and the collector of insulated-gate bipolar transistor T44 to each other, is used as one polarity terminal 4451 of the polarity module 445. Node N42, formed by connecting the emitter of insulated-gate bipolar transistor T45 and the collector of insulated-gate bipolar transistor T46 to each other, is used as the other polarity terminal 4452 of polarity module 445.

[0060] When the diagonal insulated-gate bipolar transistors T43 and T46 are controlled to be ON and the insulated-gate bipolar transistors T44 and T45 are controlled to be OFF, polarity terminals 4451 and 4452 are used as positive and negative output terminals, respectively. Current flows out from polarity terminal 4451 and into polarity terminal 4452. When the other diagonal insulated-gate bipolar transistors T44 and T45 are controlled to be ON and the insulated-gate bipolar transistors T43 and T46 are controlled to be OFF, polarity terminals 4451 and 4452 are used as negative and positive output terminals, respectively. Current flows out from polarity terminal 4452 and into polarity terminal 4451.

[0061] Figure 9 is a specific circuit diagram of an output module in a hybrid DC circuit breaker according to a third embodiment of the present invention. As shown in Figure 9, the output module 446 is a coreless transformer and includes a primary winding L41 and a secondary winding L42. The dotted terminal and opposite polarity terminal of the primary winding L41 are used to connect to the positive and negative polarity output terminals of the rectifier circuit 244, respectively, or to two polarity terminals 2451 and 2452 of the polarity module 245. The dotted terminal and opposite polarity terminal of the secondary winding L42 are used as output terminals 4461 and 4462, respectively, and are used to connect to a semiconductor switch and a mechanical switch, respectively. When current flows from the opposite polarity terminal to the dotted terminal of the primary winding L41, the current in the secondary winding L42 flows from output terminal 4461 to output terminal 4462. The coreless transformer 446 has a galvanic isolation function and high-frequency resonant current I RES This also reduces the power consumption caused by the transmission of data.

[0062] Figure 10 is a specific circuit diagram of a semiconductor switch in a hybrid DC circuit breaker according to a fourth embodiment of the present invention. As shown in Figure 10, the semiconductor switch 43 includes a bridge circuit formed by connecting four diodes D41, D42, D43, and D44, and an insulated-gate bipolar transistor T41 having a collector connected to the negative terminals of diodes D41 and D43, and an emitter connected to the positive terminals of diodes D42 and D44. When the insulated-gate bipolar transistor T41 is controlled to turn on, in one conduction path, current flows in through terminal 431, through diode D41, the insulated-gate bipolar transistor T41 which is turned on, and diode D44, and flows to terminal 432. In the other conduction path, current flows in through terminal 432, through diode D43, the insulated-gate bipolar transistor T41 which is turned on, and diode D42, and flows to terminal 431.

[0063] Figure 11 is a specific circuit diagram of an inverter in a hybrid DC circuit breaker according to a fifth embodiment of the present invention. As shown in Figure 11, the inverter 442 is a half-bridge inverter and includes insulated-gate bipolar transistors T47 and T48 and capacitors C41 and C42. The positive and negative input terminals of the half-bridge inverter 442 are electrically connected to the positive and negative terminals of the DC power supply 241, respectively, and the half-bridge inverter 442 is used to convert the DC current output by the DC power supply 241 into AC current. The half-bridge inverter 442 has only two switching transistors, thereby reducing device cost.

[0064] In other embodiments of the present invention, the inverter may also be a single-level, two-level, or multi-level full-bridge (H-bridge) inverter.

[0065] In another embodiment of the present invention, a switching transistor such as a metal-oxide-semiconductor field-effect transistor (MOSFET) may be used instead of the insulated-gate bipolar transistor in the semiconductor switch 33 and / or polarity module 345 in the above embodiment.

[0066] In another embodiment of the present invention, the hybrid DC circuit breaker may include a plurality of semiconductor switches 33 connected in series with respect to one another.

[0067] In another embodiment of the present invention, the rectifier circuit 244 may be a half-wave rectifier circuit that rectifies an alternating current into a pulsating direct current.

[0068] Although the present invention has been described by preferred embodiments, the present invention is not limited to the embodiments described herein and includes various modifications and variations that do not depart from the scope of the invention.

Claims

1. It is a hybrid DC circuit breaker, A mechanical switch connected to the first current branch, A semiconductor switch and a forced resonant injection circuit connected to a second current branch, wherein the forced resonant injection circuit comprises a first terminal and a second terminal, the first terminal of the forced resonant injection circuit is 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 are connected to two ends of the mechanical switch, characterized in that the semiconductor switch and the forced resonant injection circuit comprise a semiconductor switch and a forced resonant injection circuit. When the mechanical switch is in the process of being switched off, the semiconductor switch is controlled to be turned on, and at the same time, the forced resonant injection circuit is controlled to inject a gradually increasing injection current into the mechanical switch in the opposite direction to the current in the mechanical switch, so that the current in the mechanical switch gradually decreases to zero within a predetermined bypass time, and the current is bypassed from the first current branch to the second current branch. The forced resonant injection circuit, A DC power supply, which is powered by the DC voltage of 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 supply current to the forced resonant injection circuit, An inverter is provided with switching pulses during current injection to generate periodic square wave voltage pulses with alternating polarity. A resonant circuit comprising an inductor and a capacitor connected in series with each other, having one end connected to the output terminal of the inverter and the other end used to output an alternating current having a gradually increasing amplitude, A rectifier circuit having an input terminal connected to the other end of the resonant circuit and an output terminal used to output a pulsating DC current having a gradually increasing amplitude, An output module having an input terminal electrically connected to the output terminal of the rectifier circuit, and an output terminal used as the first and second terminals of the forced resonant injection circuit, wherein the output module is used to filter and amplify the pulsating DC current and to output the injected current, A hybrid DC circuit breaker in which the inverter, the resonant circuit, and the equivalent resistor, equivalent inductor, and equivalent capacitor of the circuit connected between the other end of the resonant circuit and the output end of the inverter form an underdamp resonant circuit, and the frequency of the periodic square wave voltage pulse depends on the resonant frequency of the underdamp resonant circuit.

2. The hybrid DC circuit breaker according to claim 1, wherein the forced resonant injection circuit is controlled to stop outputting the injected current when the current in the mechanical switch decreases to zero within the predetermined bypass time.

3. The hybrid DC circuit breaker according to claim 2, wherein the semiconductor switch is controlled to turn off when the contact pitch of the mechanical switch reaches a predetermined threshold.

4. The semiconductor switch is a semiconductor switch that can be controlled in both directions. The hybrid DC circuit breaker according to any one of claims 1 to 3, further comprising a polarity module connected between the rectifier circuit and the output module, wherein the polarity module comprises a full-bridge circuit controlled to change the polarity of the input current and output current of the polarity module.

5. The hybrid DC circuit breaker according to any one of claims 1 to 3, wherein the inverter is a single-level, two-level, or multi-level full-bridge inverter, or a half-bridge inverter.

6. The hybrid DC circuit breaker according to any one of claims 1 to 3, wherein the output module is configured to be a transformer for generating a current disconnection between its input terminal and the first current branch.

7. The output module is an auto transformer comprising a first winding and a second winding, wherein the first terminal of the first winding is electrically connected to the first output terminal of the rectifier circuit, the second terminal of the first winding is electrically connected to the first terminal of the second winding and used as the first terminal of the forced resonant injection circuit, and the second terminal of the second winding is electrically connected to the second output terminal of the rectifier circuit and used as the second output terminal of the forced resonant injection circuit, the hybrid DC circuit breaker according to any one of claims 1 to 3.

8. The hybrid DC circuit breaker according to claim 6 or 7, wherein the transformer or the auto-transformer is coreless.

9. The aforementioned polarity module A first switching transistor and a second switching transistor connected to form a first bridge arm, wherein a first node formed by connecting the first switching transistor and the second switching transistor to each other is used as a first polarity terminal, A third switching transistor and a fourth switching transistor connected to form a second bridge arm, wherein a second node formed by connecting the third switching transistor and the fourth switching transistor to each other is used as a second polarity terminal, comprising: The hybrid DC circuit breaker according to claim 4, wherein the first electrode of the first switching transistor and the first electrode of the third switching transistor are connected to the positive polarity output terminal of the rectifier circuit, and the second electrode of the second switching transistor and the second electrode of the fourth switching transistor are connected to the negative polarity output terminal of the rectifier circuit.

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

Images