Direct-current switching-on and switching-off equipment adopting series resonance

Abstract

The utility model provides a direct-current on-off device adopting series resonance. The device comprises a main branch, a transfer branch and an energy consumption branch which are connected in parallel. The main branch consists of one or more quick mechanical switches which are connected in series; the transfer branch comprises LC resonance circuits and one or more power electronic switch modules which are connected in series; the power electronic switch module comprises a current bidirectional flow circuit formed by a full-control switch tube and N diodes, wherein N is an integer greater than or equal to 4; and the energy consumption branch comprises a lightning arrester. According to the utility model, load current and short-circuit current can be rapidly cut off, on-state loss can be reduced, and the reliability of the whole DC system can be improved.

Description

Technical Field

[0001] The utility model belongs to the field of electric power equipment, in particular to a DC breaking device adopting series resonance. Background Art

[0002] DC transmission and distribution refers to a method of transmission and distribution in which the AC power generated by the power plant is converted into DC power by a rectifier and transmitted to the receiving end, and then the DC power is converted into AC power by an inverter and sent to the receiving end AC power grid. The DC transmission and distribution system is mainly composed of a converter station (including a rectifier station and an inverter station), a DC line, power filters on the AC and DC sides, reactive power compensation devices, converter transformers, DC reactors, and protection and control devices. Among them, the converter station is the core of the DC transmission system, which completes the conversion between AC and DC. With the access of new energy, DC transmission and distribution has developed rapidly in recent years due to its long transmission distance, large transmission capacity, low loss, and good economy.

[0003] However, due to the characteristics of DC power transmission and distribution, it is impossible to clear the DC side fault through the converter's own control. Therefore, when a short circuit fault occurs on the DC side, it is necessary to rely on tripping the AC side switch to isolate the fault. However, the strategy of locking the converter valve and tripping the AC side switch takes a long time to clear the fault and restore the system, resulting in low fault clearing efficiency, which makes the reliability of the entire DC power transmission and distribution system low.

[0004] Therefore, safe and reliable DC circuit breakers are urgently needed in DC transmission and distribution networks to quickly cut off load current and short-circuit current and improve the reliability of the entire DC system.

[0005] Existing DC circuit breaker topologies are mainly divided into three types: hybrid DC circuit breaker, solid-state DC circuit breaker and mechanical DC circuit breaker.

[0006] The hybrid DC circuit breaker is composed of a main branch, a transfer branch and an energy-consuming branch in parallel. The main branch is composed of a fast mechanical switch and a power electronic switch in series. During normal operation, the current passes through the main branch. Due to the large on-state loss of the power electronic switch, this topology consumes more electric energy during normal operation of the system. In addition, since a large amount of heat is generated when the power electronic switch is turned on, a heat dissipation device needs to be configured for it.

[0007] The solid-state DC circuit breaker is composed of a main branch and an energy-consuming branch in parallel. The main branch is composed of fully controlled power electronic switching devices in series. Although the short-circuit current is turned off in a short time, the conduction loss is very large during normal operation.

[0008] Mechanical DC circuit breakers are also composed of a main branch, a transfer branch and an energy-consuming branch in parallel, and the transfer branch is composed of a large-capacity high-voltage capacitor and an inductor in series. Although the main branch of this topology also has no power electronic switches and the on-state loss is relatively small, the capacitance of the transfer branch configuration will increase a lot with the increase of voltage level, and its time to cut off small current faults is longer. Utility Model Content

[0009] In order to solve the deficiencies in the prior art, the utility model provides a DC disconnecting device using series resonance, which can reduce conduction loss and improve the reliability of the entire DC system while quickly cutting off load current and short-circuit current.

[0010] The utility model adopts the following technical solutions.

[0011] The utility model discloses a DC disconnecting device using series resonance. The DC disconnecting device comprises a main branch, a transfer branch and an energy consumption branch connected in parallel; the main branch is composed of one or more fast mechanical switches connected in series; the transfer branch comprises an LC resonance circuit connected in series and one or more power electronic switch modules; the power electronic switch module comprises a current bidirectional flow circuit formed by a fully controlled switch tube and N diodes, wherein N is an integer greater than or equal to 4; the energy consumption branch comprises a lightning arrester.

[0012] Furthermore, the fast mechanical switch includes a vacuum interrupter, an electromagnetic repulsion mechanism, and a driving connecting rod; the vacuum interrupter has a moving contact; the electromagnetic repulsion mechanism is used to generate electromagnetic repulsion through magnetic field interaction; one end of the driving connecting rod is connected to the moving contact, and the other end is connected to the electromagnetic repulsion mechanism, and under the action of the electromagnetic repulsion force, the moving contact is driven to move quickly to an insulation distance that can withstand a transient recovery voltage.

[0013] Furthermore, the electromagnetic repulsion mechanism is a coil-type electromagnetic repulsion mechanism.

[0014] Furthermore, the fast mechanical switch also includes a buffer and a retainer.

[0015] Furthermore, the current bidirectional flow circuit includes a first input node, a first output node, a fully controlled switch, a first diode, a second diode, a third diode and a fourth diode; the fully controlled switch includes a gate, an emitter and a collector; the gate is connected to an external control signal; the collector is connected to the cathodes of the first diode and the third diode respectively; the emitter is connected to the anode of the second diode and the anode of the fourth diode respectively; the anode of the first diode and the cathode of the fourth diode are connected to the first input node; the anode of the third diode and the cathode of the second diode are connected to the first output node.

[0016] Furthermore, the fully controlled switch tube includes but is not limited to IGCT, IGBT, and IEGT.

[0017] Furthermore, one or more of the first diode, the second diode, the third diode and the fourth diode are each connected in parallel with one or more other diodes.

[0018] Furthermore, the bidirectional current flow circuit also includes one or more other fully-controlled switching tubes connected in parallel with the fully-controlled switching tube.

[0019] Furthermore, the LC resonant circuit includes a second input node, a second output node, a first inductor, a second inductor, a capacitor, a thyristor and a fifth diode; the second input node is connected to the second output node via the second inductor and the first inductor connected in series in sequence; the positive electrode of the capacitor is connected to the positive electrode of the thyristor, the negative electrode of the capacitor is connected to the connection point of the first inductor and the second inductor, and the negative electrode of the thyristor is connected to the second output node; the positive electrode of the fifth diode is connected to the second output node, and the negative electrode of the fifth diode is connected to the positive electrode of the thyristor.

[0020] Furthermore, the arrester includes one or more MOVs connected in series and / or in parallel.

[0021] The beneficial effect of the utility model is that, compared with the prior art, a parallel main branch, a transfer branch and an energy consumption branch are set, and at the same time, the main branch is set to be composed of one or more fast mechanical switches connected in series, and the transfer branch is set to include a series-connected LC resonant circuit and one or more power electronic switch modules, wherein the power electronic switch module includes a current bidirectional flow circuit formed by a fully controlled switch tube and N diodes. In this way, when there is no fault on the line and the system operates normally, the current flows through the main branch of the DC circuit breaker. When a fault occurs on the load side of the DC line and a short-circuit current is generated, the DC circuit breaker will receive the disconnection command of the system, the main branch fast mechanical switch starts to open, and at the same time, the fully controlled switch tube in the transfer branch is turned on, and the distance between the contacts of the main branch fast mechanical switch gradually increases. After a certain period of time, through the action of the LC resonant circuit, the current begins to transfer from the main branch to the transfer branch. After waiting for the contact gap of the fast mechanical switch in the main branch to establish an insulation distance that can withstand the breaking overvoltage, the fully controlled switch tube in the transfer branch is locked, and the current begins to transfer to the energy-consuming branch and gradually decreases. Finally, all the electric energy is consumed by the energy-consuming branch, and the entire short-circuit fault breaking task is completed. According to simulation, the time from the DC circuit breaker receiving the system breaking command to the current starting to decrease is less than 3ms, which is much shorter than the time required for breaking the current by the strategy of locking the converter valve and tripping the AC side switch in the traditional DC distribution network. In addition, in the utility model, since the main branch does not include a power electronic switch, compared with the existing hybrid DC circuit breaker and solid-state DC circuit breaker including a power electronic switch, the on-state loss can be greatly reduced; and since the transfer branch includes one or more power electronic switch modules in series in addition to the LC resonant circuit, the power electronic switch can share the voltage on the transfer branch for the LC resonant circuit, so the capacitance in the LC resonant circuit in the transfer branch does not need to be greatly increased with the increase of the voltage level, thereby greatly reducing the time to cut off the small current fault compared with the existing solid-state DC circuit breaker.

[0022] In summary, the technical solution of the utility model can reduce conduction loss while quickly cutting off load current and short-circuit current, thereby improving the reliability of the entire DC system. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The utility model is further described below in conjunction with the accompanying drawings.

[0024] Figure 1 The figure is a diagram of the overall topological structure of a DC switching device using series resonance in one embodiment.

[0025] Description of reference numerals:

[0026] 1-main branch; 2-transfer branch; 3-energy consumption branch; 4-power electronic switch module; 5-LC resonance module; S-fast mechanical switch; IN1-first input node; OUT1-first output node; IN2-second input node; OUT2-second output node; G-fully controlled power electronic device; B-lightning arrester; D1-first diode; D2-second diode; D3-third diode; D4-fourth diode; D5-fifth diode; C-charging capacitor; T-thyristor; L1-first reactor; L2-second reactor. DETAILED DESCRIPTION

[0027] In order to make the purpose, technical solution and advantages of the utility model clearer, the technical solution of the utility model will be clearly and completely described below in conjunction with the drawings in the embodiments of the utility model. The embodiments described in this application are only part of the embodiments of the utility model, not all of them. Based on the spirit of the utility model, other embodiments obtained by ordinary technicians in this field without creative work are all within the scope of protection of the utility model.

[0028] like Figure 1 As shown, in one embodiment, the DC switching device using series resonance of the utility model includes a main branch 1, a transfer branch 2 and an energy consumption branch 3 connected in parallel.

[0029] The main branch 1 is composed of one or more fast mechanical switches S connected in series. The fast mechanical switch S can be closed and opened according to the received system instructions.

[0030] The transfer branch 2 is used to shut off the forward and reverse currents under various transient steady-state conditions, and includes a series-connected LC resonant circuit 5 and one or more power electronic switch modules 4. The power electronic switch module 4 includes a current bidirectional flow circuit formed by a fully controlled switch tube G and N diodes, where N is an integer greater than or equal to 4.

[0031] The energy consumption branch 3 is used to suppress transient breaking overvoltage and absorb energy stored in inductive components, and includes a lightning arrester B.

[0032] In a further preferred embodiment, the fast mechanical switch S includes a vacuum interrupter, an electromagnetic repulsion mechanism, and a driving connecting rod. The vacuum interrupter has a moving contact; the electromagnetic repulsion mechanism is used to generate electromagnetic repulsion through magnetic field interaction; one end of the driving connecting rod is connected to the moving contact, and the other end is connected to the electromagnetic repulsion mechanism, and under the action of the electromagnetic repulsion, the moving contact is driven to move quickly to an insulation distance that withstands transient recovery voltage. Wherein, the electromagnetic repulsion mechanism is a coil-type electromagnetic repulsion mechanism. More preferably, the fast mechanical switch also includes a buffer and a retainer. The buffer is used to absorb the energy of the moving parts, reduce the speed of the moving parts, and reduce and prevent the opening and closing bounce during the opening and closing process of the fast mechanical switch. The buffer can be a spring buffer, a hydraulic buffer, a material buffer, a cylinder buffer, an electromagnetic buffer, etc. The retainer is used to maintain the fast mechanical switch in the opening and closing position, and is an important element for maintaining the opening or closing state of the mechanical switch. The retainer can be a spring retainer, a permanent magnet retainer, etc.

[0033] In a further preferred embodiment, the current bidirectional flow circuit includes a first input node IN1, a first output node OUT1, a fully controlled switch G, a first diode D1, a second diode D2, a third diode D3 and a fourth diode D4; the fully controlled switch G includes a gate, an emitter and a collector; the gate is connected to an external control signal; the collector is respectively connected to the cathode of the first diode D1 and the cathode of the third diode D3; the emitter is respectively connected to the anode of the second diode D2 and the anode of the fourth diode D4; the anode of the first diode D1 and the cathode of the fourth diode D4 are connected to the first input node IN1; the anode of the third diode D3 and the cathode of the second diode D2 are connected to the first output node OUT1.

[0034] In a further preferred embodiment, the fully controlled switch tube G includes but is not limited to IGCT (Integrated Gate-Commutated Thyristor), IGBT (Insulate-Gate Bipolar Transistor), and IEGT (Injection Enhanced Gate Transistor).

[0035] In a further preferred embodiment, one or more of the first diode D1 , the second diode D2 , the third diode D3 and the fourth diode D4 are each connected in parallel with one or more other diodes.

[0036] In a further preferred embodiment, the bidirectional current flow circuit further includes one or more other fully-controlled switch tubes connected in parallel with the fully-controlled switch tube G.

[0037] In a further preferred embodiment, the LC resonant circuit includes a second input node IN2, a second output node OUT2, a first inductor L1, a second inductor L2, a capacitor C, a thyristor T and a fifth diode D5; the second input node IN2 is connected to the second output node OUT2 via the second inductor L2 and the first inductor L1 connected in series in sequence; the positive electrode of the capacitor C is connected to the positive electrode of the thyristor T, the negative electrode of the capacitor C is connected to the connection point of the first inductor L1 and the second inductor L2, and the negative electrode of the thyristor T is connected to the second output node OUT2; the positive electrode of the fifth diode D5 is connected to the second output node OUT2, and the negative electrode of the fifth diode D5 is connected to the positive electrode of the thyristor T.

[0038] In this embodiment, the resonant circuit is composed of a charging capacitor 4 for storing the initial energy of the resonance, and by turning on the thyristor T, the capacitor C, the first inductor L1 and the second inductor L2 form a series resonant circuit, thereby generating a reverse electromotive force, causing the current of the main branch 1 to pass through zero and extinguish the arc, and causing the fast mechanical switch in the main branch 1 to be disconnected (that is, the contact gap of the main branch fast mechanical switch establishes an insulation distance that can withstand the breaking overvoltage).

[0039] In a further preferred embodiment, the arrester B comprises one or more MOVs (Metal Oxide Varistors) connected in series and / or in parallel.

[0040] The working principle of the DC breaking device using series resonance of the utility model is as follows:

[0041] By installing the DC disconnecting device using series resonance in series on the DC line, when there is no fault on the line and the system is operating normally, the current flows through the main branch of the DC circuit breaker. When a fault occurs on the load side of the DC line and a short-circuit current is generated, the DC disconnecting device will receive the disconnection command of the system, the main branch fast mechanical switch starts to open, and at the same time, the transfer branch full-controlled switch tube G is turned on, and the distance between the contacts of the main branch fast mechanical switch gradually increases. After a certain period of time, the thyristor T in the LC resonant circuit is triggered, and through the action of the LC resonant circuit, the current begins to transfer from the main branch to the transfer branch. After waiting for the gap between the fast mechanical switch contacts in the main branch to establish an insulation distance that can withstand the breaking overvoltage, the transfer branch full-controlled switch tube G is locked, and the current begins to transfer to the energy-consuming branch and gradually decreases. Finally, all the electric energy is consumed by the energy-consuming branch, and the entire short-circuit fault disconnection task is completed. According to simulation, the time from when the DC circuit breaker receives the system disconnection command to when the current begins to decrease is less than 3ms, which is much shorter than the time required to disconnect the current by using the traditional DC distribution network strategy of locking the converter valve and tripping the AC side switch.

[0042] In addition, in the utility model, since the main branch does not include a power electronic switch, the conduction loss can be greatly reduced compared to the existing hybrid DC circuit breakers and solid-state DC circuit breakers that include power electronic switches; and since the transfer branch also includes one or more power electronic switch modules connected in series in addition to the LC resonant circuit, the power electronic switch can share the voltage on the transfer branch for the LC resonant circuit, so the capacitance of the LC resonant circuit in the transfer branch does not need to be greatly increased with the increase of the voltage level, thereby significantly reducing the time to cut off a small current fault compared to the existing solid-state DC circuit breaker.

[0043] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the utility model rather than to limit it. Although the utility model is described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that the specific implementation methods of the utility model can still be modified or replaced by equivalents, and any modifications or equivalent replacements that do not depart from the spirit and scope of the utility model should be included in the scope of protection of the claims of the utility model.

Claims

1. A DC switching device using series resonance, characterized in that: It includes a main branch, a transfer branch and an energy consumption branch connected in parallel; The main branch is composed of one or more fast mechanical switches connected in series; The transfer branch includes an LC resonant circuit and one or more power electronic switch modules connected in series; the power electronic switch module includes a current bidirectional flow circuit formed by a fully controlled switch tube and N diodes, wherein N is an integer greater than or equal to 4; The energy consumption branch includes a lightning arrester.

2. The DC switching device using series resonance according to claim 1 is characterized in that: The fast mechanical switch includes a vacuum interrupter, an electromagnetic repulsion mechanism, and a driving connecting rod; The vacuum interrupter chamber has a moving contact; The electromagnetic repulsion mechanism is used to generate electromagnetic repulsion through magnetic field interaction; One end of the driving connecting rod is connected to the moving contact, and the other end is connected to the electromagnetic repulsion mechanism, and under the action of the electromagnetic repulsion, the moving contact is driven to move quickly to an insulation distance that withstands transient recovery voltage.

3. The DC switching device using series resonance according to claim 2 is characterized in that: The electromagnetic repulsion mechanism is a coil type electromagnetic repulsion mechanism.

4. The DC switching device using series resonance according to claim 2, characterized in that: The fast mechanical switch also includes a buffer and a retainer.

5. The DC switching device using series resonance according to claim 1, characterized in that: The current bidirectional flow circuit includes a first input node, a first output node, a fully controlled switch, a first diode, a second diode, a third diode and a fourth diode; The fully controlled switch includes a gate, an emitter and a collector; the gate is connected to an external control signal; the collector is connected to the cathode of the first diode and the cathode of the third diode respectively; the emitter is connected to the anode of the second diode and the anode of the fourth diode respectively; the anode of the first diode and the cathode of the fourth diode are connected to the first input node; the anode of the third diode and the cathode of the second diode are connected to the first output node.

6. The DC switching device using series resonance according to claim 5, characterized in that: The fully controlled switch tube includes IGCT, IGBT or IEGT.

7. The DC switching device using series resonance according to claim 5, characterized in that: One or more of the first diode, the second diode, the third diode and the fourth diode are each further connected in parallel with one or more other diodes.

8. The DC switching device using series resonance according to claim 5, characterized in that: The bidirectional current flow circuit also includes one or more other fully-controlled switching tubes connected in parallel with the fully-controlled switching tube.

9. The DC switching device using series resonance according to claim 1, characterized in that: The LC resonant circuit includes a second input node, a second output node, a first reactor, a second reactor, a capacitor, a thyristor and a fifth diode; The second input node is connected to the second output node via the second inductor and the first inductor connected in series in sequence; the positive electrode of the capacitor is connected to the positive electrode of the thyristor, the negative electrode of the capacitor is connected to the connection point of the first inductor and the second inductor, and the negative electrode of the thyristor is connected to the second output node; the positive electrode of the fifth diode is connected to the second output node, and the negative electrode of the fifth diode is connected to the positive electrode of the thyristor.

10. The DC switching device using series resonance according to claim 1, characterized in that: The arrester includes one or more MOVs connected in series and / or in parallel.

Images