CN116742576A - Low-cost serial hybrid circuit breaker - Google Patents
Low-cost serial hybrid circuit breaker Download PDFInfo
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- CN116742576A CN116742576A CN202310138723.7A CN202310138723A CN116742576A CN 116742576 A CN116742576 A CN 116742576A CN 202310138723 A CN202310138723 A CN 202310138723A CN 116742576 A CN116742576 A CN 116742576A
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- 239000003990 capacitor Substances 0.000 claims abstract description 91
- 230000008878 coupling Effects 0.000 claims abstract description 89
- 238000010168 coupling process Methods 0.000 claims abstract description 89
- 238000005859 coupling reaction Methods 0.000 claims abstract description 89
- 238000002347 injection Methods 0.000 claims abstract description 86
- 239000007924 injection Substances 0.000 claims abstract description 86
- 238000004146 energy storage Methods 0.000 claims abstract description 77
- 238000004804 winding Methods 0.000 claims description 61
- 230000009471 action Effects 0.000 claims description 11
- 230000001965 increasing effect Effects 0.000 claims description 9
- 230000008859 change Effects 0.000 claims description 8
- 230000003044 adaptive effect Effects 0.000 claims description 4
- 230000007423 decrease Effects 0.000 claims description 4
- 230000003071 parasitic effect Effects 0.000 claims description 4
- 238000010586 diagram Methods 0.000 description 9
- 238000000034 method Methods 0.000 description 6
- 238000013461 design Methods 0.000 description 4
- 238000006243 chemical reaction Methods 0.000 description 3
- 230000000694 effects Effects 0.000 description 3
- 230000008569 process Effects 0.000 description 3
- 238000013459 approach Methods 0.000 description 2
- 230000033228 biological regulation Effects 0.000 description 2
- 238000011161 development Methods 0.000 description 2
- 238000007599 discharging Methods 0.000 description 2
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- 238000012986 modification Methods 0.000 description 2
- 230000009467 reduction Effects 0.000 description 2
- 230000004044 response Effects 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 230000001939 inductive effect Effects 0.000 description 1
- 238000002955 isolation Methods 0.000 description 1
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- 239000002184 metal Substances 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 238000010248 power generation Methods 0.000 description 1
- HBMJWWWQQXIZIP-UHFFFAOYSA-N silicon carbide Chemical compound [Si+]#[C-] HBMJWWWQQXIZIP-UHFFFAOYSA-N 0.000 description 1
- 229910010271 silicon carbide Inorganic materials 0.000 description 1
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Classifications
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H3/00—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection
- H02H3/08—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to excess current
- H02H3/087—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to excess current for dc applications
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H3/00—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection
- H02H3/02—Details
- H02H3/021—Details concerning the disconnection itself, e.g. at a particular instant, particularly at zero value of current, disconnection in a predetermined order
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
- H02H7/26—Sectionalised protection of cable or line systems, e.g. for disconnecting a section on which a short-circuit, earth fault, or arc discharge has occured
- H02H7/268—Sectionalised protection of cable or line systems, e.g. for disconnecting a section on which a short-circuit, earth fault, or arc discharge has occured for dc systems
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Abstract
The application discloses a low-cost serial hybrid circuit breaker, which comprises a main branch module and a voltage injection circuit module, wherein the circuit injection circuit module is used for generating multi-level injection voltage, realizing ultra-fast fault interruption and creating a zero-current operation window for a mechanical switch; according to the application, by introducing an auxiliary coupling inductor, the generation of multi-level injection voltage by a single energy storage capacitor is realized, and the pre-charging of the energy storage capacitor in the serial hybrid circuit breaker is simplified; in addition, the operation characteristics of the voltage injection circuit are fully analyzed, part of the full-control type power devices are replaced by half-control type power devices, the breaker is optimally designed, the current level of only the full-control type power devices is reduced, the cost of the power devices is reduced, and the cost of the series-connection type hybrid breaker is greatly reduced by simplifying the pre-charging link of the energy storage capacitor and reducing the number and the current level of the full-control type power devices.
Description
Technical Field
The application relates to the technical field of power equipment, in particular to a low-cost serial hybrid circuit breaker which is suitable for fault protection of a direct current power system.
Background
With the development of technologies such as distributed new energy power generation and electric automobiles, a direct current micro-grid becomes one of the trend and direction of future development. The direct current circuit breaker plays an important role in fault isolation, equipment switching and topology reconstruction, and is a key device of a direct current micro-grid.
Dc circuit breakers are generally classified into mechanical, solid state, and hybrid types. The hybrid circuit breaker has the advantages of low on-state loss and high on-off speed. However, hybrid circuit breakers rely on the arc voltage of the mechanical switch to force the fault current to be diverted from the mechanical leg to the commutation leg, limiting the fault interrupting speed to some extent, and the arc also shortens the useful life of the mechanical switch. A converter switch (power device) is added to be connected with a mechanical switch in series, when a fault occurs, the converter switch is turned on, fault current is quickly transferred to a converter branch, fault interruption speed can be remarkably improved, and on-state loss of the converter switch is not negligible. The current injection circuit is added in the current conversion branch, fault current can be quickly converted to the current conversion branch, so that fault interruption speed is improved, and on-state loss of the current conversion switch is effectively avoided. However, the hybrid circuit breaker is of a "parallel type", and during fault interruption, the fault current still continues to increase through the parallel commutation branches, and the fault interruption speed is difficult to further increase.
The document "Coupled Inductor-Based Zero Current Switching Hybrid DC Circuit Breaker Topologies" reports a hybrid circuit breaker in which a coupling Inductor is connected in series with a mechanical switch, and injection voltage generated by the coupling Inductor forces fault current to drop to zero rapidly, and the mechanical switch is opened in a zero-crossing point of the current in an arc-free manner, so that the hybrid circuit breaker has a rapid fault interruption speed and low on-state loss. However, the circuit breaker needs to accurately turn on a mechanical switch when a current passes through a zero point, and a voltage injection circuit based on a thyristor can not be continuously adjusted, so that only one current passes through the zero point. The document A Series-Type Hybrid Circuit Breaker (S-HCB) Concept for Ultrafast DC Fault Protection formally proposes the concept of a Series-type hybrid circuit breaker, two fully-controlled power devices and two energy storage capacitors with different voltage levels endow the voltage injection circuit with repeated adjustment capability, the fault current can be quickly reduced, the fault current is adjusted to be in a high-frequency alternating current ripple state, and the zero-current opening of a mechanical switch does not need precise timing control. The series hybrid circuit breaker has the advantages of high response speed, low on-state loss, no arc opening of a mechanical switch and the like, and has great application prospect.
However, the precharge of the fully controlled power devices and the storage capacitor in the voltage injection circuit also results in a significant increase in the cost of the series hybrid circuit breaker. On the one hand, compared with the half-control type power device with the same specification, the price of the full-control type power device is greatly increased, so that the cost of the power device of the series hybrid circuit breaker is greatly increased, and if the silicon carbide device with high price is used, the cost problem of the power device is further worsened. On the other hand, the voltage levels of the two energy storage capacitors are greatly different, so that the charging device of the energy storage capacitors is required to output two paths of voltages with different voltage levels, and the influence of the specific charging device on the cost of the series type hybrid circuit breaker cannot be ignored.
Therefore, the cost reduction of the series hybrid circuit breaker has important significance for large-scale popularization and application.
Disclosure of Invention
The application aims to solve the technical problems of providing a low-cost serial hybrid circuit breaker aiming at the defects of the prior art, solves the problem of the rapid increase of cost caused by the precharge of a full-control power device and an energy storage capacitor in a voltage injection circuit, and is suitable for the fault protection of a direct current power system.
In order to solve the technical problems, the application provides a low-cost series hybrid circuit breaker, which at least can ensure that the voltage injection regulation function of the series hybrid circuit breaker can be realized by only needing a fully-controlled power device and an energy storage capacitor, and the technical scheme adopted by the application is as follows:
the embodiment of the application provides a low-cost serial hybrid circuit breaker, which comprises a main branch module and a voltage injection circuit module;
the main branch module comprises a mechanical switch, a current limiting inductor and a secondary winding of a main coupling inductor;
the voltage injection circuit module comprises a full-control type power device, a half-control type power device, a diode, an energy storage capacitor, an auxiliary coupling inductor and a primary winding of the main coupling inductor, and the main branch module is connected with the voltage injection circuit module through the main coupling inductor;
the energy storage capacitor is used for generating two levels of injection voltage so as to enable the main branch current to drop to zero under the condition that the main branch current of the main branch module is larger than or equal to an action threshold value, the mechanical switch is opened in an arc-free mode, and the voltage of the energy storage capacitor is enabled to drop to zero.
In some embodiments, the diode comprises a first diode and a second diode, the mechanical switch, the current limiting inductor and the secondary winding of the primary coupling inductor are connected in sequence,
one end of the energy storage capacitor is connected with the secondary winding of the auxiliary coupling inductor and the first diode through a half-control power device, and is connected with the primary winding of the auxiliary coupling inductor and the second diode through the full-control power device;
the other end of the energy storage capacitor is respectively connected with the first diode, the second diode, the primary winding of the auxiliary coupling inductor and one end of the primary winding of the main coupling inductor, and the other end of the primary winding of the main coupling inductor is connected with the secondary winding of the auxiliary coupling inductor.
In some embodiments, the series hybrid circuit breaker has the following operation modes when an open-circuit fault occurs:
mode I: the mechanical switch is closed, the voltage injection circuit is closed, and the main branch current of the main branch module is smaller than an action threshold;
modality ii: after the main branch circuit breaking and short-circuiting fault occurs, the main branch current of the main branch module is rapidly increased;
mode III: when the main branch current of the main branch module is larger than or equal to an action threshold value, the voltage injection circuit is started, and the semi-control power device and the full-control power device are conducted so as to enable the main branch current to drop;
modality iv: the half-control type power device is conducted, the full-control type power device is disconnected, and a primary winding of the auxiliary coupling inductor and the diode form a follow current path so as to increase the current of the main branch;
modality V: the mechanical switch is disconnected, the semi-control type power device and the full-control type power device are conducted, so that the energy storage capacitor is communicated with the secondary winding of the main coupling inductor through the semi-control type power device and the full-control type power device, and the energy storage capacitor discharges, so that the reverse voltage at the mechanical switch is reduced;
mode VI: the mechanical switch is disconnected, the semi-controlled power device is connected, the full-controlled power device is disconnected, so that the energy storage capacitor is communicated with the auxiliary coupling inductor through the diode and the semi-controlled power device, and the energy storage capacitor discharges, so that the voltage of the energy storage capacitor drops to zero.
In some embodiments, the fully controlled power device of the series hybrid circuit breaker switches between an on state and an off state to cause the main shunt module to open the mechanical switch to cause the series hybrid circuit breaker to switch at high frequency between mode iii and mode iv such that the main shunt current drops to zero, the mechanical switch opening.
In some embodiments, the voltage injection circuit module controls the fully-controlled power device to switch between an on state and an off state, so that the energy storage capacitor provides an injection voltage of a first level in the on state of the fully-controlled power device, and provides an injection voltage of a second level in the off state of the fully-controlled power device, so that the main shunt current is in a high-frequency alternating-current ripple state and is reduced to zero.
In some embodiments, the injection voltage of the first level is greater than the corresponding dc system voltage of the primary shunt module, the injection voltage of the first level being used to reduce the primary shunt current;
the injection voltage of the second level is smaller than the direct current system voltage, and the injection voltage of the second level is used for being matched with the injection voltage of the first level, modulating the main shunt current into a high-frequency alternating current ripple state and reducing the main shunt current to zero.
In some embodiments, the first level of injection voltage is expressed as: n is n 2 U C +n 2 n 1 U C Wherein U is C For storing capacitor voltage, n 1 For the turn ratio of the secondary coil to the primary coil of the auxiliary coupling inductor, n 2 A secondary to primary turn ratio for the primary coupled inductor;
the injection voltage of the second level is expressed as: n is n 2 U C 。
In some embodiments, n 1 、n 2 Primary winding L of auxiliary coupling inductance 11 Secondary winding L 12 Primary winding L of main coupling inductance 21 And a secondary winding L 22 The following relationship is satisfied:
when the series hybrid circuit breaker is in a mode II, the main coupling inductance and the secondary side voltage u 22 DC system voltage U dc Rate of change di of main shunt current 2 dT, current limiting inductance L 3 And parasitic inductance L 4 The following relationship is satisfied:
in some embodiments, the series hybrid circuit breaker pre-charges the storage capacitor after mode i and/or mode vi in a manner that includes independent charging circuit charging and adaptive charging circuit charging.
In some embodiments, the adaptive charging circuit includes a thyristor for controlling the energy storage capacitor to precharge and a current limiting resistor for controlling the precharge speed of the energy storage capacitor.
The series hybrid circuit breaker realizes that the current of the main branch is approximately zero by switching between the mode III and the mode IV at high frequency, thereby creating conditions for the zero current opening of the mechanical switch of the main branch; meanwhile, the application realizes that a single energy storage capacitor generates two-level injection voltage by adding an auxiliary coupling inductor, thereby realizing rapid interruption of faults and reducing the number of the energy storage capacitors; the application only adopts the full-control power device for controlling the auxiliary coupling inductance, reduces the number of the full-control power devices, and reduces the current level of the full-control power device by optimally designing the design parameters of the series hybrid circuit breaker.
Compared with the prior art, the application has the beneficial effects that at least the following steps are included:
1. according to the application, by adding the auxiliary coupling inductor, the single energy storage capacitor can generate two-level injection voltage, so that the rapid interruption of faults is realized, the number of the energy storage capacitors is reduced, and the pre-charging process of the energy storage capacitors is simplified.
2. In the application, only the auxiliary coupling inductor is controlled by adopting the fully-controlled power device, so that the number of the fully-controlled power devices is reduced, and the cost of the power devices is further effectively reduced.
3. According to the application, through optimizing the design parameters of the series hybrid circuit breaker, the current level of the fully-controlled power device is reduced, and the cost of the power device is further reduced.
Drawings
FIG. 1 is a topological structure diagram of a low cost series hybrid circuit breaker of the present application;
fig. 2 is a key waveform diagram of the low-cost serial hybrid circuit breaker of the present application when an open-circuit fault occurs;
FIG. 3 is a schematic diagram of the operation mode of the low-cost series hybrid circuit breaker of the present application when an open-circuit fault occurs;
fig. 4 is a schematic diagram of two start-up operating schemes of a low cost series hybrid circuit breaker of the present application.
Detailed Description
The present application will be described in further detail with reference to the drawings and examples, in order to make the objects, technical solutions and advantages of the present application more apparent. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the application.
In some embodiments, although functional block division is performed in a system diagram, logical order is shown in a flowchart, in some cases, steps shown or described may be performed in a different order than block division in a system, or in a flowchart. The terms first, second and the like in the description and in the claims and in the above-described figures are used for distinguishing between similar objects and not necessarily for describing a particular sequential or chronological order.
In the prior art, in order to quickly cut off faults of a direct current system and realize arc-free opening of a mechanical switch, a plurality of energy storage capacitors and a plurality of full-control power devices are introduced into the mechanical switch of the series hybrid circuit breaker, and the cost of the series hybrid circuit breaker is greatly increased due to higher manufacturing cost of the full-control power devices and the energy storage capacitors, so that the reduction of the cost of the series hybrid circuit breaker has important significance for large-scale popularization and application of the series hybrid circuit breaker.
In order to solve at least the technical problems, the application provides a low-cost serial hybrid circuit breaker, which at least can ensure that the voltage injection adjusting function of the serial hybrid circuit breaker can be realized only by a fully-controlled power device and an energy storage capacitor, so as to solve the problem of the rapid increase of the cost caused by the pre-charging of the fully-controlled power device and the energy storage capacitor in a voltage injection circuit, and is suitable for the fault protection of a direct current power system.
Specific embodiments of the present application will be described in detail below with reference to fig. 1 to 4 and table 1.
FIG. 1 is a schematic diagram of the present application, in some embodiments, the present application includes a main branch module 1 and a voltage injection circuit module 2, where T 1 And T 2 The main coupling inductance and the auxiliary coupling inductance are respectively. The main branch module 1 comprises a mechanical switch S 1 Current limiting inductance L 3 And T 2 Inductance L of secondary winding of (2) 22 . The voltage injection circuit module 2 comprises a full-control power device Q 2 Semi-controlled power device Q 1 Diode D 1 Diode D 2 Storage capacitor C, T 2 Inductance L of primary winding of (2) 21 T is as follows 1 . Wherein U is C For storing capacitor voltage, u 11 And u is equal to 21 Respectively T 1 And T is 2 Primary side voltage of u 12 And u is equal to 22 Respectively T 1 And T is 2 Is set in the voltage domain of the battery. i.e 2 I for the current through the main branch 11 And i 21 Respectively by T 1 And T is 2 The current of the primary winding.
The energy storage capacitor is used for generating multi-level injection voltage so as to enable the main branch current to drop to zero and realize the arc-free opening of the mechanical switch under the condition that the main branch current of the main branch module is larger than or equal to the action threshold value.
In some embodiments, the voltage injection circuit module is configured to control the semi-controlled power device to be turned on when the mechanical switch is turned on and the main branch current of the main branch module is greater than or equal to the short-circuit current threshold, and control the fully-controlled power device to switch between an on state and an off state, so that the energy storage capacitor generates multi-level injection voltage, the main branch current drops to zero, and the arc-free opening of the mechanical switch in the main branch module is realized; after the mechanical switch is disconnected by the main branch module, the voltage injection circuit module is used for controlling the full-control power device and the half-control power device to be turned off, so that the voltage of the energy storage capacitor is reduced to zero, and the energy of the main coupling inductor and the auxiliary coupling inductor is reduced to zero; the application not only maintains the advantages of quick interruption speed and low on-state loss of the conventional series hybrid circuit breaker, but also simplifies the starting operation of the series hybrid circuit breaker, and can realize the voltage injection regulation function of the series hybrid circuit breaker only by using one full control type power device and one energy storage capacitor, thereby effectively reducing the cost of the power device.
In some embodiments, the diode comprises a first diode and a second diode, the mechanical switch, the current-limiting inductor and the secondary winding of the main coupling inductor are sequentially connected, one end of the energy storage capacitor is connected with the secondary winding of the auxiliary coupling inductor and the first diode through the half-control type power device, and is connected with the primary winding of the auxiliary coupling inductor and the second diode through the full-control type power device; the other end of the energy storage capacitor is respectively connected with the first diode, the second diode, the primary winding of the auxiliary coupling inductor and one end of the primary winding of the main coupling inductor, and the other end of the primary winding of the main coupling inductor is connected with the secondary winding of the auxiliary coupling inductor.
Specifically, referring to fig. 1, the present application includes a main branch module 1 and a voltage injection circuit module 2, wherein the main branch module 1 includes a mechanical switch S 1 Current limiting inductance L 3 And main coupling inductance T 2 Secondary winding L of (2) 22 The method comprises the steps of carrying out a first treatment on the surface of the The voltage injection circuit module 2 comprises a full-control power device Q 2 Semi-controlled power device Q 1 First diode D 1 And a second diode D 2 An energy storage capacitor C and an auxiliary coupling inductance T 1 And main coupling inductance T 2 Primary winding L of (2) 21 The method comprises the steps of carrying out a first treatment on the surface of the The connection relationship is as follows: mechanical switch S 1 Current limiting inductance L 3 And main coupling inductance T 2 Secondary winding L of (2) 22 The positive electrode of the energy storage capacitor C is connected in sequence through a semi-controlled power device Q 1 And auxiliary coupling inductance T 1 Secondary winding L of (2) 12 And a first diode D 1 Connected through a fully-controlled power device Q 2 And auxiliary coupling inductance T 1 Primary winding L of (2) 11 And a second diode D 2 Are connected; negative electrode of energy storage capacitor CThe ends are respectively connected with the first diode D 1 Second diode D 2 Auxiliary coupling inductance T 1 Primary winding L of (2) 11 And main coupling inductance T 2 Primary winding L of (2) 21 Is connected with the positive terminal of the main coupling inductance T 2 Primary winding L of (2) 21 Is coupled with the auxiliary coupling inductance T at the negative terminal 1 Secondary winding L of (2) 12 Are connected.
In some embodiments, n 1 And n 2 Respectively T 1 And T is 2 The secondary to primary turn ratio of (2) satisfy the following relationship:
in some embodiments, the mechanical switch S in the main branch is in the event of a short-circuit failure of the corresponding DC system of the main branch module 1 Current limiting inductance L 3 Parasitic inductance L of line in normal operation 4 Parasitic inductance L 'from short-circuit fault point to circuit breaker' 4 And main coupling inductance T 2 Secondary winding L of (2) 22 The voltages of the components satisfy the following relationship:
wherein di 2 Dt is the main shunt current i 2 Rate of change of U dc Is the voltage of the direct current system.
In some embodiments, the auxiliary coupling inductance T 1 With main coupling inductance T 2 The voltage and current of (a) satisfy the following relationship:
wherein di 11 Dt is auxiliary coupling inductanceSecondary side current i 11 Rate of change, di 12 The/dt is the primary side current i of the main coupling inductance 12 Rate of change of M 1 And M 2 Respectively T 1 And T 2 Is a mutual inductance of (a). The coupling inductors are used for transmitting injection power, T 1 And T 2 Can be designed as a fully coupled inductor. Thus M 1 And M 2 Can be expressed as:
in some embodiments, to ensure the normal operation of the series hybrid circuit breaker of the present application, the injection voltage of the present application needs to have a level satisfying equation (6):
injection voltage level (n) 2 U C +n 2 n 1 U C ) Greater than the voltage (U) of the DC system dc ) The method is used for forcing the fault current to drop rapidly, and is a key point of the ultra-rapid fault interruption speed. Injection voltage level (n) 2 U C ) Less than the voltage of the DC system (U dc ) For interfacing with injection voltage level (n 2 U C +n 2 n 1 U C ) In the application, under the condition of adding an auxiliary coupling inductance, only one capacitor and one controlled power device can be used for generating two-level injection voltage (two injection voltages with different levels are realized by switching on and off of a full-controlled power device Q2, n) 2 U C +n 2 n 1 U C And n 2 U C ) The number of the energy storage capacitors is further reduced, and the starting operation of the series hybrid circuit breaker is simplified; the parameters of the series hybrid circuit breaker are optimally designed, so that the advantages of high interruption speed and low on-state loss of the conventional series hybrid circuit breaker are maintained, and the conventional series hybrid circuit breaker is reducedThe cost of the power devices of the series hybrid circuit breaker.
In some embodiments, when the main branch has a short-circuit fault, the application has six working modes from mode i to mode VI, fig. 2 shows a key waveform diagram of the application when the short-circuit fault is interrupted, fig. 3 shows the working mode of the application when the short-circuit fault is interrupted, and according to formulas (1) - (5), the change rates of key currents of mode iii and mode iv in the application are shown in table (1):
watch (1)
Table (1) is a table of the rate of change of the critical currents of modes III and IV in the present application, wherein U S1 Is S 1 The voltage, i th For the protection action threshold of the proposed breaker, U dc Is the voltage of a direct current bus, R L Is a load.
When an open-short fault occurs, the detailed working principle of the application is as follows:
the main branch current of the main branch module is smaller than the action threshold, the main branch normally operates, the mechanical switch is closed, and the voltage injection circuit is closed: t is t 1 Before the moment, the system normally operates, S 1 On, the voltage injection circuit is in an off state, and the operation mode is mode I, as shown in fig. 3 (a). i.e 2 The flow path comprises only windings (L 22 、L 3 、L 4 ) And mechanical switch (S) 1 ) The application has low on-state loss.
After the main branch circuit breaking and short-circuiting fault occurs, the main branch current of the main branch module is rapidly increased: at t 1 At the moment, a short-circuit fault occurs, i 2 The mode of operation is mode II, as shown in fig. 3 (b).
Main shunt current is larger than action threshold, voltage injection circuit is started, semi-controlled power device andthe fully controlled power device is turned on to reduce the main shunt current: at t 2 Time, i 2 Reaching the protection action threshold i th ，Q 1 And Q is equal to 2 Conduction is performed, and the working mode is a mode III, as shown in fig. 3 (c). According to Table (1) and formula (6), di can be obtained 2_Ⅲ /dt<0 force i 2 And rapidly drops.
The semi-controlled power device is conducted, the fully-controlled power device is disconnected, and a primary winding of the auxiliary coupling inductor and the diode form a follow current path so as to increase the current of the main branch: at t 3 At the moment, the fault current drops to zero, Q 1 Conduction, Q 2 Shut off, L 11 And D 2 A freewheel path is configured, and its operation mode is mode IV, as shown in fig. 3 (d). According to Table (1) and formula (6), di can be obtained 2_Ⅳ /dt>0, fault current i 2 And (3) increasing. t is t 3 ≤t＜t 4 During the period Q 2 High frequency switch, the proposed circuit breaker switches between mode III and mode IV, i 2 Modulated to an alternating current ripple close to zero, expands S 1 Is provided.
The mechanical switch is disconnected, and the half-control power device and the full-control power device are connected, so that the reverse voltage at the mechanical switch is reduced: at t 4 Time of day, S 1 Disconnection, Q 1 Conduction, Q 2 Shut off, L 11 And D 2 A freewheel path is formed, and its operation mode is a mode V, as shown in fig. 3 (e).
The mechanical switch is disconnected, the semi-control type power device is conducted, and the full-control type power device is disconnected, so that the voltage of the energy storage capacitor is reduced to zero: when the energy storage capacitor passes through Q 1 、L 12 、L 21 Continuing to discharge U C Falling to zero, automatically switching to mode VI, L as shown in FIG. 3 (f) 11 And D 2 Form a follow current path L 21 、L 12 、D 1 A freewheeling circuit is formed and the energy stored by the inductor is dissipated in the windings and the internal resistance of the diode.
According to the working principle, the multi-level voltage injection can be realized by only a single energy storage capacitor, so that the number of the energy storage capacitors is reduced, and the pre-charging process of the energy storage capacitors is simplified.
In some embodiments, the mechanical switch S in the low-cost series hybrid circuit breaker of the present application is referred to as modality I in FIG. 3 under normal operation of the primary-side corresponding system, i.e., before the primary-side fails in an open-circuit or short-circuit condition 1 On, the voltage injection circuit module is turned off, and the main branch corresponds to normal operation of the system and corresponds to t in FIG. 2 0 ≤t＜t 1 During which the main branch current i 2 L in the flow path 22 、L 3 、L 4 Corresponding to metal wire, S 1 The low-cost series hybrid circuit breaker has the characteristic of low on-state loss, and the main branch corresponds to the normal operation of the system.
In some embodiments, the on-off condition in the low cost series hybrid circuit breaker in modality ii corresponds to modality i when the main branch fails in an open circuit, corresponding to t in fig. 2 1 Short-circuit fault occurs at moment, main branch current i 2 Rapidly increasing.
In some embodiments, according to table 1 and equation (6) above, di2_iii/dt <0, i2 is reduced. Corresponding to the period t2 < t3 in fig. 2, that is, the mode III, the fault current decreases from the protection operation threshold ith to zero, that is, the main branch circuit i2 decreases and approaches 0 when the energy storage capacitor provides the injection voltage of the first level in the on state of the fully controlled power device.
In some embodiments, the fully controlled power device of the series hybrid circuit breaker switches between an on state and an off state to cause the main branch module to open the mechanical switch to cause the series hybrid circuit breaker to switch at high frequency between mode iii and mode iv such that the main branch current drops to zero and the mechanical switch opens.
In some embodiments, the voltage injection circuit module controls the fully-controlled power device to switch between an on state and an off state, so that the energy storage capacitor provides an injection voltage of a first level in the on state of the fully-controlled power device, and provides an injection voltage of a second level in the off state of the fully-controlled power device, so that the main branch current is in a high-frequency alternating-current ripple state and is reduced to zero.
Specifically, at this time, corresponding to the mode iv in fig. 3, the on-off condition in the low-cost serial hybrid circuit breaker is as follows: q (Q) 1 Conduction, Q 2 Shut off, L 11 And D 2 Form a follow current path, u 11 ＝0，u 12 +u 21 ＝U C According to the above formulas (1), (2), (3), (4) and (5), the change rate of the key current such as i2 in the mode is shown in the table (1), and di can be obtained according to the table (1) and the formula (6) 2_Ⅳ /dt>0，i 2 And (3) increasing. Corresponding to t in FIG. 2 3 ≤t＜t 4 During the period Q 2 High frequency switch, the proposed circuit breaker switches between mode III and mode IV to achieve i 2 Approximately equal to 0, S 1 The zero current opening creates the condition, namely the energy storage capacitor provides the injection voltage of the second level in the state that the full-control type power device is turned off in the mode IV, and corresponds to the mode III, so that the main branch current is in a high-frequency alternating current ripple state and finally approaches to 0 by controlling the on-off of the half-control type power device, and the cost of the serial circuit breaker is effectively reduced while the application has the advantages of high response speed, low on-state loss, no arc opening of a mechanical switch and the like.
In some embodiments, the injection voltage of the first level is greater than the corresponding dc system voltage of the primary shunt module, the injection voltage of the first level being used to reduce the primary shunt current; the injection voltage of the second level is smaller than the direct current system voltage, and the injection voltage of the second level is used for being matched with the injection voltage of the first level, so that the main shunt current is modulated into a high-frequency alternating current ripple state and is reduced to zero; corresponding formula (6), n 2 U C +n 2 n 1 U C I.e. the injection voltage of the first level, n 2 U C I.e., the injection voltage at the second level.
In some embodiments, the low-cost serial hybrid circuit breaker is switched from an on state to an off state by controlling the fully-controlled power device, so that the energy storage capacitor discharges through the primary windings of the half-controlled power device, the auxiliary coupling inductor and the main coupling inductor, and the voltage of the energy storage capacitor drops to zero; the half-control type power device is turned off, so that a first winding of the auxiliary coupling inductor and the second diode form a follow current loop, a first winding of the main coupling inductor, a second winding of the auxiliary coupling inductor, the first diode and the second diode form a follow current loop, and the energy of the main coupling inductor and the energy of the auxiliary coupling inductor are reduced to zero.
In some embodiments, after the main branch module turns off the mechanical switch, the voltage injection circuit module is used for controlling the semi-controlled power device and the fully-controlled power device to be conducted so that the energy storage capacitor is communicated with the secondary winding of the main coupling inductor through the semi-controlled power device and the fully-controlled power device, and the energy storage capacitor discharges, so that the reverse voltage at the mechanical switch is reduced; specifically, the mode V, S in FIG. 3 corresponds to 1 Disconnection, Q 1 And Q is equal to 2 Conduction, S 1 Is subjected to a small reverse voltage (U S1 ＝U dc -n 2 (1+n 1 )U C < 0). Corresponding to t in FIG. 2 4 ≤t＜t 5 During the period, the capacitor is continuously discharged to reverse the voltage U S1 Gradually decrease, thereby realizing the effect of reducing the reverse voltage.
In some embodiments, the voltage injection circuit module is used for controlling the conduction of the half-control type power device, and the full-control type power device is turned off, so that the energy storage capacitor is communicated with the auxiliary coupling inductor through the second diode and the half-control type power device, and the energy storage capacitor discharges, so that the voltage of the energy storage capacitor drops to zero; specifically, S 1 Disconnection, Q 1 And Q is equal to 2 Shut off, L 11 And D 2 Form a follow current path L 21 、L 12 、D 1 Forming a freewheel loop. The energy stored by the inductor is consumed on the internal resistances of the winding and the diode, so that the voltage energy clearing effect of the energy storage capacitor is realized.
In some embodiments, the low-cost series hybrid circuit breaker switches from an on state to an off state by controlling the fully-controlled power device to discharge the energy storage capacitor through the primary windings of the half-controlled power device, the auxiliary coupling inductor and the main coupling inductor and to reduce the voltage of the energy storage capacitor to zero, and comprises controlling the half-controlled power device and the fully-controlled power device to conduct to communicate the energy storage capacitor with the secondary winding of the main coupling inductor through the half-controlled power device and the fully-controlled power device, and discharging the energy storage capacitor to reduce the reverse voltage at the mechanical switch; and controlling the semi-controlled power device to be conducted, and switching off the full-controlled power device so as to enable the energy storage capacitor to be communicated with the auxiliary coupling inductor through the second diode and the semi-controlled power device, and discharging the energy storage capacitor, so that the voltage of the energy storage capacitor is reduced to zero.
According to the circuit design and formulas (1) to (6) in the embodiment, the application is converted between the modes I to VI, so that the design parameters of the auxiliary coupling inductor and the main coupling inductor in the application can be effectively optimized, the current level of the fully-controlled power device is reduced, the advantages of high interruption speed and low on-state loss of the conventional series hybrid circuit breaker are maintained, the starting operation process of the series hybrid circuit breaker is simplified, and the cost of the series hybrid circuit breaker is further reduced.
In some embodiments, FIG. 4 illustrates two start-up operating schemes of the present application. The independent charging circuit scheme is shown in the left circuit diagram in fig. 4, and can be classified into wired charging and wireless charging, and the following prior art documents can be referred to for specific implementation schemes:
[1]High-Frequency High Step-Up Inductive Power Transfer-Based Capacitor Charger in Active Injection DC Circuit Breakers；
[2]HVDC Circuit Breakers Combining Mechanical Switches and a Multilevel PWM Converter:V erification by Downscaled Models；
[3]Multiphase Interleaved IPT Based Current-Source Converter for High-Current Application。
in this scheme, the charging voltage of the energy storage capacitor is in a specific proportional relationship with the voltage of the direct current system, and the relationship can be determined by the formula (6). When the voltage of the direct current system fluctuates greatly, the output voltage of the charging circuit needs to be correspondingly adjusted so as to ensure that the application can normally operate. The scheme of the self-adaptive charging circuit is shown in the circuit diagram on the right side in FIG. 4, and the thyristor Q 3 Opening during pre-charging, and automatically charging the energy storage capacitorClosing, charging speed can be changed by changing current-limiting resistor R 1 To adjust. In this scheme, the voltage of the storage capacitor is equal to the voltage of the DC system, which can be controlled by controlling the thyristor Q 3 Is easy to implement. Therefore, by adopting the self-adaptive charging circuit scheme, the reliability of the application is improved, and the application has great potential in medium-low voltage application.
According to formula (3), i 11 Slope di of (d) 11 Dt can be expressed as
di 11 /dt＝u 11 /L 11 +n 1 ·(di 12 /dt) (7)
During fault interruption, u 11 Is equal to zero for most of the time, and a larger L can be selected 11 ，u 11 /L 11 Pair i 11 The effect of the slope of (c) is small. So i 11 Is of slope of approximately i 21 N of slope 1 Multiple times. i.e 11max Is i 11 Is determined by the maximum value of Q 1 And D 1 Is set to be a rated current of (1); i.e 21max Is i 21 Is determined by the maximum value of Q 2 And D 2 Is set in the above range). Due to i 11 And i 21 All increase from zero, so i 11max /i 21max Is also approximately equal to n 1 . And n is 1 Is the turn ratio of the auxiliary coupling inductance, which satisfies n 1 <<1. Therefore, the application not only reduces the number of the full-control power devices, but also reduces the current level of only the full-control power devices, and effectively controls the device cost.
The application realizes the injection of multi-level voltage by only using a single energy storage capacitor by adding an auxiliary coupling inductor, reduces the number of the energy storage capacitors and simplifies the pre-charging of the serial hybrid breaker.
According to the application, by analyzing the operation characteristics of the voltage injection circuit in the series hybrid circuit breaker, part of the fully-controlled power devices are replaced by the low-cost half-controlled power devices, the current level of the only fully-controlled power devices is optimized, and the cost of the power devices is reduced.
In some embodiments, the switching states of the full-control power device, the half-control power device and the mechanical switch are determined by the received external driving signal or the driving signal sent by the controller, and the driving signal can be sent out through an analog circuit or an embedded chip.
The above is only a preferred embodiment of the present application, and is not intended to limit the present application, but various modifications and variations can be made to the present application by those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application are included in the protection scope of the present application.
Claims (10)
1. The low-cost serial hybrid circuit breaker is characterized by comprising a main branch circuit module and a voltage injection circuit module;
the main branch module comprises a mechanical switch, a current limiting inductor and a secondary winding of a main coupling inductor;
the voltage injection circuit module comprises a full-control type power device, a half-control type power device, a diode, an energy storage capacitor, an auxiliary coupling inductor and a primary winding of the main coupling inductor, and the main branch module is connected with the voltage injection circuit module through the main coupling inductor;
the energy storage capacitor is used for generating two levels of injection voltage so as to enable the main branch current to drop to zero under the condition that the main branch current of the main branch module is larger than or equal to an action threshold value, the mechanical switch is opened in an arc-free mode, and the voltage of the energy storage capacitor is enabled to drop to zero.
2. The low-cost series hybrid circuit breaker of claim 1, wherein the diode comprises a first diode and a second diode, the mechanical switch, the current limiting inductor and the secondary winding of the primary coupling inductor are connected in sequence,
one end of the energy storage capacitor is connected with the secondary winding of the auxiliary coupling inductor and the first diode through a half-control power device, and is connected with the primary winding of the auxiliary coupling inductor and the second diode through the full-control power device;
the other end of the energy storage capacitor is respectively connected with the first diode, the second diode, the primary winding of the auxiliary coupling inductor and one end of the primary winding of the main coupling inductor, and the other end of the primary winding of the main coupling inductor is connected with the secondary winding of the auxiliary coupling inductor.
3. The series hybrid circuit breaker of claim 1, wherein the series hybrid circuit breaker has the following modes of operation when an open-circuit fault occurs:
mode I: the mechanical switch is closed, the voltage injection circuit is closed, and the main branch current of the main branch module is smaller than an action threshold;
modality ii: after the main branch circuit breaking and short-circuiting fault occurs, the main branch current of the main branch module is rapidly increased;
mode III: when the main branch current of the main branch module is larger than or equal to an action threshold value, the voltage injection circuit is started, and the semi-control power device and the full-control power device are conducted so as to enable the main branch current to drop;
modality iv: the half-control type power device is conducted, the full-control type power device is disconnected, and a primary winding of the auxiliary coupling inductor and the diode form a follow current path so as to increase the current of the main branch;
modality V: the mechanical switch is disconnected, the semi-control type power device and the full-control type power device are conducted, so that the energy storage capacitor is communicated with the secondary winding of the main coupling inductor through the semi-control type power device and the full-control type power device, and the energy storage capacitor discharges, so that the reverse voltage at the mechanical switch is reduced;
mode VI: the mechanical switch is disconnected, the semi-controlled power device is connected, the full-controlled power device is disconnected, so that the energy storage capacitor is communicated with the auxiliary coupling inductor through the diode and the semi-controlled power device, and the energy storage capacitor discharges, so that the voltage of the energy storage capacitor drops to zero.
4. A series hybrid circuit breaker as claimed in claim 3 wherein the fully controlled power device of the series hybrid circuit breaker switches between an on state and an off state to cause the main branch module to open the mechanical switch to cause the series hybrid circuit breaker to switch at high frequency between mode iii and mode iv such that the main branch current drops to zero, the mechanical switch opening.
5. The series hybrid circuit breaker of claim 4, wherein the voltage injection circuit module controls the fully controlled power device to switch between an on state and an off state such that the storage capacitor provides an injection voltage of a first level in the fully controlled power device on state and the storage capacitor provides an injection voltage of a second level in the fully controlled power device off state such that the main shunt current is in a high frequency ac ripple state and decreases to zero.
6. The series hybrid circuit breaker of claim 5, wherein the first level of injection voltage is greater than a corresponding dc system voltage of the primary shunt module, the first level of injection voltage being used to step down the primary shunt current;
the injection voltage of the second level is smaller than the direct current system voltage, and the injection voltage of the second level is used for being matched with the injection voltage of the first level, modulating the main shunt current into a high-frequency alternating current ripple state and reducing the main shunt current to zero.
7. The series hybrid circuit breaker of claim 6, wherein the first level injection voltage is expressed as: n is n 2 U C +n 2 n 1 U C Wherein U is C For storing capacitor voltage, n 1 For the turn ratio of the secondary coil to the primary coil of the auxiliary coupling inductor, n 2 A secondary to primary turn ratio for the primary coupled inductor;
the injection voltage of the second level is expressed as: n is n 2 U C 。
8. The series hybrid circuit breaker of claim 7, wherein n 1 、n 2 Primary winding L of auxiliary coupling inductance 11 Secondary winding L 12 Primary winding L of main coupling inductance 21 And a secondary winding L 22 The following relationship is satisfied:
when the series hybrid circuit breaker is in a mode II, the main coupling inductance and the secondary side voltage u 22 DC system voltage U dc Rate of change di of main shunt current 2 dT, current limiting inductance L 3 And parasitic inductance L 4 The following relationship is satisfied:
9. a series hybrid circuit breaker according to claim 3, wherein the series hybrid circuit breaker pre-charges the storage capacitor after mode i and/or mode vi, the pre-charging means comprising independent charging circuit charging and adaptive charging circuit charging.
10. The series hybrid circuit breaker of claim 9, wherein the adaptive charging circuit comprises a thyristor for controlling the pre-charge of the storage capacitor and a current limiting resistor for controlling the pre-charge rate of the storage capacitor.
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