CN114362113A - Coupling inductance type bidirectional direct current limiter with direct current distribution network grounding bypass function - Google Patents
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Abstract
A coupling inductance type bidirectional direct current limiter with a direct current distribution network grounding bypass function belongs to the field of direct current transmission protection equipment. The invention aims to design a coupling inductance type bidirectional direct current limiter which aims at realizing the function of efficiently inhibiting the direct current fault current from being grounded and bypassed in a direct current distribution network. The method comprises the following steps: designing the topology of GBCIB-FCL, designing four working states of the GBCIB-FCL topology, establishing a model of the GBCIB-FCL topology current limiting process, and providing a method for selecting main parameters of the GBCIB-FCL. The coupling inductance type bidirectional direct current limiter with the grounding bypass function is scientific and reasonable, strong in applicability, high in reliability and good in effect.
Description
Technical Field
The invention belongs to the field of direct-current power transmission protection equipment.
Background
With the increase in the problem of energy shortage and environmental deterioration, the development and utilization of energy are gradually shifting from conventional energy to renewable energy. The direct current power grid with the technical advantage of flexible direct current transmission is an effective means for renewable energy source grid connection and consumption. The use of overhead lines for networking of the direct-current power grid is a mainstream form in the future, but the overhead lines also bring more risks of faults to the direct-current power grid. Because a direct current power grid formed by power electronic devices has the characteristics of low inertia and low impedance, the fault development is rapid, so that the fault current can reach the upper limit of the working tolerance of an Insulated Gate Bipolar Transistor (IGBT) and related power electronic devices within milliseconds, and huge hidden dangers are caused to the safe operation of a direct current system, particularly a direct current converter station. And the direct current system current has no zero crossing point, which brings new challenges for the efficient suppression of fault current. From the viewpoint of avoiding the locking exit of the converter station, the addition of the direct current fault current limiter is an effective means for inhibiting the fault current.
Disclosure of Invention
The invention aims to design a coupling inductance type bidirectional direct current limiter which aims at realizing the function of efficiently inhibiting the direct current fault current from being grounded and bypassed in a direct current distribution network.
The method comprises the following steps:
s1 designing topology of GBCIB-FCL
GBCIB-FCL is composed of main current part and current limiting partQuick mechanical switch BrkFCLAnd load transfer switch connected in series, when short circuit fault occurs in the system, the short circuit current transfer is realized by switching in current-limiting part, which comprises auxiliary branch, current-limiting branch and bypass branch, the auxiliary branch is parallel IGBT solid switch SFCLThe current-limiting branch circuit utilizes the characteristics of low frequency of passing inductance, high frequency of resistance and quick controllability of full control devices to convert direct current fault current into high-frequency alternating current, and the bypass branch circuit is a thyristor valve group TbyAnd a shunt resistor RbyThe auxiliary branch, the current limiting branch and the bypass branch realize the bidirectional power exchange of GBCIB-FCL through a diode bridge;
s2 designing four working states of normal-pre-limiting flow-disconnecting bypass of GBCIB-FCL topology
(1) When the DC line is in normal operation, BrkFCLAnd LCS closed conduction, SFCLOff, SL1、SL2Turning off;
(2) when GBCIB-FCL is in the pre-restricted flow working state, giving SFCLTurn on signal to simultaneously give SL1、SL2Alternately turn on the signal and then turn off BrkFCLLCS, GBCIB-FCL enters into the pre-current-limiting working state, and the current in the current limiter flows through the auxiliary branch;
(3) to give SFCLOff signal, SL1、SL2Keep alternately conducting and trigger TbyThe current in the current limiter flows through the current limiting branch circuit, the shunt resistor and the coupling inductor;
(4)BrkFCLbreaking, SFCLOff, SL1、SL2Off, triggered TbyThe valve group puts the bypass branch into a direct current inductor to provide an energy leakage loop, and the current in the GBCIB-FCL mainly flows through the bypass branch;
s3, establishing model of GBCIB-FCL topology current limiting process
Suppose that S is nowL1Off, SL2Conducting, neglecting other nonlinear devices in the current limiting part, taking a relevant reference direction, and obtaining an equivalent circuit:
arranging formula (1) into a matrix form:
taking the state variable x ═ iL1 iL2 iL)TThe input U ═ U, lists the equation of state:
wherein:
in the same way, when SL1Conducting SL2Similar results can be obtained when switching off;
s4 method for selecting main parameters of GBCIB-FCL
The parameters to be designed include inductance L1And L2Mutual inductance k and alternate signal frequency fswTaken from the induction of L ═ L1＝L2Changing from 50mH to 150mH in steps at 25mH, and changing the mutual inductance k from 0 to 1 in steps at 0.1 interval to obtain the condition that the short-circuit current is limited when the current limiting part works alone, and taking the frequency f of the alternate signalswThe resulting fault current waveform was stepped from 1.5kHz to 3.5kHz at 0.25 kHz.
The coupling inductance type bidirectional direct current limiter with the grounding bypass function is scientific and reasonable, strong in applicability, high in reliability and good in effect.
Drawings
FIG. 1 is a topology diagram of a GBCIB-FCL;
FIG. 2 is a diagram of the normal operating state of the GBCIB-FCL;
FIG. 3 is a diagram of the pre-qualified flow operating state of the GBCIB-FCL;
FIG. 4 is a diagram of the current limiting operating state of the GBCIB-FCL;
FIG. 5 is a state diagram of the disconnect bypass of the GBCIB-FCL;
FIG. 6 is a mathematical model equivalent circuit diagram of GBCIB-FCL;
FIG. 7 is a graph of short circuit current conditions for the sole operation of the current limiting section when the self-inductance is varied from 50mH to 150mH and the mutual inductance is varied from 0 to 1;
FIG. 8 is a graph of the short circuit current condition for the current limiting section operating alone with an increase in the alternating signal frequency of 1.5kHz to 3.5 kHz.
Detailed Description
The method comprises the following steps:
step 1: designing the topology of GBCIB-FCL;
step 2: designing four working states of 'normal-pre-current limiting-disconnection bypass' of a GBCIB-FCL topology;
and step 3: establishing a mathematical model of a GBCIB-FCL topology current limiting process;
and 4, step 4: the main parameter selection method of GBCIB-FCL is given.
The topology of the GBCIB-FCL is shown in FIG. 1, where the GBCIB-FCL is composed of a main current flow portion and a current limit portion. The main current part (branch) is composed of a fast mechanical switch BrkFCLAnd a Load Communication Switch (LCS) in series, and the on-state loss of the LCS is low, so that the power transmission during the normal operation of the system is maintained. When the system has short-circuit fault, the transfer of short-circuit current is realized by inputting a current-limiting part, and the part consists of an auxiliary branch, a current-limiting branch and a bypass branch. Auxiliary branch namely parallel IGBT solid state switch SFCLThe main current branch circuit is used for matching with a main current branch circuit to transfer fault current, and matching with a direct current breaker to carry out reclosing operation after current transfer. In the current-limiting branch circuit, the characteristics of low frequency and high frequency resistance of an inductor and quick and controllable full-control devices are utilized to convert the direct-current fault current into high-frequency alternating current so as to realize the purpose of quick and efficient suppression of the direct-current fault current. Energy dissipation resistor RL1、RL2For coupling an inductance L1、L2Providing a discharge loop; inductance IGBT solid state switch SL1、SL2Through and shunt resistor RFCLPartial fault current shunting is realized in parallel connection; protective lightning arrester AL1、AL2And peak absorbing arrester aFCLThe device is used for absorbing peak overvoltage in the action process of the switching tube and preventing breakdown and damage of the device caused by overvoltage at two ends of a switching device (IGBT). Bypass branchRouting thyristor valve group TbyAnd a shunt resistor RbyThe series connection structure can bypass the inductor on the fault side to realize fault isolation. The auxiliary branch, the current limiting branch and the bypass branch realize the bidirectional power exchange of the GBCIB-FCL through a diode bridge.
And designing four working states of 'normal-pre-current limiting-disconnection bypass' of the GBCIB-FCL topology.
The normal operating state of GBCIB-FCL is shown in FIG. 2. When the DC line is in normal operation, BrkFCLAnd LCS closed conduction, SFCLOff, SL1、SL2And (6) turning off. The current in the current limiter flows through the main current branch, and the current limiting part is BrkFCLBy-pass, the current path is as shown in figure 1. Because the current does not flow through a switching device, a diode or a resistor, the low loss of the GBCIB-FCL in normal operation is ensured.
The pre-qualified flow operating state of the GBCIB-FCL is shown in FIG. 3. When GBCIB-FCL is in the pre-restricted flow working state, giving SFCLTurn on signal to simultaneously give SL1、SL2Alternately turn on the signal and then turn off BrkFCLAnd LCS, GBCIB-FCL enters a pre-current limiting working state. The current in the current limiter flows through the auxiliary branch, the path of which is shown in fig. 3. The equivalent impedance of GBCIB-FCL is still small in the pre-current limiting working state. LCS ensures BrkFCLSafety on-off, BrkFCLThe commutation may be forced out of service. Meanwhile, the pre-current-limiting working state can improve the speed of the GBCIB-FCL entering the current-limiting working state so as to accelerate the suppression of the subsequent fault current.
The current limiting operating state of GBCIB-FCL is shown in FIG. 4. To give SFCLOff signal, SL1、SL2Keep alternately conducting and trigger TbyA valve block. The current in the current limiter flows through the current limiting branch (through the shunt resistor and the coupling inductor).
The open bypass state of GBCIB-FCL is shown in FIG. 5. At this time BrkFCLBreaking, SFCLOff, SL1、SL2And (6) turning off. Triggered TbyThe valve group puts the bypass branch into the direct current inductance to provide an energy discharge loop, and the current in the GBCIB-FCL mainly flows through the bypass branch.
In the process of establishing a mathematical model of the GBCIB-FCL topological current limiting process, S is assumed to be in the processL1Off, SL2And conducting, neglecting other nonlinear devices in the current limiting part, and taking the relevant reference direction. The mathematical model equivalent circuit of GBCIB-FCL is shown in FIG. 6.
The equivalent circuit column write equation according to fig. 6:
arranging formula (4) into a matrix form:
taking the state variable x ═ iL1 iL2 iL)TThe input U ═ U, lists the equation of state:
wherein:
in the same way, when SL1Conducting SL2Similar results are obtained when switched off.
The main parameter of GBCIB-FCL is selected as a simulation experiment test method, and the parameter needing to be designed comprises inductance L1And L2Mutual inductance k and alternate signal frequency fsw。
Using only the current limiting pair L of GBCIB-FCL of FIG. 11And L2Mutual inductance k and alternate signal frequency fswAnd (5) carrying out analytical design. Taken from the induction of L ═ L1＝L2Fig. 7 shows different cases in which the short-circuit current is limited when the current limiting portion operates alone, by changing from 50mH to 150mH in steps of 25mH and changing the mutual inductance k from 0 to 1 in steps of 0.1. After short circuit occurs for 0.5ms, the current rises rapidly to reach a peak value of 3.62kA, and at the moment, the current limiting part is put into use to realize short circuitThe current is limited. The short-circuit current is limited to a lower level when the self-inductance L increases, but the suppression effect by increasing the self-inductance is not significant as the self-inductance L increases to 100mH or more. When the mutual inductance k is increased, the short-circuit current is also inhibited, and meanwhile, a certain amount of energy is stored due to mutual inductance, the equivalent reactance of the current limiting part is increased, and the current attenuation speed is increased.
Taking the frequency f of the alternate signalswThe resulting fault current waveform is shown in fig. 8 when stepped from 1.5kHz to 3.5kHz at 0.25 kHz. When alternating the signal frequency fswIncreasing, fault current level decreasing at the same time; when f isswWhen the frequency is increased to 2.5kHz or more, the effect of suppressing the fault current is not sufficiently exhibited. Considering the problems of current limiting effect, high-voltage reactance manufacturing cost, insulation safety and the like, the self-inductance L of the coupling inductor is selected to be L1＝L2100mH, coupling coefficient k 0.9, alternating signal frequency fsw＝2500Hz。
The invention designs a coupling inductance type bidirectional direct current limiter with a direct current distribution network grounding bypass function. The topology is composed of a main current flow portion and a current limiting portion. The main current-flowing part is composed of a quick mechanical switch and a load transfer switch which are connected in series. When the system has short-circuit fault, the transfer of short-circuit current is realized by inputting a current-limiting part, and the part consists of an auxiliary branch, a current-limiting branch and a bypass branch. The auxiliary branch circuit is a parallel solid-state switch and is used for matching with the main through-current branch circuit to transfer fault current and matching with the direct-current circuit breaker to carry out reclosing operation after current transfer. In the current-limiting branch circuit, the characteristics of low frequency and high frequency resistance of an inductor and quick and controllable full-control devices are utilized to convert the direct-current fault current into high-frequency alternating current so as to realize the purpose of quick and efficient suppression of the direct-current fault current. The bypass branch is formed by connecting the thyristor valve group and the bypass resistor in series, so that the inductor on the fault side can be bypassed, and fault isolation is realized. The auxiliary branch, the current limiting branch and the bypass branch realize bidirectional power exchange through a diode bridge. On the basis, a mathematical model of the current limiter during current limiting operation is established, and a method for selecting main parameters in the current limiter is provided. The four working states of 'normal-pre-current limiting-disconnection bypass' are provided, and the method is convenient to apply to an actual direct-current power system. The method has the advantages of being scientific and reasonable, strong in applicability, high in reliability and good in effect.
The present invention includes the following aspects:
(1) and designing the topology of the coupled inductance type bidirectional direct current limiter with the grounding bypass function. The main current-flowing part is composed of a quick mechanical switch and a load transfer switch which are connected in series. When the system has short-circuit fault, the transfer of short-circuit current is realized by inputting a current-limiting part, and the part consists of an auxiliary branch, a current-limiting branch and a bypass branch. The auxiliary branch circuit is a parallel solid-state switch and is used for matching with the main through-current branch circuit to transfer fault current and matching with the direct-current circuit breaker to carry out reclosing operation after current transfer. In the current-limiting branch circuit, the characteristics of low frequency and high frequency resistance of an inductor and quick and controllable full-control devices are utilized to convert the direct-current fault current into high-frequency alternating current so as to realize the purpose of quick and efficient suppression of the direct-current fault current. The bypass branch is formed by connecting the thyristor valve group and the bypass resistor in series, so that the inductor on the fault side can be bypassed, and fault isolation is realized. The auxiliary branch, the current limiting branch and the bypass branch realize bidirectional power exchange through a diode bridge.
(2) The four working states of 'normal-pre-current limiting-disconnection bypass' of the current limiter are designed. When the current limiter works normally, the internal current flows through the main current branch circuit, and the current limiting part is bypassed. Because the current does not flow through the switching device, the diode or the resistor, the lower loss in normal work is ensured. The equivalent impedance of the current limiter is still small in the pre-current limiting working state. The mechanical switch may be taken out of service by forcing commutation. Meanwhile, the speed of the current limiter entering the current limiting working state can be increased in the pre-current limiting working state, so that the suppression of subsequent fault current is accelerated. When the current limiter works in a current limiting state, the inductive switch is kept alternately conducted to trigger the bypass thyristor valve group. The current in the current limiter flows through the shunt resistor and the coupling inductor. When the current limiter is in a bypass state, the triggered bypass thyristor valve group puts the bypass branch into an energy leakage loop for the direct current inductor, and the fault isolation time is accelerated.
(3) A mathematical model of the current limiting process is established. In the modeling process, other nonlinear devices in the current limiting part are ignored, and the associated reference direction of the devices is taken, so that the mathematical model with the grounding bypass function under the current limiting state of the coupled inductive bidirectional direct current limiter is obtained. The mathematical model may provide a reference for theoretical analysis of the flow restrictor.
(4) A method of selecting the principal parameters within the flow restrictor is given. The self inductance of the coupling inductance type bidirectional direct current limiter with the grounding bypass function, the mutual inductance of the coupling inductance and the switching frequency are subjected to parameter setting through a simulation test method. The parameter selection may provide a reference for the manufacture of the flow restrictor.
Claims (1)
1. The utility model provides a two-way direct current limiter of coupling inductance formula of direct current distribution network ground connection bypass function which characterized in that: the method comprises the following steps:
s1 designing topology of GBCIB-FCL
GBCIB-FCL is composed of main current part and current limiter, the main current part is composed of fast mechanical switch BrkFCLAnd load transfer switch connected in series, when short circuit fault occurs in the system, the short circuit current transfer is realized by switching in current-limiting part, which comprises auxiliary branch, current-limiting branch and bypass branch, the auxiliary branch is parallel IGBT solid switch SFCLThe current-limiting branch circuit utilizes the characteristics of low frequency of passing inductance, high frequency of resistance and quick controllability of full control devices to convert direct current fault current into high-frequency alternating current, and the bypass branch circuit is a thyristor valve group TbyAnd a shunt resistor RbyThe auxiliary branch, the current limiting branch and the bypass branch realize the bidirectional power exchange of GBCIB-FCL through a diode bridge;
s2 designing four working states of normal-pre-limiting flow-disconnecting bypass of GBCIB-FCL topology
(1) When the DC line is in normal operation, BrkFCLAnd LCS closed conduction, SFCLOff, SL1、SL2Turning off;
(2) when GBCIB-FCL is in the pre-restricted flow working state, giving SFCLTurn on signal to simultaneously give SL1、SL2Alternately turn on the signal and then turn off BrkFCLLCS, GBCIB-FCL enters into the pre-current-limiting working state, and the current in the current limiter flows through the auxiliary branch;
(3) to give SFCLOff signal, SL1、SL2Keep alternately conducting and trigger TbyThe current in the current limiter flows through the current limiting branch circuit, the shunt resistor and the coupling inductor;
(4)BrkFCLbreaking, SFCLOff, SL1、SL2Off, triggered TbyThe valve group puts the bypass branch into a direct current inductor to provide an energy leakage loop, and the current in the GBCIB-FCL mainly flows through the bypass branch;
s3, establishing model of GBCIB-FCL topology current limiting process
Suppose that S is nowL1Off, SL2Conducting, neglecting other nonlinear devices in the current limiting part, taking a relevant reference direction, and obtaining an equivalent circuit:
arranging formula (1) into a matrix form:
taking the state variable x ═ iL1 iL2 iL)TThe input U ═ U, lists the equation of state:
wherein:
in the same way, when SL1Conducting SL2Similar results can be obtained when switching off;
s4 method for selecting main parameters of GBCIB-FCL
The parameters to be designed include inductance L1And L2Mutual inductance k and crossFrequency f of the signalswTaken from the induction of L ═ L1＝L2Changing from 50mH to 150mH in steps at 25mH, and changing the mutual inductance k from 0 to 1 in steps at 0.1 interval to obtain the condition that the short-circuit current is limited when the current limiting part works alone, and taking the frequency f of the alternate signalswThe resulting fault current waveform was stepped from 1.5kHz to 3.5kHz at 0.25 kHz.
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| CN111740395A (en) * | 2020-05-21 | 2020-10-02 | 东北电力大学 | Topological structure of inductive coupling type high-voltage direct-current limiting circuit breaker |
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| CN111740395A (en) * | 2020-05-21 | 2020-10-02 | 东北电力大学 | Topological structure of inductive coupling type high-voltage direct-current limiting circuit breaker |
Non-Patent Citations (1)
| Title |
|---|
| 王振浩 等: "耦合电感式双向直流限流器及其与直流断路器的联合运行策略", 《中国电机工程学报》 * |
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Application publication date: 20220415 |