CN214227826U - Resistance-inductance type direct current fault current limiter based on pre-charging commutation capacitor - Google Patents

Resistance-inductance type direct current fault current limiter based on pre-charging commutation capacitor Download PDF

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CN214227826U
CN214227826U CN202120216996.5U CN202120216996U CN214227826U CN 214227826 U CN214227826 U CN 214227826U CN 202120216996 U CN202120216996 U CN 202120216996U CN 214227826 U CN214227826 U CN 214227826U
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thyristor
current
branch
resistor
capacitor
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张孝荟
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Guizhou University
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Guizhou University
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Abstract

The utility model discloses a hinder and feel type direct current fault current limiter based on precharge commutation electric capacity, this current limiter comprises 5 branch roads: the branch circuit 1 is an auxiliary current limiting branch circuit and consists of a first thyristor and a first resistor; the branch 2 is a main current-limiting branch and consists of a second thyristor, a second resistor and a reactor; the branch 3 is a low-loss circulation branch and consists of a third thyristor and a diode connected in reverse parallel with the third thyristor; the branch 4 and the branch 5 together form a pre-charging loop, wherein the branch 4 is a branch where the phase-change capacitor is located, and the branch 5 is composed of a fourth thyristor, a third resistor and a second capacitor. The method is suitable for high-power high-voltage direct-current transmission.

Description

Resistance-inductance type direct current fault current limiter based on pre-charging commutation capacitor
Technical Field
The utility model belongs to the technical field of electric power system, concretely relates to hinder inductance type direct current fault current limiter based on precharge commutation electric capacity.
Background
The flexible direct-current power grid can realize smooth access of distributed new energy and decoupling control of active power reactive power, can transmit power in a long distance, is low in power transmission loss, does not have the problems of reactive power compensation, commutation failure and the like, and is considered as a key technology for constructing the future global energy Internet. However, the dc power grid has the characteristics of "low inertia and low impedance", and after a short-circuit fault occurs on the dc side, the dc capacitor is rapidly discharged, the dc current rapidly rises, and a large fault impact current easily causes the converter device to be damaged due to overcurrent. The fast breaking of a fault line based on a high voltage direct current breaker is one of the protection schemes currently suitable for handling direct current faults in a direct current power grid. In order to reduce the rising rate of fault current, reduce the current stress borne by the direct current circuit breaker during the breaking and reduce the cost of the direct current circuit breaker, the direct current fault current limiter suitable for the direct current power grid is researched, and the direct current fault current limiter has obvious significance.
Current dc Fault Current Limiters (FCLs) can be divided into 3 classes: superconducting current limiters, solid state current limiters, and hybrid current limiters. The superconducting current limiter has high manufacturing cost, so that the economic performance of a power grid cannot be guaranteed, and the high-voltage superconducting current limiter can bring a new problem of uniform quench; the solid-state current limiter is limited by the capability of a single power electronic device, and a large number of devices are often required to be connected in series and in parallel to meet high-voltage and high-current requirements, so that the on-state loss caused by the high-voltage and high-current requirements can reduce the economy; hybrid current limiters are currently mainly focused on medium and low pressure systems. Therefore, it is significant to design a fault current limiter suitable for a high-voltage direct-current power grid.
SUMMERY OF THE UTILITY MODEL
An object of the utility model is to provide a hinder and feel type direct current fault current limiter based on precharge commutation electric capacity is applicable to high-power high voltage direct current transmission.
The technical scheme for realizing the purpose is as follows:
a pre-charging commutation capacitor-based resistance-inductance type direct current fault current limiter comprises: a first thyristor, a second thyristor, a third thyristor, a fourth thyristor, a first resistor, a second resistor, a third resistor, a reactor, a commutation capacitor, a second capacitor and a diode,
the anode of the first thyristor is connected with the input end, and the cathode of the first thyristor is connected with the first end of the first resistor;
the anode of the third thyristor is connected with the input end, and the cathode of the third thyristor is connected with the output end;
the cathode of the diode is connected with the input end, and the anode of the diode is connected with the output end;
one end of the phase-change capacitor is connected with the output end, and the other end of the phase-change capacitor is connected with the second end of the first resistor;
the anode of the second thyristor is connected with the second end of the first resistor, and the cathode of the second thyristor is connected with the first end of the reactance through the second resistor; the second end of the reactance is connected with the output end;
the anode of the fourth thyristor is connected with the second end of the first resistor, and the cathode of the fourth thyristor is connected with the first end of the second capacitor through the third resistor; and the second end of the second capacitor is grounded.
Preferably, the input end is externally connected with a converter station; the output end is connected with a direct current bus.
Preferably, the converter station is a rectifier station or an inverter station.
The utility model has the advantages that: the utility model discloses an effectual design, steady state loss is low, is applicable to high-power high voltage direct current transmission. Compared with an IGBT (insulated gate bipolar transistor), the thyristor has the same through-current capacity, is lower in manufacturing difficulty and effectively saves cost. The current limiting resistor and the current limiting reactance are adopted for comprehensive current limiting, so that the fault current rise rate can be restrained, and the fault current amplitude can be limited. Meanwhile, the investment cost of the circuit breaker can be effectively saved.
Drawings
Fig. 1 is a schematic diagram of a topology of a resistance-inductance type dc fault current limiter according to the present invention;
FIG. 2 is a schematic diagram of a current limiting circuit model according to the present invention;
fig. 3 is a schematic diagram of the current flow when the system of the present invention is powered on;
FIG. 4 shows the structure of the present invention0—t1Phase current flow schematic;
FIG. 5 shows the structure of the present invention1—t2Phase current flow schematic;
FIG. 6 shows the structure of the present invention2—t3Phase current flow schematic;
FIG. 7 shows a view of the present invention3After the moment the current flows to the diagram.
Detailed Description
The present invention will be further explained with reference to the accompanying drawings.
Referring to fig. 1, the present invention provides a resistance-sensing dc fault current limiter based on a pre-charging commutation capacitor, including: first thyristor T1A second thyristor T2A third thyristor T3The fourth thyristor TcA first resistor R1A second resistor R2A third resistor RcReactance L2And a phase-change capacitor C1A second capacitor C2And a diode D3。
First thyristor T1Anode of the first resistor is connected with the input end A, and cathode of the first resistor is connected with the first resistor R1The first end of (a). Third thyristor T3The anode of the anode is connected with the input end A, and the cathode is connected with the output end B. Diode D3The cathode of the anode is connected with the input end A, and the anode is connected with the output end B. Phase-change capacitor C1One end of the first resistor is connected with the output end B, and the other end of the first resistor is connected with the first resistor R1The second end of (a). Second thyristor T2Anode of (2) is connected with a first resistor R1The cathode passes through a second resistor R2Connecting reactance L2A first end of (a); reactance L2The second end of the first switch is connected with the output end. Fourth thyristor TcAnode of (2) is connected with a first resistor R1A cathode is connected with a third electrode R3Resistance-connected second capacitor C2A first end of (a); second capacitor C2The second terminal of (a) is grounded.
The current limiter is connected in series between the converter station and the direct current bus, namely: the input end A is externally connected with a converter station; the converter station is a rectifying station or an inverting station. The output end B is connected with a direct current bus. When the input terminal A is connected with the rectifier station, the load current flows through the third thyristor T3. When the input end A is connected with the inverter station, the load current flows through the diode D3. When a short-circuit fault occurs on the direct current side, the fault current always points to B from A; therefore, the subsequent operation process of the fault current limiter is completely the same whether the converter station connected with the input end a of the fault current limiter is a rectifier station or an inverter station.
As shown in figure 1, the utility model is composed of 5 branches. Branch 1 is an auxiliary current-limiting branch and is composed of a first thyristor T1And a first resistor R1Forming; branch 2 is the main current limiting branch and is composed of a second thyristor T2A second resistor R2And a reactance L2(ii) a Branch 3 is a low loss current branch formed by a third thyristor T3And a diode D connected in inverse parallel therewith3Composition is carried out; branch 4 is a commutation capacitor (also called first capacitor) C1The branch is located; fourth thyristor T in branch 5cFor pre-charging branch switches, third resistors RcFor the purpose of controlling the charging time and preventing overcurrent in the current-limiting resistor in the pre-charging branch, branches 4 and 5 together form the pre-charging branch. Adjusting capacitor phase-changing capacitor C1And a second capacitor C2Ratio to realize the phase-change capacitance C1Setting of the pre-charge voltage while ensuring the anti-parallel connection of the second thyristor T2And is not reverse breakdown.
A second resistor R2The main current limiting resistor is connected in series into a fault loop to limit fault current after short circuit fault occurs; a first resistor R1Is an auxiliary current limiting resistor for limiting the phase change capacitor C1Current during discharge, thereby protecting diode D3And a first thyristor T1On the other hand in the third thyristor T3Second resistor R in main current-limiting branch circuit after being switched off2And a reactance L2Together suppressing the fault current. In the phase-change capacitor C1A second capacitor C2After full charge, the current flows to the load, the current in the pre-charging branch is zero, and the fourth thyristor TcOff, thereafter Tc-Rc-C2Cut off from the loop and do not participate in the current limiting process. The currents flowing in the branches 1-3 are designated i respectively1-i3A phase-change capacitor C1The branch current is named as ic。
As shown in fig. 2, in a normal state, after the system is powered on, the current supplies power to the load through the low-loss circulation branch, and then the system monitors the loop current all the time. After the fault, the system detects that the loop current is greater than the set value and immediately gives the first thyristor T1A trigger pulse is sent in and simultaneously a second thyristor T is also sent2Sending a continuous trigger signal; first thyristor T1Because the capacitor C always bears the phase change1Is conducted by the forward voltage of the capacitor C1Starting to discharge, the discharge current causing the third thyristor T3Turning off; then the fault current gives a capacitor phase-changing capacitor C1Charging in view of the second thyristor T2When the trigger signal is applied, it is immediately turned on when it starts to bear the forward voltage, and both current-limiting branches 1 and 2 are put into the fault loop to suppress the fault current. Cs、Ls、RsRespectively the system equivalent capacitance, reactance and resistance at the converter station side.
As shown in fig. 3: to the third thyristor T3The fourth thyristor TcSending trigger pulse to make it conductive, the current flows through the third thyristor T3Then, part of the current flows to the pre-charging branch circuit to supply the phase-changing capacitor C1A second capacitor C2Charging; the other part supplies power to the load through a power transmission line. After the charging is finished, the current flows to the load completely, the current of the pre-charging branch is zero, and the fourth thyristor TcAnd (6) turning off. Then Tc-Rc-C2Cut off from the loop and do not participate in the current limiting process.
The operation of the current limiter circuit is analyzed as follows:
before a fault (time) occurs, the system supplies power to the load via a low-loss branch, t0When a short-circuit fault occurs at a moment, the current limiter acts as follows:
1)t0—t1time of day
At t0After a fault at that moment, the current increases rapidly, t0—t1During this time period, the short circuit current flows through the low loss branch to the fault, as shown by the dashed line in loop 1 in fig. 4.
According to KVL law, formula (1) can be obtained, and the solution is shown as formula (2):
Figure BDA0002916761820000041
assume that the initial condition at the moment of failure is
Figure BDA0002916761820000042
idc(t0)＝I0Then, the expressions of the capacitor voltage and the fault current can be obtained:
Figure BDA0002916761820000043
wherein:
Figure BDA0002916761820000051
in the process
Figure BDA0002916761820000052
The system is an under-damping condition of an RLC second-order dynamic circuit and is an oscillation attenuation discharging process.
t1The time system detects the loop current idcGreater than a set value IsetImmediately feeding T to the thyristor1Sending in a trigger pulse, T1Due to bearing C all the time1Is conducted by the forward voltage of the capacitor C1Immediate discharge, with the discharge current shown as loop 2 dashed line in fig. 4; phase-change capacitor C1Must be greater than the fault current to be able to discharge at t2The third thyristor T is turned off successfully at all times3. Setting the initial voltage of the commutation capacitor to Uc1The condition that the commutation process is successful is that the commutation capacitor voltage and the branch current satisfy the condition shown in the formula (5):
Figure BDA0002916761820000053
2)t1—t2time of day
t1At the moment, the third thyristor T3Is turned off, after which the circuit goes to CsAnd C1In series through Ls、RsAnd R1During discharging, fault current is constantly supplied to change phaseCapacitor C1Charging in the reverse direction until
Figure BDA0002916761820000055
As shown in fig. 5, t1—t2The process is a three-order dynamic circuit solving process, and a formula (5) can be listed according to circuit principle knowledge:
Figure BDA0002916761820000054
3)t2—t3time of day
To t2At the moment, the voltage u of the commutation capacitorc1When the fault current is equal to 0, the fault current is continuously supplied to the commutation capacitor C1Reverse charging, T2And immediately conducts as a result of beginning to bear the forward voltage. As shown in fig. 6, t2—t3The process is a four-order dynamic circuit solving process, and a formula (6) can be listed according to circuit principle knowledge:
Figure BDA0002916761820000061
3)t3after the moment of time
t3Time of day, commutation capacitor C1When the current is fully charged, the current of the branch is zero, the fault current flows into the current-limiting branch 2, and the capacitor C1No longer has an effect. From this point, both current limiting branches 1 and 2 are put into the fault loop to suppress the fault current, and the action process of the current limiter is completed, as shown in fig. 7. At this time, the circuit returns to the second-order circuit discharging process, which is related to t0—t1The difference of the discharging process is that the system resistance and the reactance are increased through the input process of the current limiter, so that the time constant of the second-order circuit is changed, and the fault current is restrained from further increasing.
The above embodiments are provided only for the purpose of illustration, not for the limitation of the present invention, and those skilled in the relevant art can make various changes or modifications without departing from the spirit and scope of the present invention, therefore, all equivalent technical solutions should also belong to the scope of the present invention, and should be defined by the claims.

Claims (3)

1. A resistance-inductance type direct current fault current limiter based on a pre-charging commutation capacitor is characterized by comprising: a first thyristor, a second thyristor, a third thyristor, a fourth thyristor, a first resistor, a second resistor, a third resistor, a reactor, a commutation capacitor, a second capacitor and a diode,
the anode of the first thyristor is connected with the input end, and the cathode of the first thyristor is connected with the first end of the first resistor;
the anode of the third thyristor is connected with the input end, and the cathode of the third thyristor is connected with the output end;
the cathode of the diode is connected with the input end, and the anode of the diode is connected with the output end;
one end of the phase-change capacitor is connected with the output end, and the other end of the phase-change capacitor is connected with the second end of the first resistor;
the anode of the second thyristor is connected with the second end of the first resistor, and the cathode of the second thyristor is connected with the first end of the reactance through the second resistor; the second end of the reactance is connected with the output end;
the anode of the fourth thyristor is connected with the second end of the first resistor, and the cathode of the fourth thyristor is connected with the first end of the second capacitor through the third resistor; and the second end of the second capacitor is grounded.
2. The resistive-inductive direct-current fault current limiter based on the pre-charging commutation capacitor as claimed in claim 1, wherein the input end is externally connected with a converter station; the output end is connected with a direct current bus.
3. A pre-charging commutation capacitor-based resistive-inductive type direct current fault current limiter according to claim 2, wherein the converter station is a rectifier station or an inverter station.
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