CN109921390B - Voltage characteristic-based short-circuit current absorption branch exit control method and device - Google Patents
Voltage characteristic-based short-circuit current absorption branch exit control method and device Download PDFInfo
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Abstract
The invention provides a method and a device for controlling exit of a short-circuit current absorption branch circuit based on voltage response characteristics. According to the method, when the voltage characteristic value of the monitored alternating current bus is detected to be higher than a preset voltage threshold value, a short-circuit current absorption branch exit instruction is generated; and responding to the short-circuit current consumption branch exit instruction, and controlling the short-circuit current consumption branch to exit from the power grid. The method provided by the invention can timely withdraw the short-circuit current absorption branch circuit from the power system after the short-circuit fault in the power system is isolated, so that the system is recovered to a normal state as soon as possible.
Description
Technical Field
The invention belongs to the field of safety and stability control of power systems, and relates to a method and a device for controlling exit of a short-circuit current absorption branch circuit based on voltage response characteristics.
Background
With the continuous expansion of the scale of the power grid in China, the net racks are more and more dense, and the short-circuit current level of the system also rises rapidly. If the short-circuit current exceeds the breaking capacity of the protection switch, the protection switch cannot break the short-circuit current, and the fault cannot be isolated, so that serious accidents such as line and equipment burnout, system stability damage and the like are further caused. Therefore, effective measures must be taken to actually reduce the short-circuit current level.
The current common means comprise grid structure optimization, line pulling and stopping, fault current limiter installation and the like. These methods may affect system safety, or have low reliability, high false alarm rate, and poor current limiting effect.
Disclosure of Invention
The invention provides a method and a device for controlling exit of a short-circuit current absorption branch circuit based on voltage response characteristics, and aims to solve the problem that fault measures taken when the short-circuit current is too large cannot exit in time at present.
In a first aspect, the present invention provides a method for controlling exit of a short-circuit current absorption branch based on voltage response, including:
when the voltage characteristic value of the monitored alternating current bus is detected to be higher than a preset voltage threshold value, generating a short-circuit current absorption branch exit instruction;
the short-circuit current absorption branch circuit is a shunt branch circuit which is connected with a bus in parallel and can be controllably put into or taken out of the power grid;
and responding to the short-circuit current consumption branch exit instruction, and controlling the short-circuit current consumption branch to exit from the power grid.
In particular, the exit control method described herein,
the detecting that the monitored voltage characteristic value of the alternating-current bus is higher than a preset voltage threshold value comprises the following steps:
and in M continuous detection periods, detecting that the voltage characteristic value of the monitored alternating-current bus is higher than a preset voltage threshold value, wherein M is a positive integer.
In particular, the exit control method described herein,
the detecting that the monitored voltage characteristic value of the alternating-current bus is higher than a preset voltage threshold value comprises the following steps:
in M continuous detection periods, the detection period number M1 meeting the condition that the voltage characteristic value is higher than the preset voltage threshold value is larger than the detection period number M2 meeting the condition that the voltage characteristic value is not higher than the preset voltage threshold value, M is a positive integer, M1 is a positive integer, and M2 is a positive integer.
Specifically, the exiting control method, where it is detected that the monitored voltage characteristic value of the ac bus is lower than a preset voltage threshold value, includes:
in continuous M detection periods, the characteristic value of the bus voltage is lower than a preset voltage threshold value;
and in the following continuous N detection periods, the bus voltage characteristic value is higher than a preset voltage threshold value, wherein M is not more than N, M is a positive integer, and N is a positive integer.
Specifically, the exit control method further includes:
and generating a short-circuit current absorption branch exit instruction when the on-off state of any fault protection switch in all the branches connected in parallel with the bus voltage is off and when the voltage characteristic value of the monitored alternating current bus is detected to be higher than a preset voltage threshold value.
In particular, the exit control method described herein,
the short-circuit current absorption branch comprises a bidirectional thyristor which is controllably connected with or disconnected from the bus;
and the reactor is connected with the bidirectional thyristor in series and is grounded.
In a second aspect, the present invention provides a short-circuit current control device based on voltage response, comprising:
the voltage characteristic value acquisition element is used for detecting the voltage characteristic value of the monitored alternating current bus;
and the control element is used for generating a short-circuit current absorption branch exit instruction when detecting that the monitored voltage characteristic value of the alternating current bus is higher than a preset voltage threshold value.
Specifically, the control device further includes:
the instruction driving element is used for receiving the short-circuit current absorption branch exit instruction and sending the short-circuit current absorption branch exit instruction to the short-circuit current absorption branch so that the short-circuit current absorption branch exits from the power grid in response to the short-circuit current absorption branch exit instruction;
the short-circuit current absorption branch circuit is a shunt branch circuit which is connected with the bus in parallel and can be controllably switched into or switched out of the power grid.
Specifically, the control device further includes:
the protection switch state acquisition element is used for receiving and processing a switching-off signal of the protection switch;
the control element is further used for generating a short-circuit current absorbing branch exit instruction when the on-off state of any fault protection switch in all the branches connected in parallel with the bus voltage is off and when the monitored voltage characteristic value of the alternating current bus is detected to be higher than a preset voltage threshold value.
Specifically, the control device further includes:
the short-circuit current absorption branch comprises a bidirectional thyristor which is controllably connected with or disconnected from the bus;
and the reactor is connected with the bidirectional thyristor in series and is grounded.
According to the short-circuit current absorption branch exit control method and device based on voltage response, the short-circuit current absorption branch exit instruction is generated based on the level change of the bus voltage before and after the fault, the short-circuit current absorption branch can be timely exited from the power system after the short-circuit fault in the power system is isolated, and the system is enabled to be restored to the normal state as soon as possible.
Drawings
A more complete understanding of exemplary embodiments of the present invention may be had by reference to the following drawings in which:
FIG. 1 is a schematic flow chart of a method for exiting a short-circuit current absorption branch based on voltage response according to a preferred embodiment of the present invention;
FIG. 2 is a schematic diagram of the short-circuit current control device based on voltage response according to the preferred embodiment of the present invention;
FIG. 3 is a schematic flow chart diagram of a short-circuit current absorption branch exit method based on voltage response according to another embodiment;
fig. 4 is a waveform plot of bus voltage before and after short circuit fault isolation in a preferred embodiment of the present invention.
Detailed Description
Example embodiments of the present invention will now be described with reference to the accompanying drawings, however, the invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein, which are provided for a complete and complete disclosure of the invention and to fully convey the scope of the invention to those skilled in the art. The terminology used in the exemplary embodiments illustrated in the accompanying drawings is not intended to be limiting of the invention. In the drawings, the same units/elements are denoted by the same reference numerals.
Unless otherwise defined, terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Further, it will be understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense.
At present, the phenomenon that the short-circuit current level of a secondary voltage power grid exceeds the standard is common. When a short-circuit fault occurs in any branch on an ac bus of a station such as the substation shown in fig. 2, a measure for limiting a short-circuit current needs to be taken in time to ensure that a fault protection switch is reliably turned off and the fault is isolated in time. After fault isolation, the measures for limiting the short-circuit current need to be quitted in time, so that the system is restored to a normal state as soon as possible.
It should be understood that, in the event of a short-circuit fault in a branch, the fault protection switch K remains closed when a short-circuit current greater than the maximum short-circuit current that can be switched off flows, but continuously detects the short-circuit current in real time; the fault protection switch is switched off until the short-circuit current flowing through the fault protection switch is reduced to be not more than the maximum short-circuit current which can be switched off; and after the fault is eliminated, the fault protection switch is closed and waits for the response to the next fault.
Specifically, the protection switch comprises a body and an operation element, the operation element controls local switch opening or closing, generates an overcurrent state signal or an on-off state signal, and provides the overcurrent state signal or the on-off state signal for other power system devices to perform state monitoring or logic judgment. As shown in fig. 2, the short-circuit current absorbing branch is installed on a bus of a station (e.g., a substation) to be detected. The short-circuit current accommodating branch comprises a power electronic switching device 10 which is controllably connected with or disconnected from the bus bar, and a reactor 20 connected with the power electronic switching device in series, wherein the reactor 20 is reliably grounded.
The short-circuit current absorbing branch is equivalent to a parallel shunt branch which can be controllably connected to the bus when the short-circuit fault occurs in the power grid. Specifically, before the short-circuit fault occurs in the power grid, the short-circuit current absorbing branch is withdrawn from the power grid, or the current value obtained from the bus is approximately zero.
After the short-circuit fault occurs in the power grid, the short-circuit current absorption branch circuit is controlled to be put into the power grid, and a first larger current value is obtained from the bus before a protection switch of the short-circuit branch circuit is not switched off; and after the protection switch of the short-circuit branch is switched off, obtaining a larger second current value from the bus, wherein the second current value is larger than the first current value.
After the protective switch of the short-circuit branch is reliably opened, the short-circuit fault is isolated. In this case, the short-circuit current-absorbing branch needs to be controllably withdrawn from the grid, or the current value taken from the bus bar is approximately zero.
According to the short-circuit current absorption branch exit control method and the short-circuit current control device based on voltage response, the short-circuit current absorption branch exit instruction is generated based on the horizontal change of the bus voltage before and after the fault, the short-circuit current absorption branch can be timely exited from the power system after the short-circuit fault in the power system is isolated, and the system is ensured to be timely recovered to a normal state.
Specifically, when the short-circuit current absorption branch is controlled to be disconnected with the bus, the probability of early disconnection needs to be minimized; and the probability of delayed disconnection is minimized.
As shown in fig. 1, the method for controlling the exit of the short-circuit current absorption branch based on voltage response in the preferred embodiment of the present invention includes:
step S100: when the voltage characteristic value of the monitored alternating current bus is detected to be higher than a preset voltage threshold value, a short-circuit current absorption branch exit instruction is generated;
the short-circuit current absorption branch circuit is a shunt branch circuit which is connected with a bus in parallel and can be controllably put into or taken out of the power grid;
step S200: and responding to the short-circuit current consumption branch exit instruction, and controlling the short-circuit current consumption branch to exit from the power grid.
It should be understood that the detection may include one detection period, or may include a plurality of consecutive detection periods. The detection period can be an update period of the voltage and the current of each measurement and control element in the intelligent substation, or a sampling period of the voltage signal acquired by the voltage characteristic value acquisition element; and may also include time consuming transmissions over the communication link.
In particular, the exit control method described herein,
the detecting that the monitored voltage characteristic value of the alternating-current bus is higher than a preset voltage threshold value comprises the following steps:
in M continuous detection periods, detecting that the voltage characteristic value of the monitored alternating current bus is higher than a preset voltage threshold value, wherein M is a positive integer.
In order to avoid misoperation caused by random peak values and other interference quantities in voltage amplitude measurement, in the method, when the voltage characteristic value of the alternating current bus detected in continuous M detection periods is higher than a preset voltage threshold value, the voltage is considered to have risen to a reasonable level, short-circuit faults are isolated, fault measures need to be withdrawn, and the system is ensured to be timely recovered to a normal state.
The method has the advantages of more introduced information quantity and more comprehensive criteria, thus having good reliability and low false alarm rate.
In particular, the exit control method described herein,
the detecting that the monitored voltage characteristic value of the alternating-current bus is higher than a preset voltage threshold value comprises the following steps:
in M continuous detection periods, the detection period number M1 meeting the condition that the voltage characteristic value is higher than the preset voltage threshold value is larger than the detection period number M2 meeting the condition that the voltage characteristic value is not higher than the preset voltage threshold value, wherein M is a positive integer, M1 is a positive integer, and M2 is a positive integer.
In order to avoid peak-to-valley fluctuation in the voltage amplitude measurement, in the method, when the detection period number M1 meeting the condition that the voltage characteristic value is higher than the preset voltage threshold value is greater than the detection period number M2 meeting the condition that the voltage characteristic value is not higher than the preset voltage threshold value, the voltage is considered to have risen back to a reasonable level, the short-circuit fault is isolated, and the fault measures need to be quitted to ensure that the system is timely restored to a normal state.
The method has the advantages of more introduced information quantity and more comprehensive criteria, thus having good reliability and low false alarm rate.
Specifically, the exiting control method, detecting that the characteristic voltage value of the monitored alternating-current bus is lower than a preset voltage threshold value, includes:
in M continuous detection periods, the characteristic value of the bus voltage is lower than a preset voltage threshold value;
and in the following continuous N detection periods, the bus voltage characteristic value is higher than a preset voltage threshold value, wherein M is not more than N, M is a positive integer, and N is a positive integer.
In order to avoid the risk of judgment based on absolute values, in the method, the bus voltage characteristic value is lower than a preset voltage threshold value in continuous M detection periods; and in the following continuous N detection periods, when the bus voltage characteristic value is higher than a preset voltage threshold, the voltage is considered to be increased back to a reasonable level from the short-circuit fault state, the short-circuit fault is isolated, the fault measures need to be quitted, and the system is ensured to be timely recovered to a normal state.
The method has the advantages of more introduced information quantity and more comprehensive criteria, thus having good reliability and low false alarm rate.
Specifically, the exit control method further includes:
and generating a short-circuit current absorption branch exit instruction when the on-off state of any fault protection switch in all the branches connected in parallel with the bus voltage is off and when the voltage characteristic value of the monitored alternating current bus is detected to be higher than a preset voltage threshold value.
The method is based on the fact that after short-circuit fault isolation, the switch on the branch is necessarily in the off state, the off state of the protection on-off is combined with the voltage rising criterion, the fault measures are guaranteed to be quitted after the short-circuit fault is isolated, and the system is guaranteed to be restored to the normal state in time.
The method has the advantages of more introduced information quantity and more comprehensive criteria, thus having good reliability and low false alarm rate.
Specifically, the exit control method is provided,
the short-circuit current absorption branch circuit comprises a bidirectional thyristor which is controllably connected with or disconnected from the bus;
and the reactor is connected with the bidirectional thyristor in series and is grounded.
As shown in fig. 2, the short-circuit current control device based on voltage response according to the preferred embodiment of the present invention includes:
the voltage characteristic value acquisition element is used for detecting the voltage characteristic value of the monitored alternating current bus;
and the control element is used for generating a short-circuit current absorption branch exit instruction when detecting that the monitored voltage characteristic value of the alternating current bus is higher than a preset voltage threshold value.
Specifically, the control device further includes:
the instruction driving element is used for receiving the short-circuit current absorption branch exit instruction and sending the short-circuit current absorption branch exit instruction to the short-circuit current absorption branch so that the short-circuit current absorption branch exits from the power grid in response to the short-circuit current absorption branch exit instruction;
the short-circuit current absorption branch circuit is a shunt branch circuit which is connected with the bus in parallel and can be controllably switched into or switched out of the power grid.
Specifically, the control device further includes:
the protection switch state acquisition element is used for receiving and processing the on-off signal of the protection switch;
the control element is further used for generating a short-circuit current absorbing branch exit instruction when the on-off state of any fault protection switch in all the branches connected in parallel with the bus voltage is off and when the monitored voltage characteristic value of the alternating current bus is detected to be higher than a preset voltage threshold value.
Specifically, the control device further includes:
the short-circuit current absorption branch comprises a bidirectional thyristor which is controllably connected with or disconnected from the bus;
and the reactor is connected with the bidirectional thyristor in series and is grounded.
The short-circuit current control device of the preferred embodiment of the invention controls the short-circuit current absorbing branch to be separated from the bus (including the situation that the current value obtained from the bus is approximate to zero), so that the short-circuit current absorbing branch can be withdrawn from the power system in time after the short-circuit fault in the power system is isolated, the measure amount during the short-circuit fault is reduced, and the safe and stable operation of the power grid is ensured.
It should be understood that the short-circuit current-accommodating branch shown in fig. 2 is equivalent to a reactor that is controllably connected to or disconnected from the bus bar. Various power electronic switching devices are used for controlling the reactor to be connected to or disconnected from the bus, and various electrical connection modes of the power electronic switching devices and the reactor are well known by persons skilled in the art and are not described herein again.
Usually, the short-circuit current absorbing branch and the corresponding short-circuit current control device are deployed with a single station as a minimum unit. In this case, the element characteristics and parameters of the short-circuit current absorption branch, the parameters of the short-circuit current control device and the control logic are adapted to the individual plant.
In particular, a current sensing device may be provided to obtain quantitatively or qualitatively information about the current taken from the bus by the short-circuit current absorption branch.
Preferably, the power electronic switching device is a triac. As a power electronic device that can operate high power currents or voltages, a triac can also provide a status signal indicative of the access current level and/or an on-off status signal indicative of conduction (i.e., closed) or blocking (i.e., open) in real time. After parameter adaptation with a target loop or a power system, the bidirectional thyristor correspondingly has a rated current I 1 And an overcurrent I 2 . After the bidirectional thyristor is closed, the working current is lower than the overcurrent current I 2 When the bidirectional thyristor is in the overcurrent state, the signal is 0 (indicating no overcurrent). After the bidirectional thyristor is closed, the working current is higher than the overcurrent current I 2 When the bidirectional thyristor is in the overcurrent state, the signal is 1 (indicating overcurrent).
As shown in fig. 2, the short-circuit current control device according to the preferred embodiment of the present invention can cover all the branches and their protection switches at the outlet of one station bus.
Before and after a short-circuit fault and fault isolation occur on any branch in the station, in the first stage of closing a protection switch and closing a bidirectional thyristor (at the moment, the short-circuit current absorption branch is put into a power grid), the value of the working current accessed by the bidirectional thyristor is lower than the rated current I 1 (ii) a In the second stage of the disconnection of the protective switch and the closing of the bidirectional thyristor (at this time, the short-circuit current absorption branch is put into the power grid), the working current connected into the bidirectional thyristor is higher than the overcurrent current I 2 (ii) a In the third phase of the disconnection of the protection switch and of the triac (in which case the short-circuit current absorption branch exits from the network), the value of the operating current switched in by the triac is much lower than the nominal current I 1 。
As shown in fig. 4, before and after a short-circuit fault and fault isolation occur in any branch in the plant station, the bus voltage level continuously decreases at the stage when the protection switch is closed, the bidirectional thyristor is disconnected, and the protection switch is in an overcurrent state (at this time, the short-circuit current absorbing branch is not put into the power grid); when the protection switch is closed, the bidirectional thyristor is closed, and the overcurrent state of the protection switch is overcurrent (at the moment, the short-circuit current absorption branch is put into a power grid), the voltage level of the bus is gradually reduced; when the protection switch is disconnected and the bidirectional thyristor is closed (at the moment, the short-circuit current absorption branch is put into the power grid), the voltage level of the bus continuously rises; during the phase of the disconnection of the protection switch and the disconnection of the bidirectional thyristor (at this time, the short-circuit current absorbing branch exits from the power grid), the bus voltage level is kept in a normal operation state.
When the short-circuit current absorption branch circuit is controlled to be separated from the power system, the short-circuit fault measures are required to be ensured not to be switched in error and not to be switched in advance. The probability of early exit is minimized; the probability of a delayed exit is also minimized. At this time, the disconnection of the fault protection switch is a key condition for ensuring that the switch is not switched in advance; and the key condition of not delaying the switching is that the bus voltage is recovered to some extent.
According to the method provided by the embodiment of the invention, after the fault protection switch of the fault branch circuit is reliably disconnected and the bus voltage falls back to a reasonable level, the short-circuit current absorption branch circuit is controlled to be disconnected with the bus.
The following are the definitions of terms and symbols:
protection switch status signal:
boolean variable, 1 for closed, 0 for open
Overcurrent signals of the protection switch:
boolean variables, 1 for overcurrent and 0 for no overcurrent
Bidirectional thyristor overcurrent signal:
boolean variables, 1 for overcurrent and 0 for no overcurrent
Bidirectional thyristor operating signal:
boolean variable, 1 for closed, 0 for open。
Assume that at the initial moment of monitoring, the open status signal of the protection switch K1 is 1 (indicating closed), and then the branch in which the protection switch K1 is located has a short-circuit fault. When the branch in which the protection switch K1 is located has a short-circuit fault, the bus voltage will decrease, and the overcurrent signal of the protection switch K1 is 1 (indicating overcurrent).
When the preset input control criterion is met, the predetermined control logic controls the bidirectional thyristor to execute closing operation. After the short-circuit current absorption branch bidirectional thyristor 10 is closed, the bidirectional thyristor 10 and the reactor 20 are connected to the bus in parallel.
After the short-circuit current absorbing branch is put into the power system, the short-circuit current of the branch where the protection switch K1 is located can be reduced or obviously reduced until the protection switch K1 is reliably switched off, so that the short-circuit fault of the branch where the K1 is located is isolated from the power system.
Then, the actions of the short-circuit current absorption branch exit control method based on voltage response when implemented in the substation power system shown in fig. 2 are as follows:
when the on-off state signal of the protection switch K1 is received and is 0 (indicating off), the bus voltage is detected to be increased to the preset threshold value U H And generating a short-circuit current absorption branch exit instruction.
The short-circuit current consumption branch withdrawing instruction, i.e. the bidirectional thyristor operating signal
The amplified signal (indicating the turn-off) is then transmitted to the control terminal of the triac 10 (so that the electrical characteristics of the signal match the thyristor), triggering the triac 10 to turn off.
After the triac 10 is turned off, the triac 10 is disconnected from the bus bar. The short circuit current absorbing branch exits from the power system.
In conclusion, the exit method can ensure that the short-circuit current control device exits in time by detecting the on-off state signal of the protection switch as off and the amplitude of the bus voltage, thereby being beneficial to reducing the measure amount aiming at the short-circuit fault and enabling the system to recover to the normal state earlier.
As shown in fig. 3, the short-circuit current absorption branch exit control method based on voltage response according to another embodiment of the present invention is implemented by the following two steps:
step 1: confirming the on-off state of a protection switch
(indicating disconnection)
The control unit 200 determines whether any of the plurality of fault protection switches is in the off state, that is, whether any of the plurality of fault protection switches is in the off state, based on the on/off state signals of all the plurality of branch circuits connected to the bus, which are acquired from the protection switch state acquisition unit 100
Whether it is equal to 0 (indicating open);
if it is used
If the signal is equal to 0, namely the on-off state signal of any fault protection switch is off, the next step is carried out; otherwise, stopping at the step and continuing to judge
Whether or not it is equal to 0.
Step 2: detecting whether the bus voltage is greater than a threshold value
Based on the bus voltage characteristic value U received from the voltage acquisition and processing component 300, the control component 200 determines whether the bus voltage U is higher than a voltage threshold value U H (U2 in FIG. 3), i.e., whether U > U is satisfied H ；
If U > U is satisfied H Then the control element 200 generates a short-circuit current absorption branch exit instruction;
the command driving element 400 receives this short-circuit current absorbing branch exit command and sends it to the power electronic switching device 10 in the short-circuit current absorbing branch, which disconnects it from the ac bus in response to the exit command, thus exiting the power system.
To avoid undue investment due to false alarms caused by spikes or other spurious signals in the voltage detection, it is preferred that U > U be satisfied for each of M consecutive detection periods H And then generating a short-circuit current absorption branch throwing-out instruction.
Preferably, U > U is satisfied for M consecutive detection periods H The number of cycles M1 is greater than the number of cycles satisfying U < U H At cycle number M2, a short circuit current absorption branch exit command is generated.
Preferably, the bus voltage characteristic value is smaller than the threshold value U in M continuous detection periods H And in the following continuous N detection periods, the characteristic value of the bus voltage is greater than the threshold value U H And generating a short-circuit current absorption branch exit instruction. Preferably, M is not greater than N.
Specifically, the duration of M consecutive detection periods is denoted as T1;
preferably, T1 ═ 20 ms; for reference, the update period of the three-phase bus voltage is 10 ms.
Specifically, the bus voltage characteristic value U is the minimum value of the effective values in the three-phase voltages.
Specifically, the bus voltage characteristic value U is the maximum value of the effective values in the three-phase voltages. .
Specifically, the bus voltage characteristic value U is a median, a geometric mean, or an arithmetic mean of effective values in the three-phase voltage.
Specifically, the bus voltage characteristic value U may be a weighted combination of various statistics such as a minimum value, a maximum value, a median value, a mathematical average value, or a geometric average value of each phase voltage in the three-phase voltage.
Specifically, the bus voltage characteristic value U is a geometric average value of each phase voltage in N consecutive measurement periods.
In specific implementation, the method can be flexibly selected according to indexes such as effectiveness, specificity and the like.
The setting voltage threshold value U will be described in detail below with reference to FIG. 2 H The step (2).
Suppose that N branches connected to the substation bus in fig. 2 are provided, and each branch is provided with a protection switch, which is denoted by K1, K2, and KN in sequence.
Step 21: and establishing a simulation model aiming at the topological structure of the plant station in the figure 2.
Step 22: through a simulation tool, a three-phase short circuit experiment is carried out on a branch where the protection switch K1 is located by using a simulation model, and a short circuit point which is closest to a bus outlet and can be independently switched off by the protection switch K1 and a corresponding bus voltage value are determined.
Specifically, through a simulation tool (such as power simulation tool software), a three-phase short circuit experiment is performed at each position of the branch where the protection switch K1 is located (note that the distances from the positions to the bus outlet are K1L1 and K1L2 in sequence, where K1L1 is greater than K1L 2):
1. at the beginning of the simulation, the length of the fault position from the bus bar outlet is set to be 50% of the total length of the line, and the length is an initial position.
2. From the initial position, three-phase short circuit experiments were performed round by round. In each round of short-circuit experiment, if the short-circuit current flowing through K1 is less than the maximum short-circuit current which can be switched off by K1, 1% of the total length of the line is reduced on the basis of the fault position of the current round, the fault position is taken as the fault position of the next round, and the three-phase short-circuit experiment is continued;
3. stopping the short-circuit experiment until the short-circuit current flowing through K1 is larger than the maximum short-circuit current which can be switched off by K1 in a certain round of short-circuit experiment; and the short-circuit current absorption branch is put into the power grid. After the short-circuit current absorption branch is put into a power grid, after the protection switch K1 is obtained to be disconnected, the voltage of the substation bus at the moment is recorded and recorded as U2K 1.
It can be seen that, in the above short circuit experiments, a method of reducing the distance between the short circuit point and the bus outlet by stepping with equal step length is adopted.
Through the steps, when the short-circuit fault occurs in the branch where the K1 is located at the maximum safe distance, the protection switch K1 is reliably disconnected, and the rising level of the bus voltage is isolated after the open-circuit fault.
The basic assumptions are: the closer the short-circuit fault point is to the bus bar outlet, the greater the short-circuit current that may be generated in that branch. The closer the short-circuit fault point is to the bus outlet, the larger the reduction amplitude of the bus voltage is. If the distance between the short-circuit point and the bus outlet is smaller than the safe distance, the protection switch cannot be safely disconnected, and a short-circuit current absorption branch needs to be put into the power grid to shunt so as to reduce the open-circuit current in the fault branch.
The closer the short-circuit fault point is to the bus outlet, the larger the bus voltage amplitude reduction is before fault isolation; after fault isolation, the bus voltage rising level is smaller after the short-circuit current absorption branch circuit is put into the power grid.
Step 23: and (3) repeating the step (22) for the branches where the rest of the protection switches are located by using a simulation model through a simulation tool, and respectively determining the corresponding bus voltage rising levels after the short circuit points which are closest to the bus outlets and can be independently disconnected from the protection switches K2 to KN and fault isolation.
Specifically, in the simulation tool, for the branches where the remaining protection switches K2 to KN are located, the step 22 is repeated, and U2K2 to U2KN are obtained in sequence.
Step 24: determining a voltage threshold value U applicable to the whole plant H In order to avoid the condition that the time for the short-circuit current absorption branch circuit to be put into the power grid is too long, the system is timely restored to a normal state, and a voltage threshold value U suitable for the whole plant station is determined H The minimum value of U2K1 to U2KN is as follows:
U H ＝min(U2K1，U2K2，·····，U2KN)
it should be understood that in the above steps, it is not limited that the simulation must start from K1; it is only necessary to perform a three-phase short circuit experiment for all the branches.
If the determined voltage threshold value U is determined H (i.e., U2) is U2K1, then U2K2, ·, U2KN determined by other branches are all larger than U2K 1.
That is, for the whole plant, as long as the bus voltage rises to U2, the short-circuit current absorbing branch will be disconnected from the power grid and enter into waiting for the next controllable input into the power grid.
The response is most effective for the branch in which K1 is located. For the other branch i, the short-circuit current absorbing branch can be separated from the power grid as long as the bus voltage reaches U2 and does not need to reach U2 Ki.
Whereas the bus is an ac bus, in particular, U2K1, U2K2, U2KN may be the minimum of the effective values of the three-phase voltages.
Specifically, the maximum value of the effective values in the three-phase voltage may be used.
Specifically, the median or the mathematical average of the effective values in the three-phase voltage may be used.
Specifically, the three-phase voltage may be a combination of various values such as a minimum value, a maximum value, a median value, or a geometric mean value of the voltages of the respective phases.
In specific implementation, the method can be flexibly selected according to indexes such as effectiveness, specificity and the like.
It should be understood that other principles may be used to adjust the rising side voltage threshold at which the short circuit current absorbing branch exits.
E.g., to determine a voltage threshold U applicable to the entire plant H Is the maximum value of U2K1 to U2KN, or a Mean value (Mean), or an average value (i.e., a mathematical average), or a combination of at least two of the above with a weighting factor.
In specific implementation, the method can be flexibly selected according to indexes such as effectiveness, specificity and the like.
In specific implementation, the three-phase bus voltage can be obtained from a measurement and control unit arranged in the intelligent substation by the voltage obtaining and processing element 300; a detection device for detecting the bus voltage may be additionally provided by the voltage acquisition and processing element 300.
In particular implementations, the voltage acquisition and processing element 300 may not be provided as a separate device. The control element 200 may obtain the bus voltage magnitude or relative magnitude from the intelligent substation.
In particular implementations, command driver component 400 may not be provided separately as a discrete device. When the electrical interface of the control element 200 may be matched with the electrical interface of the triac 10, the control element 200 may be directly connected to the triac 10, and directly send a short-circuit current absorption branch exit instruction to the triac.
In specific implementation, the protection switch state obtaining element 100 may not be separately provided as a discrete device. The control element 200 may obtain the open-state signal or the overcurrent state signal of each protection switch from the intelligent substation.
Specifically, each of the above power devices or switching devices is a high-voltage device, such as a short-circuit current of approximately 5-10KA, and a bus voltage of approximately 2200 KV.
The invention has been described above by reference to a few embodiments. However, other embodiments of the invention than the one disclosed above are equally possible within the scope of the invention, as would be apparent to a person skilled in the art from the appended patent claims.
Generally, all terms used in the claims are to be interpreted according to their ordinary meaning in the technical field, unless explicitly defined otherwise herein. All references to "a/an/the [ means, component, etc ]" are to be interpreted openly as referring to at least one instance of said means, component, etc., unless explicitly stated otherwise. The steps of any method disclosed herein do not have to be performed in the exact order disclosed, unless explicitly stated.
Claims (8)
1. A short-circuit current absorption branch exit control method based on voltage response is characterized by comprising the following steps:
when detecting that the monitored voltage characteristic value of the alternating current bus is higher than a preset voltage threshold value, generating a short-circuit current absorption branch exit instruction, wherein the short-circuit current absorption branch exit instruction comprises the following steps: when any fault protection switch in all the branches connected in parallel with the bus voltage is disconnected according to the obtained disconnection state, and when the voltage characteristic value of the monitored alternating current bus is detected to be higher than a preset voltage threshold value, generating a short-circuit current absorption branch exit instruction;
the short-circuit current absorption branch circuit is a shunt branch circuit which is connected with the bus in parallel and can be controllably switched into or switched out of the power grid;
and responding to the short-circuit current consumption branch exit instruction, and controlling the short-circuit current consumption branch to exit from the power grid.
2. The exit control method according to claim 1,
the detecting that the monitored voltage characteristic value of the alternating-current bus is higher than a preset voltage threshold value comprises the following steps:
and in M continuous detection periods, detecting that the voltage characteristic value of the monitored alternating-current bus is higher than a preset voltage threshold value, wherein M is a positive integer.
3. The exit control method according to claim 1,
the detecting that the monitored voltage characteristic value of the alternating-current bus is higher than a preset voltage threshold value comprises the following steps:
in M continuous detection periods, the detection period number M1 meeting the condition that the voltage characteristic value is higher than the preset voltage threshold value is larger than the detection period number M2 meeting the condition that the voltage characteristic value is not higher than the preset voltage threshold value, wherein M is a positive integer, M1 is a positive integer, and M2 is a positive integer.
4. The exit control method according to claim 1,
the detecting that the monitored voltage characteristic value of the alternating-current bus is higher than a preset voltage threshold value comprises the following steps:
in M continuous detection periods, the characteristic value of the bus voltage is lower than a preset voltage threshold value;
and in the following continuous N detection periods, the bus voltage characteristic value is higher than a preset voltage threshold value, wherein M is not more than N, M is a positive integer, and N is a positive integer.
5. The exit control method according to claim 1,
the short-circuit current absorption branch comprises a bidirectional thyristor which is controllably connected with or disconnected from the bus;
and the reactor is connected with the bidirectional thyristor in series and is grounded.
6. A voltage response-based short-circuit current absorption branch exit control device is characterized by comprising:
the voltage characteristic value acquisition element is used for detecting the voltage characteristic value of the monitored alternating current bus;
the control element is used for generating a short-circuit current absorption branch exit instruction when detecting that the monitored voltage characteristic value of the alternating current bus is higher than a preset voltage threshold value, and comprises the following steps: when any fault protection switch in all the branches connected in parallel with the bus voltage is disconnected according to the obtained disconnection state, and when the voltage characteristic value of the monitored alternating current bus is detected to be higher than a preset voltage threshold value, generating a short-circuit current absorption branch exit instruction;
the instruction driving element is used for receiving the short-circuit current absorption branch exit instruction and sending the short-circuit current absorption branch exit instruction to the short-circuit current absorption branch so that the short-circuit current absorption branch exits from the power grid in response to the short-circuit current absorption branch exit instruction;
the short-circuit current absorption branch circuit is a shunt branch circuit which is connected with the bus in parallel and can be controllably switched into or switched out of the power grid.
7. The control device according to claim 6, characterized by further comprising:
the protection switch state acquisition element is used for receiving and processing the on-off signal of the protection switch;
the control element is further used for generating a short-circuit current absorbing branch exit instruction when the on-off state of any fault protection switch in all the branches connected in parallel with the bus voltage is off and when the monitored voltage characteristic value of the alternating current bus is detected to be higher than a preset voltage threshold value.
8. The control device according to claim 6, characterized by further comprising:
the short-circuit current absorption branch comprises a bidirectional thyristor which is controllably connected with or disconnected from the bus;
and the reactor is connected with the bidirectional thyristor in series and is grounded.
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| CN205646794U (en) * | 2016-05-12 | 2016-10-12 | 安徽尚途电力保护设备有限公司 | Explosion bridge type generating line residual voltage holding device |
| CN106849039A (en) * | 2017-03-02 | 2017-06-13 | 安徽伊格瑞德电气设备有限公司 | A kind of novel bus residual voltage holding meanss |
| CN107623308A (en) * | 2017-08-21 | 2018-01-23 | 南方电网科学研究院有限责任公司 | A kind of suppressing method and system of AC network short circuit currents |
| CN108493917B (en) * | 2018-03-23 | 2019-06-21 | 湖南大学 | Novel aerial drainage control device |
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| CN105896488A (en) * | 2016-04-29 | 2016-08-24 | 浙江大学 | Short circuit fault processing method for flexible DC power grid based on combined-type high-voltage DC circuit breaker |
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