CN109962448B - Short-circuit current absorption branch input control method and device based on voltage characteristics - Google Patents
Short-circuit current absorption branch input control method and device based on voltage characteristics Download PDFInfo
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- CN109962448B CN109962448B CN201910106637.1A CN201910106637A CN109962448B CN 109962448 B CN109962448 B CN 109962448B CN 201910106637 A CN201910106637 A CN 201910106637A CN 109962448 B CN109962448 B CN 109962448B
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H3/00—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection
- H02H3/02—Details
- H02H3/025—Disconnection after limiting, e.g. when limiting is not sufficient or for facilitating disconnection
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
- H02H7/26—Sectionalised protection of cable or line systems, e.g. for disconnecting a section on which a short-circuit, earth fault, or arc discharge has occured
- H02H7/261—Sectionalised protection of cable or line systems, e.g. for disconnecting a section on which a short-circuit, earth fault, or arc discharge has occured involving signal transmission between at least two stations
- H02H7/262—Sectionalised protection of cable or line systems, e.g. for disconnecting a section on which a short-circuit, earth fault, or arc discharge has occured involving signal transmission between at least two stations involving transmissions of switching or blocking orders
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Abstract
The invention provides a short-circuit current absorption branch circuit input control method and device based on voltage response characteristics. When the monitored voltage characteristic value of the alternating current bus is detected to be lower than a preset voltage threshold value, generating a short-circuit current absorption branch input instruction; and responding to the short-circuit current absorption branch input instruction, and controlling the short-circuit current absorption branch to be input into a power grid. The method provided by the invention generates the short-circuit current consumption branch circuit input instruction based on the level change of the busbar voltage before and after the fault, can effectively reduce the short-circuit current level of the short-circuit point, ensures that the fault protection switch is reliably disconnected and isolated from the fault, thereby providing enough short-circuit capacity for the normal operation of the power grid and ensuring the safe and stable operation of the power grid.
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 input of a short-circuit current absorption branch circuit based on voltage response characteristics.
Background
With the continuous expansion of the power grid scale in China, the grid is more and more dense, and the short-circuit current level of the system is also increased sharply. If the short-circuit current exceeds the breaking capacity of the protection switch, the protection switch cannot break the short-circuit current, so that faults cannot be isolated, and further serious accidents such as line and equipment burnout, system stability damage and the like are caused. Therefore, effective measures must be taken to actually reduce the short-circuit current level.
The current common means comprise optimizing a grid structure, stopping a line, adding a fault current limiter and the like. The methods can influence the system safety, or have low reliability, high false alarm rate and poor current limiting effect.
Disclosure of Invention
The invention provides a short-circuit current absorption branch circuit input control method and device based on voltage response characteristics, which are used for reducing the safety risk of a power grid caused by overlarge short-circuit current in a local area at present.
In a first aspect, the present invention provides a method for controlling input of a short-circuit current absorption branch circuit based on voltage response, including:
when the monitored voltage characteristic value of the alternating current bus is detected to be lower than a preset voltage threshold value, generating a short-circuit current absorption branch circuit input instruction;
the short-circuit current absorption branch is a shunt branch which is parallel to the bus and can be controllably thrown into or withdrawn from the power grid;
and responding to the short-circuit current absorption branch input instruction, and controlling the short-circuit current absorption branch to be input into a power grid.
In particular to a method for controlling the input,
the detecting that the voltage characteristic value of the monitored alternating current bus is lower than a preset voltage threshold value comprises the following steps:
in the continuous M detection periods, the voltage characteristic value of the monitored alternating current bus is detected to be lower than a preset voltage threshold value, and M is a positive integer.
Specifically, the input control method, the detecting that the voltage characteristic value of the monitored ac bus is lower than a preset voltage threshold value, includes:
in the continuous M detection periods, the characteristic value of the bus voltage is higher than a preset voltage threshold value;
in the subsequent continuous N detection periods, the characteristic value of the bus voltage is lower than a preset voltage threshold value, wherein N is not smaller than M, M is a positive integer, and N is a positive integer.
Specifically, the input control method further comprises the following steps:
and generating a short-circuit current absorption branch circuit input instruction when the overcurrent state of any fault protection switch in all the branches connected with the bus voltage in parallel is overcurrent and when the monitored voltage characteristic value of the alternating current bus is detected to be lower than a preset voltage threshold value.
Specifically, the input control method further comprises the following steps:
after the short-circuit current absorption branch circuit input instruction is generated, when a preset delay time T2 is reached, a short-circuit current absorption branch circuit exit instruction is generated,
and responding to the short-circuit current absorption branch exit instruction, and controlling the short-circuit current absorption branch to exit from the power grid.
In particular to a method for controlling the input,
the short-circuit current absorption branch comprises a bidirectional thyristor which is used for controllably connecting or disconnecting with a 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 circuit input instruction when detecting that the voltage characteristic value of the monitored alternating current bus is lower than a preset voltage threshold value.
Specifically, the control device further comprises:
the command driving element is used for receiving the short-circuit current absorption branch input command and sending the short-circuit current absorption branch input command to the short-circuit current absorption branch so that the short-circuit current absorption branch responds to the short-circuit current absorption branch input command and inputs the short-circuit current absorption branch input command into a power grid;
the short-circuit current absorption branch is a shunt branch which is parallel to the bus and can be controllably thrown into or withdrawn from the power grid.
Specifically, the control device further comprises:
the protection switch state acquisition element is used for receiving and processing an overcurrent signal of the protection switch;
the control element is also used for generating a short-circuit current absorption branch input instruction when the overcurrent state of any fault protection switch in all branches connected in parallel with the bus voltage is overcurrent and when the monitored voltage characteristic value of the alternating current bus is detected to be lower than a preset voltage threshold value.
Specifically, the control device further comprises:
a short-circuit current absorption branch comprising a bidirectional thyristor for controllably connecting or disconnecting with a bus;
and the reactor is connected with the bidirectional thyristor in series and is grounded.
According to the voltage response-based short-circuit current absorption branch input control method and device, the short-circuit current absorption branch input instruction is generated based on the level change of the busbar voltage before and after the fault, so that the short-circuit current level of a short-circuit point can be effectively reduced, the fault protection switch is ensured to be reliably disconnected and isolated from the fault, and therefore a large enough short-circuit capacity is provided for normal operation of a power grid, and safe and stable operation of the power grid is ensured.
Drawings
Exemplary embodiments of the present invention may be more completely understood in consideration of the following drawings:
FIG. 1 is a schematic flow chart of a method for switching a short-circuit current absorption branch circuit based on voltage response according to a preferred embodiment of the invention;
FIG. 2 is a schematic diagram showing the composition of a short-circuit current control device based on voltage response according to a preferred embodiment of the present invention;
FIG. 3 is a flow chart of another embodiment of a method for switching a short-circuit current absorption branch based on voltage response;
FIG. 4 is a flow chart of another embodiment of a method for exiting a short circuit current sink leg based on voltage response;
fig. 5 is a waveform diagram of the bus voltage at the time of a short-circuit fault in the preferred embodiment of the present invention.
Detailed Description
The exemplary embodiments of the present invention will now be described with reference to the accompanying drawings, however, the present invention may be embodied in many different forms and is not limited to the examples described herein, which are provided to fully and completely disclose the present invention and 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, like elements/components are referred to by like reference numerals.
Unless otherwise indicated, terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art. In addition, it will be understood that terms 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 the next-stage voltage power grid exceeds the standard is common. When any branch on the ac bus of the substation shown in fig. 2 has a short-circuit fault, measures for limiting the short-circuit current need to be adopted in time to ensure that the fault protection switch is reliably opened and isolate the fault in time. After fault isolation, measures for limiting short-circuit current need to be withdrawn in time, so that the system is restored to a normal state as soon as possible.
It should be understood that, when the short-circuit fault occurs in the branch, the fault protection switch K keeps closed when the flowing short-circuit current is greater than the maximum short-circuit current that can be opened, but continuously detects the short-circuit current in real time; the short-circuit protection switch is opened until the flowing short-circuit current is reduced to be not more than the maximum short-circuit current which can be opened; and after the fault is eliminated, the fault protection switch is closed and waits for the response of the next fault.
Specifically, the protection switch comprises a body and a control element, wherein the control element controls the local switch to be opened or closed, generates an overcurrent state signal or an open state signal, and provides the overcurrent state signal or the open state signal for other power system devices to perform state monitoring or logic judgment. As shown in fig. 2, the short-circuit current absorption branch is installed on a bus of a station to be detected (such as a transformer substation). The short-circuit current absorption branch comprises a power electronic switching device 10 controllably connected with or disconnected from a bus bar, and a reactor 20 connected in series with the power electronic switching device, wherein the reactor 20 is reliably grounded.
The short-circuit current-dissipating branch is equivalent to a shunt branch which is controllably connected to the bus bar in case of a short-circuit fault in the power network. In particular, the short-circuit current-dissipating branch is withdrawn from the grid or the current value taken from the bus bar is approximately zero before a short-circuit fault occurs in the grid.
After a short circuit fault occurs in the power grid, the short circuit current absorption branch is controllably input into the power grid, and a larger first current value is obtained from a bus before a protection switch of the short circuit branch is not disconnected; after the protective switch of the short-circuit branch is opened, a larger second current value is obtained from the bus bar, wherein the second current value is larger than the first current value.
After the protection switch of the short-circuit branch has reliably opened, the short-circuit fault is isolated. In this case, the short-circuit current-dissipating branch needs to be withdrawn from the network in a controlled manner, or the current value taken from the bus bar is approximately zero.
According to the short-circuit current absorption branch circuit input control method and the short-circuit current control device based on the voltage response, the short-circuit current absorption branch circuit input instruction is generated based on the level change of the busbar voltage before and after the fault, the short-circuit current level of a short-circuit point can be effectively reduced, the fault protection switch is ensured to be reliably disconnected and isolated from the fault, and therefore a large enough short-circuit capacity is provided for normal operation of a power grid, and safe and stable operation of the power grid is ensured.
Specifically, when the short-circuit current absorption branch is controlled to be connected with the bus, the probability of early connection needs to be reduced to the minimum as much as possible; and the probability of delayed connection is minimized.
As shown in fig. 1, a short-circuit current absorption branch input control method based on voltage response according to a preferred embodiment of the present invention includes:
step S100: when the monitored voltage characteristic value of the alternating current bus is detected to be lower than a preset voltage threshold value, generating a short-circuit current absorption branch circuit input instruction;
the short-circuit current absorption branch is a shunt branch which is parallel to the bus and can be controllably thrown into or withdrawn from the power grid;
step S200: and responding to the short-circuit current absorption branch input instruction, and controlling the short-circuit current absorption branch to be input into a power grid.
It should be understood that the detection herein may include one detection period or may include a plurality of detection periods in succession. The detection period can be an update period of updating voltage quantity and current quantity of each measurement and control element in the intelligent substation, or can be a sampling period of acquiring voltage signals by the voltage characteristic value acquisition element; and may also include time consuming transmissions over the communications link.
In particular to a method for controlling the input,
the detecting that the voltage characteristic value of the monitored alternating current bus is lower than a preset voltage threshold value comprises the following steps:
in the continuous M detection periods, the voltage characteristic value of the monitored alternating current bus is detected to be lower than a preset voltage threshold value, and 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 is detected to be lower than a preset voltage threshold value in continuous M detection periods, the voltage is considered to have fallen to an adverse level which affects the safety and stability of the system, measures for reducing short-circuit current must be put into operation as soon as possible, so that the fault protection switch is ensured to be reliably opened, and the short-circuit fault is reliably isolated.
The method has more information quantity introduced and more comprehensive criteria, so that the method has good reliability and low misoperation probability.
Specifically, the input control method, the detecting that the voltage characteristic value of the monitored ac bus is lower than a preset voltage threshold value, includes:
in the continuous M detection periods, the characteristic value of the bus voltage is higher than a preset voltage threshold value;
in the subsequent continuous N detection periods, the characteristic value of the bus voltage is lower than a preset voltage threshold value, wherein N is not smaller than M, M is a positive integer, and N is a positive integer.
In order to avoid the risk of judging based on the absolute value, the bus voltage characteristic value is higher than a preset voltage threshold value in M continuous detection periods; in the subsequent continuous N detection periods, when the characteristic value of the bus voltage is lower than a preset voltage threshold, the voltage is considered to have a definite descending trend and has fallen to an adverse level affecting the safety and stability of the system, and measures for reducing the short-circuit current must be put into operation as soon as possible so as to ensure that the fault protection switch is reliably opened and the short-circuit fault is reliably isolated.
The method has more information quantity introduced and more comprehensive criteria, so that the method has good reliability and low misoperation probability.
Specifically, the input control method further comprises the following steps:
and generating a short-circuit current absorption branch circuit input instruction when the overcurrent state of any fault protection switch in all the branches connected with the bus voltage in parallel is overcurrent and when the monitored voltage characteristic value of the alternating current bus is detected to be lower than a preset voltage threshold value.
The method is based on the fact that the protection switch on the branch is in an overcurrent state when a short circuit fault occurs, combines the overcurrent state of the protection switch with a voltage drop criterion, ensures that measures for reducing short circuit current must be put into as soon as possible when the protection switch fails to be opened in time and the voltage drops to an unfavorable level affecting the safety and stability of the system, so as to ensure that the fault protection switch is reliably opened and the short circuit fault is reliably isolated.
The method has more information quantity introduced and more comprehensive criteria, so that the method has good reliability and low misoperation probability.
Specifically, the input control method further comprises the following steps:
after the short-circuit current absorption branch circuit input instruction is generated, when a preset delay time T2 is reached, a short-circuit current absorption branch circuit exit instruction is generated,
and responding to the short-circuit current absorption branch exit instruction, and controlling the short-circuit current absorption branch to exit from the power grid.
In particular to a method for controlling the input,
the short-circuit current absorption branch comprises a bidirectional thyristor which is used for controllably connecting or disconnecting with a bus;
and the reactor is connected with the bidirectional thyristor in series and is grounded.
As shown in fig. 2, a short-circuit current control device based on voltage response according to a 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 circuit input instruction when detecting that the voltage characteristic value of the monitored alternating current bus is lower than a preset voltage threshold value.
Specifically, the control device further comprises:
the command driving element is used for receiving the short-circuit current absorption branch input command and sending the short-circuit current absorption branch input command to the short-circuit current absorption branch so that the short-circuit current absorption branch responds to the short-circuit current absorption branch input command and inputs the short-circuit current absorption branch input command into a power grid;
the short-circuit current absorption branch is a shunt branch which is parallel to the bus and can be controllably thrown into or withdrawn from the power grid.
Specifically, the control device further comprises:
the protection switch state acquisition element is used for receiving and processing an overcurrent signal of the protection switch;
the control element is also used for generating a short-circuit current absorption branch input instruction when the overcurrent state of any fault protection switch in all branches connected in parallel with the bus voltage is overcurrent and when the monitored voltage characteristic value of the alternating current bus is detected to be lower than a preset voltage threshold value.
Specifically, the control device further comprises:
a short-circuit current absorption branch comprising a bidirectional thyristor for controllably connecting or disconnecting with a 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 can also control the short-circuit current absorption branch to be separated from the bus (also comprising the situation that the current value obtained from the bus is approximately zero), so that measures for reducing short-circuit current (namely, throwing the short-circuit current absorption branch) can be withdrawn from the power system in time after short-circuit fault isolation in the power system, and the safe and stable operation of the power grid is ensured.
It should be understood that the short-circuit current-dissipating branch shown in fig. 2 is equivalent to a reactor controllably connected to or disconnected from a bus bar. The power electronic switching devices controlling the reactor to be connected to or disconnected from the bus bar are various, and the electric connection modes of the power electronic switching devices and the reactor are various and are well known to those skilled in the art, and are not described herein.
Typically, the short-circuit current-dissipating branch and the corresponding short-circuit current control device are deployed in a single plant as a minimum unit. In this case, the component characteristics and parameters of the short-circuit current absorption branch, the parameters of the short-circuit current control device and the control logic are respectively adapted to the individual plant.
Preferably, the power supplyThe sub-switching device is a triac. As a power electronic device that can operate with high power currents or voltages, a triac may also provide a status signal that is tied to the current level and/or an on-off status signal that characterizes on (i.e., closed) or off (i.e., open) in real time. After parameter adaptation with the target loop or the power system, the bidirectional thyristor corresponds to a rated current I 1 And an overcurrent I 2 . After the bidirectional thyristor is closed, when the connected working current is lower than the overcurrent I 2 The triac over-current status signal is 0 (indicating no over-current). After the bidirectional thyristor is closed, the working current is higher than the overcurrent I 2 The triac over-current status signal is 1 (indicating over-current) at this time.
As shown in fig. 2, the short-circuit current control device according to the preferred embodiment of the present invention can cover all branches and protection switches thereof at the outlet of a bus of a plant.
Before and after a short-circuit fault and fault isolation occurs on any branch in the plant, the value of the working current connected to the bidirectional thyristor is lower than the rated current I in the first stage of closing the protection switch and closing the bidirectional thyristor (at the moment, the short-circuit current absorption branch is put into the power grid) 1 The method comprises the steps of carrying out a first treatment on the surface of the In the second stage of opening the protection switch and closing the bidirectional thyristor (at this time, the short-circuit current absorbing branch is put into the power grid), the working current of the bidirectional thyristor is higher than the overcurrent I 2 The method comprises the steps of carrying out a first treatment on the surface of the In the third stage of the opening of the protection switch and the disconnection of the triac (at this time, the short-circuit current-dissipating branch is withdrawn from the network), the value of the operating current supplied by the triac is much lower than the rated current I 1 。
As shown in fig. 5, the bus voltage level continuously drops at the stage of the protection switch closing, the bidirectional thyristor opening and the protection switch overcurrent (at this time, the short-circuit current absorption branch is not put into the power grid) before and after the short-circuit fault and fault isolation occur on any branch in the plant; the bus voltage level gradually drops at the stage of closing the protection switch, closing the bidirectional thyristor and overcurrent the protection switch (at this time, the short-circuit current absorbing branch circuit is put into the power grid); the bus voltage level continuously rises in the stage of opening the protection switch and closing the bidirectional thyristor (at the moment, the short-circuit current absorption branch circuit is put into the power grid); the bus voltage level remains in normal operation during the phases of protection switch opening, triac opening (at which point the short-circuit current dissipating branch exits from the grid).
When the short-circuit current absorption branch is controlled to be separated from the power system, the short-circuit fault measure is required to be ensured not to be cut by mistake and not to be cut in advance. The probability of early exit is minimized; the probability of delayed exit is also minimized. At this time, the fault protection switch is turned off as a key condition for ensuring that the fault protection switch is not cut in advance; and the recovery of the bus voltage is a key condition without delay.
According to the method provided by the embodiment of the invention, after the short-circuit protection switch of the fault branch circuit has been reliably disconnected and the bus voltage has fallen to the allowable value, the short-circuit current absorption branch circuit is controlled to be disconnected from the bus.
The following are term descriptions and symbol definitions:
protection switch status signal:
boolean variable, 1 for closed, 0 for open
Protection switch overcurrent signal:
boolean variable, 1 for overcurrent, 0 for overcurrent
Bidirectional thyristor overcurrent signal:
boolean variable, 1 for overcurrent, 0 for overcurrent
Bidirectional thyristor action signal:
boolean variable, 1 indicates closed, 0 indicates open.
At the initial time of monitoring, the on-off state signal of the protection switch K1
1 (indicating closure) and then the branch in which the protection switch K1 is located suffers a short-circuit fault. When the branch where 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 preset control logic controls the bidirectional thyristor to execute the closing operation. After the triac 10 of the short-circuit current absorption branch is closed, the triac 10 and the reactor 20 are connected to the bus in parallel.
After the short-circuit current absorption branch circuit is put into the power system, the short-circuit current of the branch circuit where the protection switch K1 is located can be reduced or obviously reduced until the protection switch K1 is reliably disconnected, so that the short-circuit fault of the branch circuit where the protection switch K1 is located is isolated from the power system.
Specifically, when the branch where the protection switch K1 is located has a short circuit fault, the three-phase minimum voltage is generated on the bus of the transformer substation
Below threshold value U L And the duration exceeds T1; meanwhile, the branch where K1 is located has larger short-circuit current, so that the overcurrent protection signal of the protection switch K1 is +.>
When the current becomes 1 (indicating overcurrent), a short-circuit current consumption branch circuit input command is generated.
The short circuit current dissipates the input instruction of the branch circuit and the action signal of the bidirectional thyristor
(indicating closure) is amplified and fed to the control terminal of the triac 10 (such that the electrical characteristics of the signal match that of the thyristor), triggering the triac 10 to close.
After the triac 10 is closed, the triac 10 and the reactor 20 are connected in parallel to the bus. After the short-circuit current absorption branch circuit is put into the power system, the short-circuit current of the branch circuit where the protection switch K1 is located can be reduced or obviously reduced until the protection switch K1 is reliably disconnected, so that the short-circuit fault of the branch circuit where the protection switch K1 is located is isolated from the power system.
Subsequently, after the short-circuit current consumption branch input instruction is generated, the control element 200 generates a short-circuit current consumption branch exit instruction after a preset delay time T2 is reached.
The short-circuit current dissipates the branch exit instruction, i.e. the bidirectional thyristor action signal
(indicating off) is amplified and then fed to the control terminal of the triac 10 (such that the electrical characteristics of the signal match that of 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-dissipating branch exits from the power system.
At this time, the short-circuit current real-time control device is in a state of being able to respond to the short-circuit faults of other branches on the bus of the transformer substation again.
In summary, by detecting the overcurrent signal of the protection switch K1
And/or bus voltage->
The short-circuit current absorption branch circuit can be ensured to be reliably put into in time.
As shown in fig. 3, when determining whether a short-circuit current absorption loop is input, the voltage response-based short-circuit current real-time control device according to the embodiment of the invention includes the following steps:
step 1: confirming existence of protection switch overcurrent signal in loop
(indicating overcurrent)
According to the slave protection switch shapeThe state acquisition element 100 receives the protection switch overcurrent signal, and the control element 200 determines whether one protection switch overcurrent signal exists in the loop to satisfy the following condition
(indicating overcurrent), if yes, go to step 2;
otherwise, the control element 200 continues to receive and determine whether the protection switch overcurrent signal is satisfied
It should be understood herein that the control element 200 logically or processes the plurality of protection switch over-current signals received from the protection switch state acquisition element 100, so long as one protection switch over-current signal satisfies
(indicating an overcurrent) it can be determined that a short circuit fault has occurred in the current bus.
Step 2: detecting whether the bus voltage is lower than a threshold value
Based on the characteristic value U of the bus voltage received from the voltage acquisition and processing device 300, the control device 200 determines whether the bus voltage U is lower than the threshold value U L (U1 in FIG. 3), i.e. whether U < U is satisfied L ；
If U is less than U L The control element 200 generates a short-circuit current consumption branch input instruction;
the command driving element 400 receives the short-circuit current consuming branch input command and sends it to the power electronic switching device 10 in the short-circuit current consuming branch, which, in response to the input command, taps the short-circuit current consuming branch to the ac bus.
Specifically, the bus voltage characteristic value U is the minimum effective value of the three-phase voltages
Specifically, the bus voltage characteristic value U is a geometric average value of the voltages of the respective phases in the continuous N measurement periods.
In order to avoid improper investment due to spikes or other artifacts in the voltage detection, preferably U < U is satisfied during consecutive M detection periods L And generating a short-circuit current absorption branch circuit input instruction.
Preferably, U < U is satisfied during consecutive M detection periods L The cycle number M1 of the catalyst is greater than the value that U is not less than U L And (3) generating a short-circuit current absorption branch input instruction during the period number M2.
Preferably, the characteristic value of the bus voltage is greater than the threshold value U in M continuous detection periods L And in the following continuous N detection periods, the characteristic values of the bus voltage are smaller than the threshold value U L Generating a short-circuit current absorption branch circuit input instruction. Preferably, M is not less than N.
Specifically, the duration of the consecutive M detection periods is noted as T1;
preferably, t1=20 ms; for reference, the update period of the three-phase bus voltage is 10ms.
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.
The setting threshold value U will be described in detail below with reference to FIG. 2 L Is carried out by a method comprising the steps of. In fig. 2, the number of branches connected with the bus of the transformer substation is assumed to be N, and each branch is provided with a protection switch which is sequentially denoted as K1, K2, & gtKN.
Step 11: a simulation model is built for the topology of the plant in fig. 2.
Step 12: through simulation tools, three-phase short-circuit experiments are carried out on the branch where the protection switch K1 is located by using simulation models, and the nearest short-circuit point and the corresponding bus voltage value, which are the closest to the bus outlet, of the protection switch K1 can be independently opened and closed are determined.
Specifically, through simulation tools (such as electric simulation tool software), three-phase short-circuit experiments are performed at each position of the branch where the protection switch K1 is located (where the distances between each position and the bus outlet are K1L1 and K1L2 in sequence, where K1L1 is greater than K1L 2):
1. at the start of the simulation, the length of the fault location from the bus bar outlet was set to be 50% of the full length of the line, which is the initial location.
2. Starting from the initial position, three-phase short-circuit experiments are carried out round by round. In the short-circuit experiment of each round, if the short-circuit current flowing through K1 is smaller than the maximum short-circuit current which can be disconnected by K1, reducing the total length of the line by 1% on the basis of the fault position of the current round, taking the reduced total length of the line as the fault position of the next round, and continuing the three-phase short-circuit experiment;
3. and stopping the short-circuit experiment until the short-circuit current flowing through K1 is larger than the maximum short-circuit current which can be opened and closed by K1 in a short-circuit experiment of a certain round. The bus voltage of the transformer substation at this time is recorded as U1K1.
It can be seen that the short-circuit experiment of each round adopts a method of reducing the distance between the short-circuit point and the bus outlet in a stepping way with equal step length.
In view of the bus being an ac bus, in particular, U1K1 may be the minimum of the effective values in the three-phase voltages.
Specifically, U1K1 may be the maximum value of the effective values in the three-phase voltages.
Specifically, U1K1 may be the median or mathematical average of the effective values in the three-phase voltages.
Specifically, U1K1 may be a combination of various values such as a minimum value, a maximum value, a median value, or a geometric average value of each phase voltage among the three phase voltages.
In the specific embodiment, the method is flexibly selected according to indexes such as effectiveness, specificity and the like.
Through the steps, when the short-circuit fault occurs to the branch where the protection switch K1 is located, the protection switch K1 can be independently opened and closed to the farthest short-circuit point, namely the largest safety distance, at the bus outlet.
That is, the closer the short circuit fault point is to the bus bar outlet, the greater the short circuit current that may be generated in the branch. The closer the short-circuit fault point is to the bus outlet, the larger the decrease of the bus voltage.
If the distance between the short-circuit point and the bus outlet is smaller than the safety distance, the protection switch cannot be safely disconnected, and a short-circuit current absorption branch is needed to be thrown into the power grid to be shunted so as to reduce the short-circuit current in the fault branch.
Step 13: and (3) repeating the step 12 for the branches where the rest protection switches K2 to KN are located by using a simulation model through a simulation tool, and respectively determining the farthest short-circuit point and the corresponding bus voltage at the bus outlet where the protection switches K2 to KN can be independently opened.
Specifically, in the simulation tool, for the branches where the protection switches from K2 to KN are located, step 12 is repeated, and U1K2 to U1KN are sequentially obtained.
Step 14: determining a threshold value U applicable to an entire plant L
In order to avoid frequent input of short-circuit current absorption branches, a threshold value U applicable to the whole plant is determined on the basis of minimum guarantee L Is the minimum value of U1K1 to U1KN, and has the following formula:
U L ＝min(U1K1，U1K2，·····，U1KN)
it should be understood that in the above steps, the simulation is not limited to have to start from K1; as long as the three-phase short-circuit experiment is performed for all the branches.
In view of the bus being an ac bus, in particular, U1K1, U1K2, U1KN may be the minimum of the effective values in the three-phase voltage.
Specifically, the maximum value of the effective values in the three-phase voltages may be used.
In particular, it may be a median or mathematical average of the effective values in the three-phase voltages.
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 average value of each phase voltage among the three-phase voltages.
In the specific implementation, the method is flexibly selected according to indexes such as effectiveness, specificity and the like.
It should be understood that other principles may be employed to adjust the threshold value U of the short-circuit current absorption branch input L 。
For example, to determine a threshold value U applicable to the whole plant L Is the maximum value of U1K1 to U1KN, or the median value (Mean), or the average value (i.e., mathematical average value), or a combination of at least two of the foregoing, with a weighting coefficient.
In the specific implementation, the method is flexibly selected according to indexes such as effectiveness, specificity and the like.
Then, the following actions are performed when the short-circuit current consumption branch exit control method based on the voltage response is implemented in the substation power system shown in fig. 2:
when receiving the on-off state signal of the protection switch K1
Is 0 (indicating disconnection), and the rise of the bus voltage to a preset threshold value U is detected H And generating a short-circuit current absorption branch exit instruction. />
The short-circuit current dissipates the branch exit instruction, i.e. the bidirectional thyristor action signal
(indicating off) is amplified and then fed to the control terminal of the triac 10 (such that the electrical characteristics of the signal match that of the thyristor), triggering the triac 10 to turn off.
After the triac 10 opens, the triac 10 is disconnected from the bus bar and the short circuit current dissipating branch exits from the power system.
In summary, the input method can ensure that the short-circuit current control device exits in time by detecting the opening state signal of the protection switch as the opening and the amplitude of the bus voltage, thereby being beneficial to reducing the measure against the short-circuit fault and leading the system to recover to the normal state earlier.
As shown in fig. 4, the method for controlling the exit of the short-circuit current absorption branch based on voltage response according to another embodiment of the invention is completed by the following two steps:
step 1: confirming the on-off state of the protection switch
(indicating disconnection)
Based on the on-state signals of all the protection switches in the plurality of branches connected to the bus bar, which are acquired from the protection switch state acquisition element 100, the control element 200 determines whether any of the short-circuit protection switches is in the off state, that is
Whether or not equal to 0 (indicating disconnection);
if it is
Equal to 0, namely, if the on-off state signal of any short-circuit protection switch is off, entering the next step; otherwise stay in this step, continue 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 element 300, the control element 200 determines whether the bus voltage U is higher than the voltage threshold value U H (U2 in FIG. 4), i.e., whether U > U is satisfied H ；
If U is more than U H The control element 200 generates a short-circuit current consumption branch exit instruction;
the command driving element 400 receives the short-circuit current consuming branch exit command and sends it to the power electronic switching device 10 in the short-circuit current consuming branch, which in response to the exit command disconnects the short-circuit current consuming branch from the ac bus, thereby exiting the power system.
In order to avoid improper exit due to false alarms caused by spikes or other artifacts in the voltage detection, preferably U > U is satisfied during consecutive M detection periods H And generating a short-circuit current absorption branch throwing and exiting instruction.
Preferably, during consecutive M test cyclesIn the period, satisfy U > U H The cycle number M1 is greater than the value satisfying U < U H And (3) generating a short-circuit current absorption branch exit instruction during the period number M2.
Preferably, the bus voltage characteristic values are smaller than the threshold value U in the continuous M detection periods H And in the following continuous N detection periods, the characteristic values of the bus voltage are all larger than a 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 the consecutive M detection periods is noted as T1;
preferably, t1=20 ms; for reference, the update period of the three-phase bus voltage is 10ms.
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 average, or an arithmetic average of effective values in the three-phase voltages.
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 voltages.
Specifically, the bus voltage characteristic value U is a geometric average value of the voltages of the respective phases in the continuous N measurement periods.
In the specific implementation, the method is 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, 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 the relative magnitude from the intelligent substation.
In particular implementations, command driving element 400 may not be provided as a separate device. When the electrical interface of the control element 200 can be matched with the electrical interface of the triac 10, the control element 200 can be directly connected with the triac 10, and directly sends a short-circuit current absorption branch input instruction to the triac.
In particular implementations, the protection switch state acquisition element 100 may not be provided as a separate device. The control element 200 may obtain the on-off state signal or the over-current state signal of each protection switch from the intelligent substation.
The invention has been described above with reference to a few embodiments. However, as is well known to those skilled in the art, other embodiments than the above disclosed invention are equally possible within the scope of the invention, as defined by 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 therein. 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 (9)
1. The short-circuit current absorption branch circuit input control method based on voltage response is characterized by comprising the following steps of:
when the monitored voltage characteristic value of the alternating current bus is detected to be lower than a preset voltage threshold value, generating a short-circuit current absorption branch circuit input instruction; the detecting that the voltage characteristic value of the monitored alternating current bus is lower than a preset voltage threshold value comprises the following steps: in the continuous M detection periods, detecting that the voltage characteristic value of the monitored alternating current bus is lower than a preset voltage threshold value, wherein M is a positive integer;
the short-circuit current absorption branch is a shunt branch which is parallel to the bus and can be controllably thrown into or withdrawn from the power grid;
and responding to the short-circuit current absorption branch input instruction, and controlling the short-circuit current absorption branch to be input into a power grid.
2. The method for controlling input according to claim 1, wherein,
the detecting that the voltage characteristic value of the monitored alternating current bus is lower than a preset voltage threshold value comprises the following steps:
in the continuous M detection periods, the characteristic value of the bus voltage is higher than a preset voltage threshold value;
in the subsequent continuous N detection periods, the characteristic value of the bus voltage is lower than a preset voltage threshold value, wherein N is not smaller than M, M is a positive integer, and N is a positive integer.
3. The input control method according to claim 1, characterized by further comprising:
and generating a short-circuit current absorption branch circuit input instruction when the state of any fault protection switch in all the branches connected in parallel with the bus voltage is overcurrent and when the monitored voltage characteristic value of the alternating current bus is detected to be lower than a preset voltage threshold value.
4. The input control method according to claim 1, characterized by further comprising:
after the short-circuit current absorption branch circuit input instruction is generated, when a preset delay time T2 is reached, a short-circuit current absorption branch circuit exit instruction is generated,
and responding to the short-circuit current absorption branch exit instruction, and controlling the short-circuit current absorption branch to exit from the power grid.
5. The method for controlling input according to claim 1, wherein,
the short-circuit current absorption branch comprises a bidirectional thyristor which is used for controllably connecting or disconnecting with a bus;
and the reactor is connected with the bidirectional thyristor in series and is grounded.
6. A voltage response based short circuit current control apparatus using the voltage response based short circuit current absorption branch input control method according to any one of claims 1 to 5, comprising:
the voltage characteristic value acquisition element is used for detecting the voltage characteristic value of the monitored alternating current bus;
the control component is used for generating a short-circuit current absorption branch circuit input instruction when detecting that the voltage characteristic value of the monitored alternating current bus is lower than a preset voltage threshold value, and the detected voltage characteristic value of the monitored alternating current bus is lower than the preset voltage threshold value, and comprises the following components: in the continuous M detection periods, detecting that the voltage characteristic value of the monitored alternating current bus is lower than a preset voltage threshold value, wherein M is a positive integer;
the command driving element is used for receiving the short-circuit current absorption branch input command and sending the short-circuit current absorption branch input command to the short-circuit current absorption branch so that the short-circuit current absorption branch responds to the short-circuit current absorption branch input command and inputs the short-circuit current absorption branch input command into a power grid.
7. The control device according to claim 6, characterized by further comprising:
the short-circuit current absorption branch is a shunt branch which is parallel to the bus and can be controllably thrown into or withdrawn from the power grid.
8. The control device according to claim 6, characterized by further comprising:
the protection switch state acquisition element is used for receiving and processing an overcurrent signal of the protection switch;
the control element is also used for generating a short-circuit current absorption branch input instruction when the overcurrent state of any fault protection switch in all branches connected in parallel with the bus voltage is overcurrent and when the monitored voltage characteristic value of the alternating current bus is detected to be lower than a preset voltage threshold value.
9. The control device according to claim 6, characterized by further comprising:
a short-circuit current absorption branch comprising a bidirectional thyristor for controllably connecting or disconnecting with a bus;
and the reactor is connected with the bidirectional thyristor in series and is grounded.
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| US5305174A (en) * | 1990-09-03 | 1994-04-19 | Hitachi, Ltd. | Method of and device for protecting electrical power system |
| JP2000078755A (en) * | 1998-09-01 | 2000-03-14 | Nissin Electric Co Ltd | System interlocking apparatus |
| CN102570431A (en) * | 2012-01-10 | 2012-07-11 | 华中电力科学研究院 | Method for limiting short circuit current of power grid |
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| JP2001333537A (en) * | 2000-05-23 | 2001-11-30 | Meidensha Corp | Power supply facility |
| JP2002118950A (en) * | 2000-10-05 | 2002-04-19 | Tokyo Electric Power Co Inc:The | Fault-detecting protective device for rectifier-type current limiting device |
| JP2004166359A (en) * | 2002-11-12 | 2004-06-10 | Mitsubishi Electric Corp | Harmonic restraint circuit |
| WO2014107854A1 (en) * | 2013-01-09 | 2014-07-17 | 宁夏电力公司电力科学研究院 | Power grid current-limiting apparatus, power grid current limiter, and power grid current-limiting system |
| CN110138231A (en) * | 2019-05-10 | 2019-08-16 | 珠海格力电器股份有限公司 | Drive control circuit and its control method, driving control system, air conditioner |
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| US5305174A (en) * | 1990-09-03 | 1994-04-19 | Hitachi, Ltd. | Method of and device for protecting electrical power system |
| JP2000078755A (en) * | 1998-09-01 | 2000-03-14 | Nissin Electric Co Ltd | System interlocking apparatus |
| CN102570431A (en) * | 2012-01-10 | 2012-07-11 | 华中电力科学研究院 | Method for limiting short circuit current of power grid |
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