CN112380682B - Fault current limiter online scheduling control method based on fifth-generation communication system - Google Patents

Fault current limiter online scheduling control method based on fifth-generation communication system Download PDF

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CN112380682B
CN112380682B CN202011211032.8A CN202011211032A CN112380682B CN 112380682 B CN112380682 B CN 112380682B CN 202011211032 A CN202011211032 A CN 202011211032A CN 112380682 B CN112380682 B CN 112380682B
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郭立邦
叶承晋
丁一
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Zhejiang University ZJU
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    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
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Abstract

The invention discloses a fault current limiter online scheduling control method based on a fifth generation communication system. Constructing a fault current limiter on-line scheduling control framework, and generating a fault current limiter scheduling control signal under the condition of short-circuit fault according to the fault current limiter on-line scheduling control framework so as to control the fault current limiter to perform scheduling work; setting time delay, and performing switching scheduling control of a distributed local scheduling control mode and a fault current limiter scheduling control signal by using the time delay; the sensor measures the voltage and current to ground and transmits them to the central transformer substation, and the central transformer substation processes and analyzes them to generate the dispatching control signal of the fault current limiter and transmits it to the fault current limiter to control the turn-off of the bus. The invention can effectively realize the quick suppression of the short-circuit current, simultaneously reduce the scheduling impedance of the fault current limiter, avoid the problem of voltage sag caused by scheduling a large amount of impedance of the fault current limiter and ensure the safe and stable operation of a power grid.

Description

Fault current limiter online scheduling control method based on fifth-generation communication system
Technical Field
The invention relates to a protection device scheduling method in a power system fault scene, in particular to a fault current limiter online scheduling control method based on a fifth generation communication system.
Background
With the continuous expansion of the interconnection scale of the power system and the continuous increase of the quantity of renewable energy sources and thermal power plant grid connection, the amplitude of the short-circuit current in the power system is increasingly remarkable. Taking the east China power grid as an example, the short-circuit current of nearly 30% of 500kV buses is out of limit. The out-of-limit short-circuit current exceeds the maximum cut-off current of an alternating-current circuit breaker installed in the power system, so that the alternating-current circuit breaker cannot be switched in time when short-circuit faults occur, various power equipment is damaged due to overheating under continuous short-circuit current, and cascading faults of the power system and even large power failure of the whole power system are caused. Therefore, for the dispatching department of the power system, it is an urgent task to effectively reduce the short-circuit current when the power system operates.
In recent years, with the development of power electronics technology, fault current limiters have gradually become one of the most effective devices for reducing short-circuit current. The fault current limiter is not switched when the power system normally operates, presents the characteristic of low impedance, and is switched under the condition of detecting the short-circuit current to be immediately converted into a high impedance element, so that the amplitude of the short-circuit current is inhibited, the amplitude is lower than the maximum cut-off current of the alternating-current short-circuit device, and the alternating-current breaker is ensured to cut off the short-circuit current. Although fault current limiters are widely applied to power systems in China, the existing fault current limiter scheduling control model mainly takes a distributed local control model as a main part, namely, switching control is carried out on each fault current limiter according to preset threshold values based on voltage and current information of respective installation positions, and no information interaction exists among the fault current limiters, so that switching of a plurality of fault current limiters is easy to occur when the power system has a short-circuit fault, the switching capacity of the fault current limiters is redundant, further the problems of voltage sag and the like are caused, the electric energy quality is greatly reduced, and the safe and stable operation of the power system is not facilitated.
With the development of communication technology in recent years, an advanced communication technology represented by a fifth generation communication system has the characteristics of high bandwidth, low delay and fast transmission, can well meet the requirement of a fault current limiter for fast response after a short-circuit fault occurs in an electric power system, and how to mount on-line scheduling control of the fault current limiter in the electric power system based on the fifth generation communication system to effectively reduce the short-circuit current during the short-circuit fault and avoid excessive redundancy of the impedance value of the fault current limiter under the scheduling control, thereby reducing the voltage sag of the electric power system and ensuring the electric energy quality is an important content which needs to be researched urgently at present.
Disclosure of Invention
In view of the problems in the background art, the invention provides an online scheduling control method for a fault current limiter based on a fifth generation communication system, which can simply and efficiently obtain an optimal scheduling control mode for the fault current limiter installed in an electric power system when the electric power system has a short-circuit fault, can be used for an electric power system scheduling mechanism to perform effective scheduling control on the fault current limiter when the electric power system actually has a short-circuit fault, and has practical value and significance.
The invention specifically comprises the following steps:
according to the dispatching control characteristics of the fault current limiter and the matching requirements of relay protection equipment of the power system, a fault current limiter online dispatching control framework based on a fifth generation communication system is constructed, and a fault current limiter dispatching control signal is generated according to the fault current limiter online dispatching control framework under the condition of short circuit fault, so that the fault current limiter is controlled to carry out dispatching work;
the invention establishes an optimal dispatching control model of the fault current limiter based on the coupling relation of the dispatching of the fault current limiter to the voltage sag and short-circuit current amplitude limitation; the method particularly takes the minimum sum of the impedance of the fault current limiter under the scheduling control and the voltage sag value caused by the short-circuit fault as an objective function, considers the short-circuit fault current constraint and the voltage sag constraint, realizes the scheduling control of the impedance of the fault current limiter with the minimum sum to enable the short-circuit fault current to meet the requirement of the turn-off of the circuit breaker, and simultaneously reduces the voltage sag caused by the short-circuit fault as much as possible.
Considering the possible faults of the fifth generation communication system, a fault current limiter standby scheduling control mode based on a distributed local scheduling control method is established for classified scheduling: the method comprises the steps that a time delay delta t is preset in a fault current limiter, and when a short-circuit fault is detected, if a fifth generation communication system fails, namely if the fault current limiter does not receive a dispatching control signal of the fault current limiter after the time delay delta t is passed, a distributed local dispatching control mode is started to carry out dispatching control on the fault current limiter; if the fifth generation communication system does not have a fault, namely if the fault current limiter receives the dispatching control signal of the fault current limiter before the time delay delta t, the dispatching control is carried out according to the dispatching control signal of the fault current limiter.
The power system is a multi-terminal direct current transmission system feed-in area. The fifth generation communication system is a 5G system of a fifth generation mobile communication technology.
Specifically, by utilizing the characteristics of low time delay and high reliability of a fifth-generation communication system, a sensor measures the voltage to ground and the current to ground and transmits the voltage to a central substation, a fault current limiter dispatching control signal is generated after the central substation processes and analyzes the voltage and the current to ground, the fault current limiter dispatching control signal is transmitted to a fault current limiter, and the fault current limiter controls the turn-off of a bus, so that the effective matching with a power system relay protection device is realized.
The fault current limiter online scheduling control framework mainly comprises a sensor, a central substation, a fifth generation communication network and a fault current limiter, wherein the sensor is connected to each bus in the power system, the fault current limiter is connected to a line connected with each bus in the power system, and the sensor, the central substation and the fault current limiter are all connected to the fifth generation communication network, so that the sensor and the central substation, and the central substation and the fault current limiter are all connected and communicated through the fifth generation communication network;
measuring the voltage to ground and the current to ground of each bus in the power system by a sensor, wherein the time required for measurement is tM(ii) a The central substation comprises a fault positioning module and a dispatching control module, and transmits and transfers the voltage to earth and the current to earth to the fault positioning module of the central substation through a fifth generation communication network, wherein the time required by transmission and transfer is tC(ii) a Analyzing after a fault positioning module of the central substation receives the voltage to ground and the current to ground, wherein the time required by analysis is tFLDFor the bus i as an example, the judgment is carried out according to the formula:
Figure BDA0002758725710000031
Vi＝V0
wherein, IiAnd ViVoltage to ground and current to ground of the bus I measured for the sensor, IjCurrent injected into bus i for bus j, NBThe total number of the buses is; v0The critical value of the voltage of the bus i to the ground when the short-circuit fault occurs is generally 0 and is represented as V0→0。
If the buses j meet the formula, the fault positioning module judges that the buses j have short-circuit faults, detects and obtains the positions of the buses with the short-circuit faults, and transmits the positions of the buses with the short-circuit faults to the dispatching control module;
according to the position of the short-circuit fault bus, the scheduling control module calls a fault current limiter on-line scheduling control mode corresponding to the short-circuit fault scene at the bus position to generate a fault current limiter scheduling control signal in a short-circuit fault scene off-line scanning mode, and the required working time is tFSDAnd transmitting the dispatching control signal of the fault current limiter to the corresponding fault current limiter through a fifth generation communication network, wherein the time required for transmitting and transmitting is tCFinally, the fault current limiter finishes the actual scheduling control according to the scheduling control signal of the fault current limiter, and the time required by the scheduling control is tF。
The off-line scanning mode of the short-circuit fault scene specifically comprises the following steps:
when the system is offline, analyzing all kinds of potential short-circuit fault scenes in the power system, and simulating the dispatching control of the fault current limiter under each kind of potential short-circuit fault scenes by adopting a fault current limiter optimal dispatching control model to obtain a fault current limiter optimal dispatching control mode set;
when the fault current limiter is on line in real time, according to the position of a short-circuit fault bus, the scheduling control module judges that the actually generated short-circuit fault belongs to the category of a potential short-circuit fault scene, and directly calls an optimal scheduling control variable set corresponding to the short-circuit fault scene from the optimal scheduling control mode set of the fault current limiter as the on-line scheduling control mode of the fault current limiter.
The fault current limiter optimal scheduling control mode set comprises short-circuit faults, short-circuit fault bus positions, an optimal scheduling control variable set and the corresponding relation between the optimal scheduling control variable set and the short-circuit fault bus positions.
The invention considers the time requirement of the on-line optimization of the dispatching control module of the central substation, establishes the short-circuit fault scene off-line scanning mode, so that the dispatching control module of the central substation can judge which short-circuit fault scene the short-circuit fault actually occurs to belong to according to the position of the short-circuit fault bus when the dispatching control module of the central substation actually operates on line, and directly calls the optimal dispatching control mode of the fault current limiter corresponding to the short-circuit fault scene, thereby realizing the on-line dispatching control of the quick response of the fault current limiter.
The optimal scheduling control model of the fault current limiter comprises an objective function and constraint conditions, wherein the objective function is as follows:
Figure BDA0002758725710000041
wherein x isfFor the impedance value of the fault current limiter f, f denoting the serial number of the fault current limiter, vfOptimal scheduling control variable for whether fault current limiter F is scheduled, specifically 0-1 control variable, F is set of all fault current limiters, and Δ VjIs the voltage sag value of the bus j, j represents the serial number of the bus, i is used for the fault bus, j is used for the non-fault bus,
Figure BDA0002758725710000042
is the voltage sag threshold, N, of bus jBThe total number of the buses is; when v isfWhen the current is equal to 0, the fault current limiter f is not scheduled to control the bus connected with the fault current limiter f, and the bus is not limited; when v isfWhen the current is 1, the fault current limiter f is scheduled to control the current limitation of the self-connected bus.
The objective function is the sum of the scheduled impedance value of the fault current limiter and the difference between the bus voltage sag and a preset voltage sag threshold value.
Three-phase simultaneous short-circuit fault occurs to the bus i, and the following constraint conditions are set at the position of the bus with the short-circuit fault:
1) and short-circuit current constraint:
Figure BDA0002758725710000043
wherein, IS,iIs the short-circuit current value of the bus i,
Figure BDA0002758725710000044
and S,iIthe upper limit and the lower limit of the short-circuit current of the bus i are controlled respectively;
Figure BDA00027587257100000410
the voltage value of the bus i before the occurrence of the short-circuit fault,
Figure BDA0002758725710000045
the self-impedance of the bus i before the short-circuit fault occurs; delta ZiiThe self-impedance between the bus i and the bus i after the short-circuit fault is increased due to the dispatching of the fault current limiter;
2) voltage sag constraint:
for the bus j without short-circuit fault, after the bus i has short-circuit fault, the voltage sag value delta VjThe calculation is as follows:
Figure BDA0002758725710000046
wherein the content of the first and second substances,
Figure BDA0002758725710000047
for the mutual impedance, Δ Z, between bus j and bus i before short-circuit failureijThe mutual impedance between the bus i and the bus j after the short-circuit fault is increased due to the scheduling of a fault current limiter; Δ ZiiThe self-impedance increased by the dispatching of a fault current limiter for the bus i after the short-circuit fault;
input fixed short-circuit fault and its bus position
Figure BDA0002758725710000048
S,iI,
Figure BDA0002758725710000049
ΔZijAnd Δ ZiiSolving the optimal scheduling control model of the fault current limiter by adopting a linear programming method for parameters, and calculating to obtain the optimal scheduling control variable v of each fault current limiterfForming an optimal scheduling control variable set of each fault current limiter under the short-circuit fault and the bus position thereof;
and processing different short-circuit faults and bus positions thereof to obtain respective optimal scheduling control variable sets, and forming a fault current limiter optimal scheduling control mode set by the optimal scheduling control variable sets of all the short-circuit faults and the bus positions thereof.
The time delay delta t of the fault current limiter is set to be delta t-tM+tC+tFLD+tFSD+tC。
The distributed local scheduling control mode is to autonomously generate an optimal scheduling control variable v of the fault current limiter f by the following formulaf：
Figure BDA0002758725710000051
Wherein, I1And I0The current values respectively obtained by measuring the fault current limiters after the fault and before the fault, lambda is the critical overcurrent coefficient of the preset fault current limiter, and the current values are used for determining the optimal scheduling control variable v of the fault current limiterf。
In the short-circuit current constraint, a fault current limiter f is arranged between a bus l and a bus k, and the self impedance delta Z increased by the scheduling of the fault current limiter after short-circuit faultiiCalculated from the following equation:
Figure BDA0002758725710000052
wherein, the first and the second end of the pipe are connected with each other,
Figure BDA0002758725710000053
for the impedance on the line connecting bus l and bus k where the fault current limiter f is located,
Figure BDA0002758725710000054
and
Figure BDA0002758725710000055
the self-impedances of bus l and bus k respectively,
Figure BDA0002758725710000056
and
Figure BDA0002758725710000057
for the mutual impedance between the bus i with the short-circuit fault and the bus l and the bus k respectively,
Figure BDA0002758725710000058
is the mutual impedance of bus l and bus k.
In the voltage sag constraint, after short-circuit fault, the mutual impedance delta Z increased by the scheduling of the fault current limiterijCalculated from the following equation:
Figure BDA0002758725710000059
wherein the content of the first and second substances,
Figure BDA00027587257100000510
and
Figure BDA00027587257100000511
respectively are the mutual impedance between the bus j and the bus l and the bus k respectively;
voltage sag threshold for bus j
Figure BDA00027587257100000512
According to the following settings:
if the bus j is only connected with the AC bus, the bus is a pure AC bus, and the voltage sag threshold value is
Figure BDA00027587257100000513
Freely selecting according to the bus requirements;
if the bus j is also connected with the DC bus, the bus is an AC/DC coupling bus, and the voltage sag threshold value
Figure BDA00027587257100000514
If it is necessary to ensure that the converter m on the dc bus connected to the bus j can work normally, the voltage sag threshold value
Figure BDA00027587257100000515
The method comprises the following steps:
Figure BDA00027587257100000516
wherein the content of the first and second substances,
Figure BDA00027587257100000517
is the voltage of the bus j before failure, nmIs the conversion ratio of converter m, Im,DCFor rated direct current flowing through the inverter m, XmIs an equivalent commutation reactance, theta, of the inverter mmIs the commutation control angle of the inverter m,
Figure BDA0002758725710000061
the minimum off angle of the inverter m is generally set to 7 °.
According to the dispatching control characteristics of the fault current limiter and the matching requirements of other relay protection devices, the invention establishes a fault current limiter online dispatching control framework based on a fifth-generation communication system, and sets a distributed local control method as a standby dispatching control mode in the framework aiming at possible faults of the communication system. Meanwhile, an optimal scheduling control model of the fault current limiter is established, and an off-line scanning mode of a short-circuit fault scene is introduced into the model, so that all short-circuit faults of the power system can be scanned in advance by an off-line method to obtain a corresponding optimal scheduling control mode of the fault current limiter, and the power system scheduling mechanism can timely and effectively call the corresponding scheduling control mode of the fault current limiter according to the identified short-circuit fault scene when the power system runs in real time, thereby realizing the fast and efficient scheduling control of the fault current limiter.
The invention has the beneficial effects that:
the method combines the characteristics of high bandwidth, low delay and fast transmission of a fifth generation communication system, the established fault current limiter online scheduling control framework can ensure the effective switching of the fault current limiter during short-circuit fault, and the distributed local control method is called during communication system fault, so that the fault current limiter can be ensured to be switched in time according to the distributed local control method during communication system fault, and the method can be effectively and reliably used during communication system fault.
In addition, the fault current limiter online scheduling control model established by the method can effectively reduce the scheduling control impedance of the fault current limiter during short-circuit fault, and avoid voltage sag caused by redundant scheduling of the fault current limiter during short-circuit fault, so that the power quality of the power system is ensured while the requirement on short-circuit current suppression of the power system is met by using the minimum scheduling control impedance of the fault current limiter.
Therefore, the invention carries out online scheduling control on the fault current limiter by the ground voltage and the ground current of each bus of the power system under the condition of short-circuit fault, can effectively realize quick suppression on the short-circuit current, further reduces the scheduling impedance of the fault current limiter, avoids the problem of voltage sag caused by scheduling a large amount of impedance of the fault current limiter, and ensures the safe and stable operation of a power grid.
Drawings
Fig. 1 is a diagram of an on-line scheduling control framework of a fault current limiter based on a fifth generation communication system of the present invention;
FIG. 2 is a schematic diagram of an offline scanning mode for a short-circuit fault scenario according to the present invention;
FIG. 3 is a schematic diagram of the backup scheduling control mode timing engagement in a communication system failure scenario according to the present invention;
FIG. 4 is a 39-node AC/DC system topology for simulation according to the present invention;
FIG. 5 is a schematic diagram illustrating simulation of online scheduling control results of a fault current limiter according to the present invention;
fig. 6 is a schematic diagram illustrating the effect of the scheduling control result of the fault current limiter of the present invention on the short-circuit fault current.
Detailed Description
The following is a further description with reference to the examples and the accompanying drawings.
The examples of the complete method according to the invention are as follows:
1. fault current limiter online scheduling control framework based on fifth generation communication system
As shown in fig. 1, the fault current limiter online scheduling control framework based on the fifth generation communication system in the invention mainly comprises a sensor, a central substation, a fifth generation communication network and a fault current limiter. The sensors are connected to all buses in the power system, the fault current limiters are connected to lines connected with all the buses in the power system, and the sensors, the central substation and the fault current limiters are all connected to a fifth-generation communication network, so that the sensors and the central substation, and the central substation and the fault current limiters are all connected and communicated through the fifth-generation communication network.
If the power system fed in by the multi-terminal direct-current power transmission system is taken as a research object, firstly, the voltage to ground and the current to ground of each bus of the power system fed in by the multi-terminal direct-current power transmission system are measured by a sensor, and the measurement time is tM。
Next, the sensor transmits the measured ground voltage and ground current to the central substation over a fifth generation communication network for a transmission time tC。
After the central substation receives the voltage to ground and the current to ground measurement values, analysis is carried out based on a fault positioning module, and the analysis time is tFLDTaking the bus i as an example, the analysis formula of the fault location module is as follows:
Figure BDA0002758725710000071
Vg＝V0
wherein, IiAnd ViVoltage to ground and current to ground of the bus I measured for the sensor, IjCurrent injected into bus i for bus j, NBThe total number of the buses is; v0The critical value of the voltage of the bus i to the ground when the short-circuit fault occurs is generally 0 and is represented as V0→0。
If the buses i all meet the formula, the fault positioning module judges that the bus j has a short-circuit fault, detects and obtains the position of the bus with the short-circuit fault, and transmits the position of the bus with the short-circuit fault to the dispatching control module;
according to the position of the short-circuit fault bus, the scheduling control module uses a short-circuit fault scene off-line scanning mode to call a fault current limiter on-line scheduling control mode corresponding to the scene of the short-circuit fault at the bus position to generate a fault current limiter scheduling control signal, and the required working time is tFSDAnd transmitting the dispatching control signal of the fault current limiter to the corresponding fault current limiter through a fifth generation communication network, wherein the time required for transmitting and transmitting is tCFinally, the fault current limiter finishes the actual scheduling control according to the scheduling control signal of the fault current limiter, and the time required by the scheduling control is tF。
2. Short-circuit fault scene off-line scanning mode
As shown in fig. 2, when the system is offline, all potential short-circuit fault scenarios in the power system fed by the multi-terminal dc power transmission system are analyzed, and each potential short-circuit fault scenario is simulated by using the fault current limiter optimal scheduling control model, so as to form a fault current limiter optimal scheduling control mode set.
When the system runs online, according to the position of the short-circuit fault bus, the scheduling control module judges which scene of the offline acquired optimal scheduling control mode set of the fault current limiter the short-circuit fault actually occurs in, and directly calls the scheduling control mode of the fault current limiter corresponding to the scene to form a scheduling control signal result of the fault current limiter.
The objective function of the optimal scheduling control model of the fault current limiter is as follows:
Figure BDA0002758725710000081
three-phase simultaneous short-circuit fault occurs to the bus i, and the following constraint conditions are set at the position of the bus with the short-circuit fault:
1) and (3) short-circuit current constraint:
Figure BDA0002758725710000082
Figure BDA0002758725710000083
2) voltage sag constraint:
Figure BDA0002758725710000084
Figure BDA0002758725710000085
voltage sag threshold for bus j
Figure BDA0002758725710000086
According to the following settings:
if the bus j is only connected with the AC bus, the bus is a pure AC bus, and the voltage sag threshold value is
Figure BDA0002758725710000087
Freely selecting according to the bus requirements;
if the bus j is also connected with the DC bus, the bus is an AC/DC coupling bus, and the voltage sag threshold value
Figure BDA0002758725710000088
If it is necessary to ensure that the converter m on the dc bus connected to the bus j can work normally, the voltage sag threshold value
Figure BDA0002758725710000089
The method comprises the following steps:
Figure BDA00027587257100000810
input fixed short-circuit fault and its bus position
Figure BDA00027587257100000811
S,iI,
Figure BDA00027587257100000812
ΔZijAnd Δ ZiiSolving the optimal scheduling control model of the fault current limiter by adopting a linear programming method, and calculating to obtain the optimal scheduling control variable v of each fault current limiterfForming an optimal scheduling control variable set under the short-circuit fault and the bus position thereof;
and processing different short-circuit faults and bus positions thereof to obtain respective optimal scheduling control variable sets, and forming a fault current limiter optimal scheduling control mode set by the optimal scheduling control variable sets of all the short-circuit faults and the bus positions thereof.
3. Standby scheduling control mode in communication system fault scene
If the fifth generation communication system fails, as shown in fig. 3, a standby scheduling control mode of the fault current limiter based on a distributed local scheduling control method is established for classified scheduling: a time delay delta t is preset for the fault current limiter, and the time delay delta t is set to be delta t-tM+tC+tFLD+tFSD+tC。
When a short-circuit fault is detected, if a fifth generation communication system fails, namely if the fault current limiter does not receive a dispatching control signal of the fault current limiter after time delay delta t, a distributed local dispatching control mode is started to carry out dispatching control on the fault current limiter, specifically, an optimal dispatching control variable v of the fault current limiter f is autonomously generated through the following formulaf：
Figure BDA0002758725710000091
If the fifth generation communication system does not have a fault, namely if the fault current limiter receives the dispatching control signal of the fault current limiter before the time delay delta t, the dispatching control is carried out according to the dispatching control signal of the fault current limiter.
4. Case simulation
As shown in fig. 4, case simulation is performed by taking a power system fed by a three-terminal dc power transmission system including 39 nodes as an example. Assuming that the circuit breaker cannot be turned off when the bus current exceeds 20p.u. and short-circuit fault current needs to be reduced through the scheduling of the fault current limiter for turning off, a total of 7 buses meet the requirements. Regarding the short-circuit faults of the 7 buses as independent events, the 7 short-circuit fault scenarios are equivalent, as shown in table 1. Assume that 5 fault current limiters are installed in a region, and the impedance and installation position of each fault current limiter are shown in table 2.
TABLE 1
Figure BDA0002758725710000092
Figure BDA0002758725710000101
TABLE 2
Figure BDA0002758725710000102
The results of the fault current limiter scheduling control generated by the fault current limiter online scheduling control model based on the fifth generation communication system provided by the invention under different scenes are shown in fig. 5, and it can be seen that under the scene of short circuit fault in different fields, except that the results of the fault current limiter scheduling control in the scene 1 and the scene 5 are the same, the results of the fault current limiter scheduling control in other scenes are different, and the fault current limiter online scheduling control model based on the fifth generation communication system provided by the invention can effectively form an optimal fault current limiter scheduling control scheme aiming at different short circuit fault positions and short circuit fault currents under different scenes.
The short-circuit fault current generated after the fault current limiter scheduling control scheme obtained by the fault current limiter online scheduling control model based on the fifth generation communication system provided by the invention in each short-circuit fault scene is compared with the short-circuit fault current in each short-circuit fault scene without the fault current limiter, as shown in fig. 6. Therefore, the fault current limiter scheduling control scheme formed by the fault current limiter online scheduling control model based on the fifth generation communication system can effectively control the short-circuit current in each short-circuit fault scene to be within the preset upper and lower limit ranges, and ensure that the power system can still normally complete the circuit breaker shutdown under the condition of short-circuit fault.
The voltage sag out-of-limit condition formed after the fault current limiter scheduling control scheme obtained by the fault current limiter online scheduling control model based on the fifth generation communication system provided by the invention under each short-circuit fault scene is compared with the voltage sag out-of-limit condition of each short-circuit fault scene formed by the scheduling control by adopting the distributed local control method, as shown in table 3.
TABLE 3
Figure BDA0002758725710000111
The technical scheme provided by the invention can effectively reduce the number of buses with voltage sag exceeding the preset voltage sag threshold value in each short-circuit fault scene, and ensure the voltage stability of the power system under the condition of short-circuit fault.

Claims (5)

1. A fault current limiter online scheduling control method based on a fifth generation communication system is characterized by comprising the following steps:
according to the dispatching control characteristics of the fault current limiter and the matching requirements of relay protection equipment of the power system, a fault current limiter online dispatching control framework based on a fifth generation communication system is constructed, and a fault current limiter dispatching control signal is generated according to the fault current limiter online dispatching control framework under the condition of short-circuit fault, so that the fault current limiter is controlled to carry out dispatching work;
meanwhile, a fault current limiter standby scheduling control mode based on a distributed local scheduling control method is established for classified scheduling: the method comprises the steps that a time delay delta t is preset in a fault current limiter, and after a short-circuit fault is detected, if the fault current limiter does not receive a dispatching control signal of the fault current limiter after the time delay delta t passes, a distributed local dispatching control mode is started to carry out dispatching control on the fault current limiter; if the fault current limiter receives the dispatching control signal of the fault current limiter before the time delay delta t, carrying out dispatching control according to the dispatching control signal of the fault current limiter;
the fault current limiter online scheduling control framework mainly comprises a sensor, a central substation, a fifth generation communication network and a fault current limiter, wherein the sensor is connected to each bus in the power system, the fault current limiter is connected to a line connected with each bus in the power system, and the sensor, the central substation and the fault current limiter are all connected to the fifth generation communication network, so that the sensor and the central substation, and the central substation and the fault current limiter are all connected and communicated through the fifth generation communication network;
measuring the voltage to ground and the current to ground of each bus in the power system by a sensor, wherein the time required for measurement is tM(ii) a The central substation comprises a fault positioning module and a scheduling control module, and transmits and transfers the voltage to earth and the current to earth to the fault positioning module of the central substation through a fifth generation communication network, wherein the time required by transmission and transfer is tC(ii) a Analyzing after a fault positioning module of the central substation receives the voltage to ground and the current to ground, wherein the time required by analysis is tFLDFor the bus i as an example, the judgment is carried out according to the formula:
Figure FDA0003597939240000011
Vi＝V0
wherein, IiAnd ViVoltage to ground and current to ground of the bus I measured for the sensor, IjCurrent injected into bus i for bus j, NBThe total number of the buses is; v0The voltage is a critical value of the voltage of the bus i to the ground when the short-circuit fault occurs;
if the buses j meet the formula, the fault positioning module judges that the buses j have short-circuit faults, detects and obtains the positions of the buses with the short-circuit faults, and transmits the positions of the buses with the short-circuit faults to the dispatching control module;
according to the position of the short-circuit fault bus, the scheduling control module calls a fault current limiter on-line scheduling control mode corresponding to the short-circuit fault scene at the bus position to generate a fault current limiter scheduling control signal in a short-circuit fault scene off-line scanning mode, and the required working time is tFSDAnd transmitting the dispatching control signal of the fault current limiter to the corresponding fault current limiter through a fifth generation communication network, wherein the time required for transmitting and transmitting is tCFinally, the fault current limiter finishes the actual scheduling control according to the scheduling control signal of the fault current limiter, and the time required by the scheduling control is tF；
The off-line scanning mode of the short-circuit fault scene specifically comprises the following steps:
when the system is offline, analyzing all kinds of potential short-circuit fault scenes in the power system, and simulating the dispatching control of the fault current limiter under each kind of potential short-circuit fault scenes by adopting a fault current limiter optimal dispatching control model to obtain a fault current limiter optimal dispatching control mode set;
when the fault current limiter is on line in real time, according to the position of a short-circuit fault bus, the scheduling control module judges that the actually generated short-circuit fault belongs to the category of a potential short-circuit fault scene, and directly calls an optimal scheduling control variable set corresponding to the short-circuit fault scene from the optimal scheduling control mode set of the fault current limiter as the on-line scheduling control mode of the fault current limiter;
the optimal scheduling control model of the fault current limiter comprises an objective function and constraint conditions, wherein the objective function is as follows:
Figure FDA0003597939240000021
wherein x isfFor the impedance value of the fault current limiter f, f denoting the serial number of the fault current limiter, vfOptimal scheduling control variable for whether fault current limiter F is scheduled, specifically 0-1 control variable, F is set of all fault current limiters, and Δ VjIs the voltage sag value of the bus j, j represents the serial number of the bus,
Figure FDA0003597939240000022
is the voltage sag threshold, N, of the bus jBThe total number of the buses is;
setting the following constraint conditions at the position of the bus with the short-circuit fault:
1) and (3) short-circuit current constraint:
Figure FDA0003597939240000023
wherein, IS,iIs the short-circuit current value of the bus i,
Figure FDA0003597939240000024
and S,iIthe upper limit and the lower limit of the short-circuit current of the bus i are controlled respectively; vi 0The voltage value of the bus i before the occurrence of the short-circuit fault,
Figure FDA0003597939240000025
the self-impedance of the bus i before the short-circuit fault occurs; delta ZiiThe self-impedance between the bus i and the bus i after the short-circuit fault is increased due to the dispatching of the fault current limiter;
2) voltage sag constraint:
for the bus j without short-circuit fault, after the bus i has short-circuit fault, the voltage sag value delta VjThe calculation is as follows:
Figure FDA0003597939240000026
wherein the content of the first and second substances,
Figure FDA0003597939240000031
for the mutual impedance, Δ Z, between bus j and bus i before short-circuit failureijThe mutual impedance between the bus i and the bus j after the short-circuit fault is increased due to the scheduling of a fault current limiter; delta ZiiIs shortThe self-impedance of the bus i after the circuit fault is increased due to the scheduling of the fault current limiter;
input fixed short-circuit fault and its bus position
Figure FDA0003597939240000032
And Δ ZiiThe optimal scheduling control model of the fault current limiter is solved through parameters, and the optimal scheduling control variable v of each fault current limiter is obtained through calculationfForming an optimal scheduling control variable set of each fault current limiter under the short-circuit fault and the bus position thereof;
and processing different short-circuit faults and bus positions thereof to obtain respective optimal scheduling control variable sets, and forming a fault current limiter optimal scheduling control mode set by the optimal scheduling control variable sets of all the short-circuit faults and the bus positions thereof.
2. The fault current limiter online scheduling control method based on the fifth generation communication system as claimed in claim 1, wherein: the time delay delta t of the fault current limiter is set to be delta t-tM+tC+tFLD+tFSD+tCThe distributed local dispatching control mode is to generate the optimal dispatching control variable v of the fault current limiter f autonomously through the following formulaf：
Figure FDA0003597939240000033
Wherein, I1And I0The current values are respectively measured by the fault current limiter after the fault and the fault current limiter before the fault, and lambda is a preset critical overcurrent coefficient of the fault current limiter.
3. The fault current limiter online scheduling control method based on the fifth generation communication system as claimed in claim 1, wherein: in the short-circuit current constraint, a fault current limiter f is arranged between a bus l and a bus k, and the self-resistance increased due to the scheduling of the fault current limiter after short-circuit faultanti-Delta ZiiCalculated from the following equation:
Figure FDA0003597939240000034
wherein the content of the first and second substances,
Figure FDA0003597939240000035
for the impedance on the line connecting bus l and bus k where the fault current limiter f is located,
Figure FDA0003597939240000036
and
Figure FDA0003597939240000037
the self-impedances of bus l and bus k respectively,
Figure FDA0003597939240000038
and
Figure FDA0003597939240000039
for the mutual impedance between the bus i with the short-circuit fault and the bus l and the bus k respectively,
Figure FDA00035979392400000310
is the mutual impedance of bus l and bus k.
4. The fault current limiter online scheduling control method based on the fifth generation communication system as claimed in claim 1, wherein: in the voltage sag constraint, after short-circuit fault, the mutual impedance delta Z increased by the scheduling of the fault current limiterijCalculated from the following equation:
Figure FDA00035979392400000311
wherein, the first and the second end of the pipe are connected with each other,
Figure FDA00035979392400000312
and
Figure FDA00035979392400000313
respectively, the mutual impedance between the bus j and the bus l, the bus k, respectively.
5. The fault current limiter online scheduling control method based on the fifth generation communication system as claimed in claim 1, wherein: voltage sag threshold for bus j
Figure FDA0003597939240000041
According to the following settings:
if the bus j is only connected with the AC bus, the bus is a pure AC bus, and the voltage sag threshold value is
Figure FDA0003597939240000042
Freely selecting according to the bus requirements;
if the bus j is also connected with the DC bus, the bus is an AC/DC coupling bus, and the voltage sag threshold value
Figure FDA0003597939240000043
If it is required to ensure that the converter m on the dc bus connected to the bus j can work normally, the voltage sag threshold value
Figure FDA0003597939240000044
The method comprises the following steps:
Figure FDA0003597939240000045
wherein the content of the first and second substances,
Figure FDA0003597939240000046
is the voltage of the bus j before failure, nmIs the conversion ratio of converter m, Im,DCRated for current through inverter mDirect current, XmIs an equivalent commutation reactance, theta, of the inverter mmIs the commutation control angle of the inverter m,
Figure FDA0003597939240000047
is the minimum off angle of the inverter m.
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