CN110401208B - Intelligent setting method for high-frequency cutting machine of AC/DC system - Google Patents
Intelligent setting method for high-frequency cutting machine of AC/DC system Download PDFInfo
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/04—Circuit arrangements for ac mains or ac distribution networks for connecting networks of the same frequency but supplied from different sources
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/24—Arrangements for preventing or reducing oscillations of power in networks
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/36—Arrangements for transfer of electric power between ac networks via a high-tension dc link
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
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Abstract
The intelligent setting method of the AC/DC system high-frequency cutting machine is a real-time online changeable scheme, the optimal cutting machine combination under the condition can be given to different faults, compared with the traditional solving method aiming at specific operation modes and fault setting, the intelligent setting method is poor in adaptability under certain faults and modes, the problem that the cutting machine capacity is too much or too little exists is solved, the capacity of a cutting machine set can be intelligently determined according to the actual line fault condition, the relation between different fault types and the output of a generator is reflected through load flow reverse tracking, the problems that the traditional scheme cannot adapt to various fault types are solved, the cutting machine capacity is relatively conservative, the cutting is too much and the like are solved, and the applicability of various operation modes such as enlargement, enlargement and the like is remarkably improved.
Description
Technical Field
The application relates to the technical field of high-frequency cutting machines in the safe and stable operation process of an electric power system, in particular to an intelligent setting method of an alternating-current and direct-current system high-frequency cutting machine.
Background
The frequency of the power system is closely related to the active power, and the frequency change is influenced by the output adjustment of the generator, the fluctuation of the load power and other aspects. When the active power provided by the power supply is larger than the load power, the system power is excessive, the frequency is increased, and when the active power provided by the power supply is smaller than the load power, the system power is insufficient, and the frequency is reduced. Because of the moment change of load power and the uncertainty of the output of the current large-scale connected new energy power generation devices such as wind power, photovoltaic and the like, the power of the whole power system is in real-time dynamic balance. In normal operation, although the system frequency fluctuates, the system frequency is not changed greatly and is always stable at about 50 Hz.
Frequency stabilization is a precondition for stable operation of the power system. After a large-scale direct current transmission project is put into operation successively, the current power grid shows a tendency of asynchronous interconnection. At this time, if the dc line fails, a large power remains, which causes a series of frequency problems. When the system frequency is detected to be higher than the allowable frequency, the high-frequency cutting machine device serving as a stabilizing measure cuts off part of the power supply unit immediately after short delay, so that the whole system frequency is restored to the power frequency again.
Parameters to be set for the high-frequency cutting scheme are as follows: cutting machine times, action frequency, time delay, cutting machine quantity of each round and cutting machine objects. The quality of a high-frequency cutting scheme mainly depends on the cutting amount and the selection of the cutting objects in each round, but for the determination of the cutting amount and the cutting objects in each round, the traditional scheme is limited to a specific historical background, and has the following problems:
(1) The traditional scheme determines the cutting quantity and the cutting object of each round according to the imaginary maximum power surplus and the running experience, lacks a certain theoretical basis, and does not consider the connection of faults and the output of a generator and the transient characteristics of an actual power grid.
(2) The traditional scheme has huge cutter objects and thousands of combinations exist, the cutter quantity and cutter objects of each round are mainly determined according to certain specific operation modes, the flexibility is poor, and under other operation modes, the scheme is not suitable.
(3) Because the cutting machine quantity and the cutting machine object of each round in the traditional scheme are not the combination of the cutting machines in the optimal sense, the excessive cutting capacity and the insufficient cutting capacity of the machine set are easily caused.
Therefore, if the capacity of the cutting unit and the cutting object can be flexibly determined according to the actual running mode of the power grid and the fault line condition, the cutting amount is minimum on the premise of ensuring that the system frequency is recovered to be in a normal range, namely, the minimum cutting principle is met, and the requirement of large-scale pure direct current interconnection between the areas is met.
Disclosure of Invention
The intelligent setting method of the high-frequency cutting machine of the AC/DC system solves the problems that in a traditional solving method, the cutting machine capacity is too high or too low due to the fact that the traditional solving method is formulated for specific operation modes and faults, adaptation is poor under certain faults and modes, compared with the existing analyzing method, the method can flexibly determine the cutting machine set capacity and the cutting machine object according to the actual operation modes and fault line conditions of a power grid, the cutting machine capacity is minimum on the premise that the system frequency is restored to be within a normal range, namely the minimum cutting machine principle is met, and the requirement of large-scale pure DC interconnection between areas is met.
The technical scheme adopted for solving the technical problems is as follows:
an intelligent setting method of an alternating current-direct current system high-frequency cutting machine comprises the following steps:
calculating the power flow contribution degree of each power unit node of the power plant after line faults by using a power flow back tracking technology;
sequencing the power flow contribution degrees of the power supply unit nodes according to the values of the power flow contribution degrees from large to small;
selecting the median of the tide contribution degree value as a reference value, and optimizing the proportion of the cutting machine;
generating cutting machine quantity of each unit of each round according to the cutting machine proportion, accumulating the cutting machine quantity to obtain accumulated power and checking the accumulated power, and if the accumulated power is larger than the maximum cutting machine quantity P of the round max Limiting the cutting amount to the maximum cutting amount, if the accumulated power is smaller than the maximum cutting amount P of the wheel max Checking, namely setting the rotary cutting machine object to the unit just by checking;
judging whether the steady-state frequency of the system after cutting meets the steady-state frequency requirement, if so, finishing the setting, otherwise, repeating the operation until the steady-state frequency of the system after cutting meets the steady-state frequency requirement.
Optionally, the step of calculating the power flow contribution degree of each power plant power supply unit node after the line fault by using the power flow inverse tracking technology further comprises the steps of,
preprocessing an external line of a local regional power grid, and determining the maximum cutting machine capacity P of each round max 。
Optionally, the determining of the maximum cutter capacity per round P max Comprising:
firstly, disconnecting an outgoing line of a regional power grid, simulating island operation of the regional power grid, and enabling the system frequency to just reach a first-round low-frequency load shedding action value in a mode of gradually increasing the cutting capacity of the regional power grid, wherein the cutting capacity is the maximum cutting capacity P of each round max 。
Optionally, the calculating the power flow contribution degree of each power plant power supply unit node after the line fault by using a power flow inverse tracking technology includes:
when the system operates normally, the transmission power from the node i to the adjacent node q is P iq If the i-q line fails, the system will have surplus power P which can not be sent out iq ：
Wherein P is i For the inflow power of node i, P Gk For the power of the generator on the node k, A is a tide inverse tracking coefficient matrix, and an element a in the matrix A ij The method meets the following conditions:
wherein P is j For the inflow power of node j, P ji For node j to transmit power to adjacent node i via line, D i For all the node sets of which the power flows to and is connected with the node i, the power flow contribution degree of the kth generator node of the fault line is as follows:
wherein PFC is provided k And contributing to the tide of the kth generator node.
Optionally, the sorting the power flow contribution degrees of the power unit nodes according to the values of the power flow contribution degrees from large to small further includes:
after the power flow contribution degree of each power supply node is calculated, firstly sorting is carried out according to the power flow contribution degree, and then the power supply nodes are divided into 3 groups with extremely high relevance [ a,1], relevance [ b, a) and relatively low relevance [0, b) according to step length, wherein a=0.2 and b=0.1.
Optionally, selecting the median of the power flow contribution degree value as a reference value, and performing the optimization of the cutting machine proportion, including:
firstly, generating the capacity of each round of cutting machine according to the running condition of a local power grid, and determining an initial proportion c according to the ratio of the capacity of each round of cutting machine to the total capacity, wherein the initial proportion is 3% -5%;
then selecting the median of the power flow contribution degree value sequences of the power supply units after the sequencing as a reference value of the power flow contribution degree;
finally, comparing the power flow contribution degree of each power supply node with a reference value: if the trend contribution degree is larger than the reference value, the unit cutting proportion can be properly increased by multiplying the ratio of the trend contribution degree to the reference value; if the power flow contribution degree is smaller than the reference value, the cutting machine proportion is defined as the initial proportion c), namely:
wherein PFC is the power flow contribution degree, PFC ref Is a reference value.
Optionally, the generating the cutting machine quantity of each unit according to the cutting machine proportion, and accumulating the cutting machine quantity includes:
and according to the cutting ratio, multiplying the actual installed capacity of the power plant by the cutting ratio to generate the cutting quantity of each unit of each round, and accumulating the cutting quantity.
Optionally, the step of judging whether the steady-state frequency of the system after cutting meets the steady-state frequency requirement, if yes, finishing the setting, otherwise, repeating the operation until the steady-state frequency of the system after cutting meets the steady-state frequency requirement, wherein the steady-state frequency requirement range of the system after cutting is 49.8-50.2Hz.
The technical scheme provided by the application comprises the following beneficial technical effects:
according to the intelligent setting method for the AC/DC system high-frequency cutting machine, firstly, the power flow contribution degree of each power plant power supply unit node after line faults is calculated through a power flow reverse tracking technology, the power flow contribution degree is sorted and grouped according to the value of the power flow contribution degree from large to small, the unit with the highest power flow contribution degree of the line faults is found, the unit is cut off preferentially, and the power flow contribution degree is ensured theoreticallyThe capacity of the cutting machine is optimal; secondly, selecting the median of the tide contribution degree values of the power plants which are sorted and grouped as a reference value, and optimizing the proportion of the cutting machine; finally, after optimizing the cutting machine proportion, accumulating the cutting machine quantity of each unit of each round to obtain accumulated power and checking the accumulated power, and if the accumulated power is larger than the maximum cutting machine quantity P of the round max Limiting the cutting amount to the maximum cutting amount, if the accumulated power is smaller than the maximum cutting amount P of the wheel max And checking to determine whether the cutting machine is set by the round cutting machine object until the cutting machine is set, and judging whether the steady-state frequency of the system after the cutting machine meets the steady-state frequency requirement after the cutting machine is finished, so as to finally determine whether the setting is finished. The scheme is a real-time online changeable scheme, the optimal cutter combination under the condition can be given to different faults, compared with the traditional solving method aiming at specific operation modes and fault formulation, the method is poor in adaptation under certain faults and modes, and the problems of excessive or insufficient cutter capacity exist.
Drawings
In order to more clearly illustrate the technical solutions of the present application, the drawings that are needed in the embodiments will be briefly described below, and it will be obvious to those skilled in the art that other drawings can be obtained from these drawings without inventive effort.
Fig. 1 is a main flow diagram of an intelligent setting method of an ac/dc system high-frequency cutting machine according to an embodiment of the present application;
fig. 2 is a flowchart of an intelligent setting method of an ac/dc system high-frequency cutting machine according to an embodiment of the present application;
fig. 3 is an electrical wiring diagram of a 3-power plant 10-node ac/dc system according to an embodiment of the present application;
FIG. 4 is a graph of system frequency variation for determining maximum cut capacity per round provided by an embodiment of the present application;
FIG. 5 is a graph comparing the frequency change of a system according to the embodiment of the present application with the frequency change of a system without any measures;
fig. 6 is a partial enlarged view of the system frequency provided by the embodiment of the present application, taken with and without any action.
Detailed Description
In order to enable those skilled in the art to better understand the technical solutions in the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application; it will be apparent that the described embodiments are only some, but not all, of the embodiments of the present application. All other embodiments, which can be made by one of ordinary skill in the art based on the embodiments herein without making any inventive effort, shall fall within the scope of the present application.
Referring to fig. 1, the main flow diagram of an intelligent setting method of an ac/dc system high-frequency cutting machine provided in an embodiment of the present application is shown, and the method includes the following steps:
s1: and (3) calculating the power flow contribution degree of each power unit node of the power plant after the line fault by using a power flow reverse tracking technology.
The power flow contribution degree PFC range is between 0 and 1, the proportion of the injection power of different generator nodes in the power flow of the line is measured, when the PFC of a certain generator node is larger, the power flow contribution degree of the generator to the line is larger and the generator should be cut off.
S2: and sequencing the power flow contribution degrees of the power supply unit nodes according to the values of the power flow contribution degrees from large to small.
In actual operation, a situation that a plurality of power supply nodes PFC are similar may occur, and if the power supply nodes PFC are cut off successively according to the size of the PFC, the complexity of cutting machine is increased, so that the cutting machine process can be simplified by adopting a sequencing method.
S3: and selecting the median of the tide contribution degree value as a reference value, and optimizing the proportion of the cutting machine.
The larger PFC of the power supply node indicates that the larger the association degree of the power supply node and the surplus power is, the larger the capacity to be cut is, so that the cutting speed of the unit is further improved by adopting a method for optimizing the proportion of the capacity of each round of cutting machine to the total capacity of the unit, and the system frequency is effectively restrained from being continuously increased and is quickened to recover.
S4: generating cutting machine quantity of each unit of each round according to the cutting machine proportion, accumulating the cutting machine quantity to obtain accumulated power and checking the accumulated power, and if the accumulated power is larger than the maximum cutting machine quantity P of the round max Limiting the cutting amount to the maximum cutting capacity, if the accumulated power is smaller than the maximum cutting amount P of the wheel max And checking to just set the rotary cutter object to the machine set.
S5: judging whether the steady-state frequency of the system after cutting meets the steady-state frequency requirement, if so, finishing the setting, otherwise, repeating the operation until the steady-state frequency of the system after cutting meets the steady-state frequency requirement.
The embodiment of the application provides a real-time online changeable scheme, which can give the optimal cutter combination under the condition to different faults, compared with the traditional solving method aiming at specific operation modes and fault formulation, the method is poor in adaptation under certain faults and modes, and has the problem that the cutter capacity is too much or too little.
Optionally, the step of calculating the power flow contribution degree of each power plant power supply unit node after the line fault by using the power flow inverse tracking technology further comprises the steps of,
preprocessing an external line of a local regional power grid, and determining the maximum cutting machine capacity P of each round max 。
Optionally, the determining of the maximum cutter capacity per round P max Comprising:
firstly, disconnecting an outgoing line of a regional power grid, simulating island operation of the regional power grid, and enabling the system frequency to just reach a first-round low-frequency load shedding action value in a mode of gradually increasing the cutting capacity of the regional power grid, wherein the cutting capacity is the maximum cutting capacity P of each round max 。
To determine maximum cutter capacity per round P max Firstly, the outgoing line of the regional power grid can be manually disconnected, so that the island operation of the regional power grid is simulated, in this case, the cutting capacity of the regional power grid is gradually increased, so that the system frequency just reaches the action value of the first-round low-frequency load shedding, and the cutting capacity is the maximum cutting capacity P of each round max 。
Optionally, the calculating the power flow contribution degree of each power plant power supply unit node after the line fault by using a power flow inverse tracking technology includes:
when the system operates normally, the transmission power from the node i to the adjacent node q is P iq If the i-q line fails, the system will have surplus power P which can not be sent out iq ：
Wherein P is i For the inflow power of node i, P Gk For the power of the generator on the node k, A is a tide inverse tracking coefficient matrix, and an element a in the matrix A ij The method meets the following conditions:
wherein P is j For the inflow power of node j, P ji For node j to be routed to the adjacent nodeThe power of delivery at point i, D i For all the node sets of which the power flows to and is connected with the node i, the power flow contribution degree of the kth generator node of the fault line is as follows:
wherein PFC is provided k And contributing to the tide of the kth generator node.
Optionally, the sorting the power flow contribution degrees of the power unit nodes according to the values of the power flow contribution degrees from large to small further includes:
after the power flow contribution degree of each power supply node is calculated, firstly sorting is carried out according to the power flow contribution degree, and then the power supply nodes are divided into 3 groups with extremely high relevance [ a,1], relevance [ b, a) and relatively low relevance [0, b) according to step length, wherein a=0.2 and b=0.1.
And sorting and grouping according to the value of the power flow contribution degree from large to small, finding out a unit with the highest power flow contribution degree with the line fault, and preferentially cutting off the unit, so that the optimal capacity of the cutting machine is ensured theoretically.
Optionally, selecting the median of the power flow contribution degree value as a reference value, and performing the optimization of the cutting machine proportion, including:
firstly, generating the capacity of each round of cutting machine according to the running condition of a local power grid, and determining an initial proportion c according to the ratio of the capacity of each round of cutting machine to the total capacity, wherein the initial proportion is 3% -5%;
then selecting the median of the power flow contribution degree value sequences of the power supply units after the sequencing as a reference value of the power flow contribution degree;
finally, comparing the power flow contribution degree of each power supply node with a reference value: if the trend contribution degree is larger than the reference value, the unit cutting proportion can be properly increased by multiplying the ratio of the trend contribution degree to the reference value; if the power flow contribution degree is smaller than the reference value, the cutting machine proportion is defined as the initial proportion c), namely:
wherein PFC is the power flow contribution degree, PFC ref Is a reference value.
The final effect of cutting certain units under different faults is different, in the method, each power plant is tracked according to different faults in countercurrent, the contribution proportion of each power plant to the line is determined, if the value of c% is unreasonable, the reasonability of a final scheme can be ensured through the contribution degree amplification factor, namely the ratio of the power flow contribution degree to a reference value and final overscut verification, if the value of c% is too small, the initial cutting machine quantity is smaller, but the cutting machine proportion of the power plants closely related to the faults can be increased by multiplying the contribution degree amplification factor, the final cutting machine quantity is increased, if the value of c% is too large, the initial cutting machine quantity is larger, but the cutting machine quantity can be limited to be near the maximum cutting capacity by final overscut verification, and the final cutting machine quantity is reduced.
Optionally, the generating the cutting machine quantity of each unit according to the cutting machine proportion, and accumulating the cutting machine quantity includes:
and according to the cutting ratio, multiplying the actual installed capacity of the power plant by the cutting ratio to generate the cutting quantity of each unit of each round, and accumulating the cutting quantity.
Optionally, the step of judging whether the steady-state frequency of the system after cutting meets the steady-state frequency requirement, if yes, finishing the setting, otherwise, repeating the operation until the steady-state frequency of the system after cutting meets the steady-state frequency requirement, wherein the steady-state frequency requirement range of the system after cutting is 49.8-50.2Hz.
Fig. 2 is a flowchart of the whole intelligent setting method of the ac/dc system high-frequency cutting machine according to the above embodiment.
In the embodiment of the application, an ac/dc power grid with 3 machine 10 nodes is taken as an embodiment for analysis, as shown in fig. 3, an electrical wiring diagram of a 3 power plant 10 node ac/dc system provided in the embodiment of the application is shown in fig. 3, and the feasibility of the algorithm is verified by means of a transient simulation software of PSD-BPA (electromagnetic transient intelligent modeling software) of the national electric science institute by taking the example that an outgoing dc line from a bus C to a bus L fails.
Setting 50.5Hz as the first-round operating frequency of the high-frequency cutting machine, 49.2Hz as the first-round low-frequency load shedding frequency, and 5% as the basic cutting machine capacity of each round, namely c=5%, and setting according to the method provided in the application, wherein the whole operation steps are as follows:
(1) Firstly, manually disconnecting an outgoing line of a regional power grid, simulating island operation of the regional power grid, and gradually increasing the cut-off capacity of the regional power grid to enable the system frequency to just reach the action value of 49.2Hz of first-round low-frequency load shedding; as shown in FIG. 4, in the system frequency variation graph for determining the maximum cutting capacity of each round provided in the embodiment of the present application, when the cutting capacity is about 67MW, the minimum frequency of the system reaches 49.19Hz, and the low frequency load shedding is just performed, so that a certain margin is considered, and the maximum cutting capacity P of each round max Taken as 60MW.
(2) Based on the system power flow before the fault, calculating the power flow contribution PFC of each unit corresponding to the direct current line by utilizing a power flow backward tracking technology: the result of the calculation is PFC of the power plant 1 1 0.2380 PFC of the power plant 2 2 PFC of the power plant 3 is 0.2661 3 0.001.
(3) The PFC values are ordered from big to small, the power plants 2, 1 and 3 are sequentially arranged, the power plants 1 and 2 are divided into a group with extremely high association degree, and the power plant 3 is divided into a group with lower association degree.
(4) The median 0.2380 of the PFC values of the power plants after the sorting is selected as the reference value PFC ref And comparing PFC of each power plant with PFC of each power plant to perform cutter ratio optimization: the cutting proportion of the power plant 1 is P cut1 % 5%, the cut-off ratio of the power plant 2 is P cut2 % 5.59%, the cut-off ratio of the power plant 3 is P cut3 % is 5%.
(5) The actual installed capacity of the power plant multiplied by the cut-off ratio is the approximate generator capacity to be cut by the power plant, and then the actual output of each unit of the power plant is reduced to the vicinity of the capacity, if the total cut-off amount is just about the value after cutting off some units of the power plant, the sum of the actual output of the cut-off units is the final cut-off capacity of the power plant. For a large power plant with a plurality of generators, the two generators are not quite different; the actual installed capacity of the power plant is multiplied by the cutting machine proportion of 3 power plants to obtain the cutting machine quantity of each unit, and the cutting machine quantity is accumulated to be 18.61MW and smaller than the maximum cutting machine capacity 60MW, so that verification is passed.
(6) After the rotary cutting measures are adopted, the steady-state frequency of the system is about 50.03Hz and is between 49.8Hz and 50.2Hz, the termination condition is met, and the setting is finished.
The system frequency change taking the present application and the system frequency change taking no action are shown in fig. 5, wherein the line with the reference numeral 1 is a system frequency change curve taking no action, and the line with the reference numeral 2 is a system frequency change curve taking the present application; fig. 6 shows an enlarged portion of the high frequency cutting machine of fig. 5, wherein the line marked 3 is a system frequency variation curve without any measures, and the line marked 4 is a system frequency variation curve with the present application, and it can be seen from the figure that if no measures are taken, not only the system frequency rises to 50.86Hz when about 10.92s (576 th cycle), but also the time when the system frequency is greater than 50.5Hz reaches up to 18.2s (910 cycles), and the final steady-state frequency of the system is about 50.13 Hz. After the application is adopted, in the fault process, the highest frequency of the system is only about 50.57Hz, the transient highest frequency of the system is reduced to some extent, the continuous deterioration trend of the system frequency is avoided, and the system frequency is finally stabilized at about 50.03Hz and is very close to the power frequency of 50Hz, so that the effectiveness of the application is illustrated.
It should be noted that the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that an article or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one … …" does not exclude the presence of other like elements in a process, method, article, or apparatus that comprises the element.
The foregoing is merely a specific embodiment of the application to enable one skilled in the art to understand or practice the application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the application. Thus, the present application is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
It will be understood that the present application is not limited to what has been described above and shown in the drawings, and that various modifications and changes may be made without departing from the scope thereof. The scope of the application is limited only by the appended claims.
Claims (7)
1. An intelligent setting method of an alternating current-direct current system high-frequency cutting machine is characterized by comprising the following steps:
calculating the power flow contribution degree of each power unit node of the power plant after line faults by using a power flow back tracking technology;
sequencing the power flow contribution degrees of the power supply unit nodes according to the values of the power flow contribution degrees from large to small;
selecting the median of the tide contribution degree value as a reference value to perform cutter proportion optimization, wherein the method comprises the following steps:
firstly, generating the capacity of each round of cutting machine according to the running condition of a local power grid, and determining an initial proportion c according to the ratio of the capacity of each round of cutting machine to the total capacity, wherein the initial proportion is 3% -5%;
then selecting the median of the power flow contribution degree value sequences of the power supply units after the sequencing as a reference value of the power flow contribution degree;
finally, comparing the power flow contribution degree of each power supply node with a reference value: if the trend contribution degree is larger than the reference value, the unit cutting proportion can be properly increased by multiplying the ratio of the trend contribution degree to the reference value; if the power flow contribution degree is smaller than the reference value, the cutting machine proportion is defined as the initial proportion c), namely:
wherein PFC is the power flow contribution degree, PFC ref Is a reference value;
generating cutting machine quantity of each unit of each round according to the cutting machine proportion, accumulating the cutting machine quantity to obtain accumulated power and checking the accumulated power, and if the accumulated power is larger than the maximum cutting machine quantity P of the round max Limiting the cutting amount to the maximum cutting amount, if the accumulated power is smaller than the maximum cutting amount P of the wheel max Checking, namely setting the rotary cutting machine object to the unit just by checking;
judging whether the steady-state frequency of the system after cutting meets the steady-state frequency requirement, if so, finishing the setting, otherwise, repeating the operation until the steady-state frequency of the system after cutting meets the steady-state frequency requirement.
2. The intelligent setting method of the high-frequency cutting machine of the alternating current and direct current system according to claim 1, wherein the method further comprises the steps of, before the calculation of the power flow contribution degree of each power plant power unit node after the line fault by using the power flow backward tracking technology,
preprocessing an external line of a local regional power grid, and determining the maximum cutting machine capacity P of each round max 。
3. The intelligent setting method of the ac/dc system high frequency cutting machine according to claim 2, wherein the maximum cutting machine capacity per round P is determined max Comprising:
firstly, disconnecting an outgoing line of a regional power grid, simulating island operation of the regional power grid, and enabling the system frequency to just reach a first-round low-frequency load shedding action value in a mode of gradually increasing the cutting capacity of the regional power grid, wherein the cutting capacity is the maximum cutting capacity P of each round max 。
4. The intelligent setting method of the ac/dc system high frequency cutting machine according to claim 1, wherein the calculating the power flow contribution degree of each power plant power supply unit node after the line fault by using the power flow backward tracking technology comprises:
when the system operates normally, the transmission power from the node i to the adjacent node q is P iq If the i-q line fails, the system will have surplus power P which can not be sent out iq ：
Wherein P is i For the inflow power of node i, P Gk For the power of the generator on the node k, A is a tide inverse tracking coefficient matrix, and an element a in the matrix A ij The method meets the following conditions:
wherein P is j For the inflow power of node j, P ji For node j to transmit power to adjacent node i via line, D i For all the node sets of which the power flows to and is connected with the node i, the power flow contribution degree of the kth generator node of the fault line is as follows:
wherein PFC is provided k And contributing to the tide of the kth generator node.
5. The intelligent setting method of the ac/dc system high-frequency cutting machine according to claim 1, wherein the sequencing the power flow contribution degrees of the power supply unit nodes according to the values of the power flow contribution degrees from large to small further comprises:
after the power flow contribution degree of each power supply node is calculated, firstly sorting is carried out according to the power flow contribution degree, and then the power supply nodes are divided into 3 groups with extremely high relevance [ a,1], relevance [ b, a) and relatively low relevance [0, b) according to step length, wherein a=0.2 and b=0.1.
6. The intelligent setting method of the ac/dc system high frequency cutting machine according to claim 1, wherein the generating the cutting machine amount of each unit according to the cutting machine ratio, and accumulating the cutting machine amounts, comprises:
and according to the cutting ratio, multiplying the actual installed capacity of the power plant by the cutting ratio to generate the cutting quantity of each unit of each round, and accumulating the cutting quantity.
7. The intelligent setting method of the high-frequency cutting machine of the alternating current and direct current system according to claim 1, wherein the method is characterized in that whether the steady-state frequency of the system after cutting machine meets the steady-state frequency requirement is judged, if yes, setting is finished, otherwise, the operation is repeated until the steady-state frequency of the system after cutting machine meets the steady-state frequency requirement, and the steady-state frequency requirement range of the system after cutting machine is 49.8-50.2Hz.
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