CN114552622A - Data-driven dynamic reactive power reserve assessment method for alternating current-direct current hybrid power grid - Google Patents

Data-driven dynamic reactive power reserve assessment method for alternating current-direct current hybrid power grid Download PDF

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CN114552622A
CN114552622A CN202210188429.2A CN202210188429A CN114552622A CN 114552622 A CN114552622 A CN 114552622A CN 202210188429 A CN202210188429 A CN 202210188429A CN 114552622 A CN114552622 A CN 114552622A
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voltage
dynamic reactive
reactive power
fault
current
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罗旭
牛涛
李博
李凡
刘璐桡
田林轩
薛霖
武文国
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Chongqing University
State Grid Corp of China SGCC
Economic and Technological Research Institute of State Grid Chongqing Electric Power Co Ltd
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Chongqing University
State Grid Corp of China SGCC
Economic and Technological Research Institute of State Grid Chongqing Electric Power Co Ltd
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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
    • 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
    • H02J3/12—Circuit arrangements for ac mains or ac distribution networks for adjusting voltage in ac networks by changing a characteristic of the network load
    • H02J3/16—Circuit arrangements for ac mains or ac distribution networks for adjusting voltage in ac networks by changing a characteristic of the network load by adjustment of reactive power
    • 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
    • H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
    • H02J3/46—Controlling of the sharing of output between the generators, converters, or transformers
    • H02J3/50—Controlling the sharing of the out-of-phase component
    • 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
    • H02J2203/00—Indexing scheme relating to details of circuit arrangements for AC mains or AC distribution networks
    • H02J2203/20—Simulating, e g planning, reliability check, modelling or computer assisted design [CAD]
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E40/00—Technologies for an efficient electrical power generation, transmission or distribution
    • Y02E40/30—Reactive power compensation

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Abstract

The invention particularly relates to a data-driven dynamic reactive power reserve assessment method for an alternating current-direct current hybrid power grid, which comprises the following steps: analyzing the voltage stability of the multi-feed-in high-voltage direct-current power transmission system based on the principle and the regulation characteristic of a synchronous phase modulator to generate a corresponding transient voltage curve; smoothing the transient voltage curve in a data driving mode to generate a corresponding pre-processing voltage curve; calculating a corresponding trajectory sensitivity coefficient by increasing the reactive output of the synchronous phase modulator; carrying out quantitative analysis on the severity of the fault of the multi-feed-in high-voltage direct-current transmission system; then combining the preprocessed voltage curve with the corresponding track sensitivity coefficient; and finally, calculating the dynamic reactive power reserve capacity meeting the voltage safety constraint through a stepping search algorithm. The dynamic reactive power reserve assessment method can improve the calculation precision and the solving efficiency of the dynamic reactive power reserve assessment, and therefore the stability of the operation control of the power system can be improved in an auxiliary mode.

Description

Data-driven dynamic reactive power reserve assessment method for alternating current-direct current hybrid power grid
Technical Field
The invention relates to the technical field of power system operation control, in particular to a dynamic reactive power reserve assessment method for an alternating current-direct current hybrid power grid based on data driving.
Background
At present, new energy sources typified by wind power and photovoltaic power generation are mainly distributed in the western regions of china, and loads are mainly distributed in the southeast regions of china. The converter-based high-voltage direct-current transmission system is used as an important energy transmission channel, and can remarkably improve the utilization efficiency and the consumption level of new energy. In the east and southeast regions of china, grid structures have been formed for multi-feed high voltage direct current transmission systems. However, due to the high load density of the receiving end power grid, the electrical distance between the dc drop points is short, and therefore the stability of the power system is greatly challenged.
As a key device for commutation, a thyristor has no self-turn-off capability, and when a receiving-end alternating current power grid fails, a high-voltage direct current transmission system often fails in commutation. After three consecutive commutation failures occur, a direct current blocking is triggered, large-scale power transfer is caused, and more serious harm is caused. Therefore, it is a very important issue to reasonably evaluate how much dynamic reactive power reserve should be reserved by the dynamic reactive device and ensure the voltage stability when the fault occurs. For example, chinese patent publication No. CN109038636A discloses a "method for evaluating dynamic reactive power reserve requirement of a data-driven dc-receiving grid", which quantitatively evaluates the transient voltage stability of the near region of a dc-inverting converter station by using an index, iteratively calculates the dynamic reactive power reserve requirement of the near region of the dc-inverting converter station based on numerical simulation, and stores the calculation result and characteristic quantity into an offline sample library.
The dynamic reactive power reserve (demand) assessment method in the existing scheme reads operation mode data from a power grid on line, then extracts characteristic quantities of an on-line system, and further rapidly assesses the dynamic reactive power reserve demand on line by using a data mining model. The applicant finds that the existing dynamic reactive power reserve assessment problem can be abstracted as a tscopf (transient stability constraints optimal power flow) problem. However, in the prior art, the solution time of the tscopf problem is long, and the time for planning and scheduling the power system is only 5-15 minutes, that is, the evaluation efficiency of the dynamic reactive power reserve is low, so that the existing scheme is difficult to meet the requirement of the operation control stability of the power system. Therefore, how to design a method capable of improving both the calculation accuracy and the solution efficiency of the dynamic reactive power reserve assessment is an urgent technical problem to be solved.
Disclosure of Invention
Aiming at the defects of the prior art, the technical problems to be solved by the invention are as follows: how to provide a data-driven AC/DC hybrid power grid dynamic reactive reserve assessment method to improve the calculation precision and the solution efficiency of dynamic reactive reserve assessment, so that the stability of the operation control of a power system can be improved in an auxiliary manner.
In order to solve the technical problems, the invention adopts the following technical scheme:
the data-driven AC/DC hybrid power grid dynamic reactive power reserve evaluation method comprises the following steps:
s1: analyzing the voltage stability of the multi-feed-in high-voltage direct-current power transmission system based on the principle and the regulation characteristic of a synchronous phase modulator to generate a corresponding transient voltage curve;
s2: smoothing the transient voltage curve in a data driving mode to generate a corresponding pre-processing voltage curve;
s3: calculating a corresponding trajectory sensitivity coefficient by increasing the reactive output of the synchronous phase modulator;
s4: carrying out quantitative analysis on the severity of the fault of the multi-feed-in high-voltage direct-current transmission system; then combining the preprocessed voltage curve with the corresponding track sensitivity coefficient; and finally, calculating the dynamic reactive power reserve capacity meeting the voltage safety constraint through a stepping search algorithm.
Preferably, step S1 specifically includes the following steps:
s101: building a corresponding multi-feed-in high-voltage direct-current power transmission system model based on the actual condition of the alternating-current and direct-current hybrid power grid;
s102: setting relevant parameters of a multi-feed-in high-voltage direct-current power transmission system model;
s103: the principle and the regulation characteristic of the synchronous phase modulator are researched, and the fault of the multi-feed-in high-voltage direct-current power transmission system model can be simulated on the basis of the characteristic that the synchronous phase modulator can continuously regulate reactive power so as to analyze the voltage stability of the multi-feed-in high-voltage direct-current power transmission system and further generate a corresponding transient voltage curve.
Preferably, in step S102, the rectifying side of the multi-feed-in high-voltage direct-current transmission system model adopts constant current control and minimum firing angle control, and the inverting side adopts constant current control and constant extinction angle control.
Preferably, in step S103, the electromagnetic transient simulation software is used to simulate the voltage waveform of the multi-fed hvdc transmission system after the fault, so as to generate a corresponding transient voltage curve.
Preferably, in step S2, the transient voltage curve is smoothed based on a data fitting method of the improved Powell algorithm.
Preferably, in step S2, on the basis of the preprocessed voltage curve, the relationship between the turn-off angle of the converter station in the ac/dc hybrid power grid and the related electrical parameter is approximated to a corresponding high-term polynomial.
Preferably, in step S3, the trajectory sensitivity coefficient is calculated by the following formula:
K＝ΔU/ΔQ；
in the formula: k represents a track sensitivity coefficient; Δ U represents a bus bar voltage variation amount; and deltaQ represents the reactive power variation of the synchronous phase modulator.
Preferably, in step S4, a fault severity calculation index defined based on the voltage drop area is designed based on the preprocessed voltage curve, so as to quantitatively analyze the severity of different faults.
Preferably, the severity of the fault is defined by integrating the voltage drop area when the fault occurs and the voltage recovery level after the fault, and then quantitative analysis is carried out on the severity of the fault through the specific relationship between the short-circuit ratio and the electrical distance between the receiving ends and the severity of the fault.
Preferably, in step S4, the formula of the voltage safety constraint is as follows:
U0+K*ΔQ≥0.85p.u.；
in the formula: u shape0Representing the initial value of the bus voltage under the current condition; delta Q represents the reactive output variation of the synchronous phase modulator; k represents the track sensitivity of the influence of the reactive output of the synchronous phase modulator on the bus voltage; p.u represents a per unit value.
The method for evaluating the dynamic reactive power reserve of the alternating current-direct current hybrid power grid has the following beneficial effects:
the invention analyzes the voltage stability of the multi-feed high-voltage direct-current transmission system and generates a transient voltage curve through the principle and the regulation characteristic of the synchronous phase modulator, then calculating the corresponding track sensitivity coefficient by increasing the reactive output of the synchronous phase modulator, so that the dynamic reactive reserve capacity meeting the voltage safety constraint can be accurately calculated through sensitivity analysis (track sensitivity coefficient) and a step search algorithm, the method has the advantages that the method can greatly accelerate the solving speed, can improve the calculation precision and the solving efficiency of dynamic reactive power reserve evaluation, and can assist in improving the stability of the operation control of the power system.
According to the dynamic reactive power reserve capacity calculation method, the transient voltage curve is subjected to smoothing processing in a data driving mode to generate the preprocessed voltage curve, the transient voltage curve can be simplified within an error allowable range, the dynamic reactive power reserve capacity can be calculated based on the smoother preprocessed voltage curve, and therefore the accuracy and the solving efficiency in dynamic reactive power reserve evaluation can be further improved.
According to the method, the severity of the fault of the multi-feed-in high-voltage direct-current power transmission system is quantitatively analyzed, and the severity of the fault can be quantitatively expressed, so that the calculation of the dynamic reactive power reserve capacity can be assisted, namely the solution of the tscopf problem is better realized.
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For purposes of promoting a better understanding of the objects, aspects and advantages of the invention, reference will now be made in detail to the present invention as illustrated in the accompanying drawings, in which:
fig. 1 is a logic block diagram of a data-driven ac/dc hybrid power grid dynamic reactive power reserve evaluation method;
FIG. 2 is a model of a multi-feed HVDC transmission system for building
FIG. 3 is a diagram illustrating a transient voltage stability indicator;
FIG. 4 is a schematic diagram of reactive voltage sensitivity;
FIG. 5 is a comparison of arc-extinguishing angle curves before and after dynamic reactive power optimization;
fig. 6 is a comparison of voltage curves before and after dynamic reactive power optimization (single-phase earth fault);
fig. 7 is a comparison of voltage curves before and after dynamic reactive power optimization (three-phase earth fault).
Detailed Description
The following is further detailed by the specific embodiments:
example (b):
in the prior art, a least square method is generally adopted for solving a tscopp (transient stability constraints) optimal power flow problem, and differential algebraic equations describing transient processes need to be considered, but the equations describing the dynamic characteristics of the converter station have the characteristics of high order, strong rigidity and time variation, and are difficult to directly analyze and process.
The general expression of the least squares method is as follows:
Figure BDA0003524529180000041
Figure BDA0003524529180000042
Figure BDA0003524529180000043
Y＝[y1,y2,y3……yn]T
X＝[A1…Am,B1…Bm,…G1…Gm]T
Figure BDA0003524529180000044
Figure BDA0003524529180000045
the existing least squares method has its inherent limitations: the method is sensitive to sample points of abnormal data, and in the process of fitting the multivariate unknown parameters, a proper steepest descent method needs to be found to obtain a reasonable iteration solution, and in the process, the solved inverse matrix does not exist or an initial value distance may be met.
In order to solve the problem of solving the existing tscopf problem, the applicant further designs the technical scheme of the embodiment.
The embodiment of the invention discloses a dynamic reactive power reserve assessment method for an alternating current-direct current hybrid power grid based on data driving.
As shown in fig. 1, the data-driven ac/dc hybrid power grid dynamic reactive power reserve evaluation method includes the following steps:
s1: analyzing the voltage stability of the multi-feed-in high-voltage direct-current power transmission system based on the principle and the regulation characteristic of a synchronous phase modulator to generate a corresponding transient voltage curve;
s2: smoothing the transient voltage curve in a data driving mode to generate a corresponding pre-processing voltage curve;
s3: calculating a corresponding trajectory sensitivity coefficient by increasing the reactive output of the synchronous phase modulator;
s4: carrying out quantitative analysis on the severity of the fault of the multi-feed-in high-voltage direct-current transmission system; then combining the preprocessed voltage curve with the corresponding track sensitivity coefficient; and finally, calculating the dynamic reactive power reserve capacity meeting the voltage safety constraint through a stepping search algorithm. In this embodiment, calculating the dynamic reactive reserve capacity may be regarded as solving a tscopf (transient stability constraints optimal power flow) problem. The step search algorithm is an existing mature algorithm, and reactive output of a synchronous phase modulator is sequentially increased according to fixed amplification until bus voltage is recovered to a critical value of system stability.
It should be noted that, by the reactive voltage supporting function of the synchronous phase modulator during the fault, the invention can reduce the voltage drop amplitude and improve the voltage stability, thereby greatly reducing the active loss of the power transmission system and improving the economy.
The invention analyzes the voltage stability of the multi-feed high-voltage direct-current transmission system and generates a transient voltage curve through the principle and the regulation characteristic of the synchronous phase modulator, then calculating the corresponding track sensitivity coefficient by increasing the reactive output of the synchronous phase modulator, so that the dynamic reactive reserve capacity meeting the voltage safety constraint can be accurately calculated through sensitivity analysis (track sensitivity coefficient) and a step search algorithm, the method has the advantages that the method can greatly accelerate the solving speed, can improve the calculation precision and the solving efficiency of dynamic reactive power reserve evaluation, and can assist in improving the stability of the operation control of the power system. Secondly, the transient voltage curve is smoothed in a data driving mode to generate a preprocessed voltage curve, the transient voltage curve can be simplified within an error allowable range, dynamic reactive power reserve capacity can be calculated based on the smoother preprocessed voltage curve, and therefore precision and solving efficiency in dynamic reactive power reserve evaluation can be further improved. Finally, the severity of the fault can be quantitatively expressed by quantitatively analyzing the severity of the fault of the multi-feed-in high-voltage direct-current power transmission system, so that the calculation of the dynamic reactive power reserve capacity can be assisted, namely the solution of the tscopf problem can be better realized.
In step S1, the method specifically includes the following steps:
s101: as shown in fig. 2, a corresponding multi-feed-in high-voltage direct-current power transmission system model is built based on the actual situation of the alternating-current/direct-current hybrid power grid; in the embodiment, a multi-feed-in high-voltage direct-current power transmission system model is built through electromagnetic transient simulation software (PSCAD/EMTDC), the PSCAD/EMTDC is electromagnetic transient simulation software widely used in the world, the EMTDC is a simulation calculation core of the PSCAD/EMTDC, and the PSCAD provides a graphical operation interface for the EMTDC (electromagnetic transitions including DC).
S102: setting relevant parameters of a multi-feed-in high-voltage direct-current power transmission system model; in this embodiment, the rectification side of the multi-feed-in high-voltage direct-current power transmission system model adopts constant current control and minimum trigger angle control, and the inversion side adopts constant current control and constant extinction angle control.
S103: the principle and the regulation characteristic of the synchronous phase modulator are researched, and the fault of the multi-feed-in high-voltage direct-current power transmission system model is simulated based on the characteristic that the synchronous phase modulator can continuously regulate the reactive power so as to analyze the voltage stability of the multi-feed-in high-voltage direct-current power transmission system and further generate a corresponding transient voltage curve. In this embodiment, the voltage waveform of the multi-feed-in high-voltage direct-current power transmission system model after the fault is simulated by using electromagnetic transient simulation software (PSCAD/EMTDC), so as to generate a corresponding transient voltage curve.
According to the method, the multi-feed-in high-voltage direct-current transmission system model is constructed, relevant parameters are set, the principle and the regulation characteristic of the synchronous phase modulator are researched, and the fault of the multi-feed-in high-voltage direct-current transmission system model can be simulated based on the characteristic that the synchronous phase modulator can continuously regulate the reactive power, so that the voltage stability of the multi-feed-in high-voltage direct-current transmission system can be effectively analyzed, a transient voltage curve can be generated better to complete the evaluation of the dynamic reactive power reserve capacity, and the solution of the tscopf problem can be better realized.
In the specific implementation process, the transient voltage curve is smoothed by a data fitting method based on an improved Powell algorithm. On the basis of preprocessing a voltage curve, approximating the relation between the turn-off angle of a converter station in the AC/DC hybrid power grid and related electrical parameters to a corresponding high-term polynomial. In the present embodiment, the applicant found that the transient voltage curve has strong rigidity and many burrs, and the direct analysis is not favorable for solving the problem. The approximation is converted into a smooth curve, i.e. a pre-processed voltage curve, by means of data fitting.
According to the invention, the transient voltage curve is smoothed by improving a data fitting method of a Powell algorithm, and the transient voltage curve can be simplified within an error allowable range, so that the dynamic reactive power reserve capacity can be better calculated based on a smoother preprocessed voltage curve, namely, the solution of the tscopf problem can be better realized.
In a specific implementation process, the track sensitivity coefficient is calculated by the following formula:
K＝ΔU/ΔQ；
in the formula: k represents a track sensitivity coefficient; Δ U represents a bus bar voltage variation amount; and deltaQ represents the reactive power variation of the synchronous phase modulator.
In the specific implementation process, the formula of the voltage safety constraint is as follows:
U0+K*ΔQ≥0.85p.u.；
in the formula: u shape0Representing the initial value of the bus voltage under the current condition; delta Q represents the reactive output variation of the synchronous phase modulator; k represents the track sensitivity of the influence of the reactive output of the synchronous phase modulator on the bus voltage; p.u represents a per unit value.
In this embodiment, the trajectory sensitivity definition method is shown in fig. 3, and the quantitative relationship between the reactive power change and the voltage change is mainly described by comparing the changes of the bus voltage curve trajectories before and after the dynamic reactive power change. The sensitivity of the reactive voltage is shown in fig. 4.
In the specific implementation process, a fault severity calculation index defined based on a voltage drop area is designed based on a preprocessed voltage curve, and the fault severity calculation index is used for quantitatively analyzing the severity of different faults. The severity of the fault is defined by integrating the voltage drop area when the fault occurs and the voltage recovery level after the fault, and then quantitative analysis is carried out on the severity of the fault through the specific relation between the short-circuit ratio and the electrical distance between the receiving ends and the severity of the fault. In this embodiment, a three-phase short-circuit fault is set in the established double-fed high-voltage direct-current power transmission system model, different short-circuit ratios (corresponding to the strengths of power transmission systems) and different electrical distances (corresponding to the strengths of electrical coupling relations between systems) are set respectively for comparing the influences of different factors on the severity of the fault, and the sizes of the voltage drop areas corresponding to the short-circuit ratios and the electrical distances are calculated respectively, so that the exact relations between various factors and the severity of the fault are intuitively and specifically reflected.
According to the invention, through designing the fault severity calculation index defined based on the voltage drop area, the severity of different faults can be effectively and quantitatively analyzed, the severity of the faults can be quantitatively expressed, and the indexes such as the short-circuit ratio, the electrical distance and the like are verified and processed to respectively correspond to the strength of a high-voltage direct-current power transmission system and the strength of the electrical coupling relation between different systems, so that the calculation of dynamic reactive power reserve capacity can be assisted, namely the solution of the tscopf problem can be better realized.
In order to better illustrate the advantages of the technical solution of the present invention, the following examples are disclosed in the present implementation:
example one:
and calculating the voltage drop area of the same fault under different short circuit ratios and different electrical distances.
Firstly, a transient voltage evaluation index (expressed by a voltage drop area) suitable for the direct-current power transmission system is established on the basis of a voltage waveform diagram after fault simulation by comprehensively considering various factors such as the voltage drop degree during fault, the voltage recovery level after fault, the voltage recovery time and the like.
The influence of the strength of the high-voltage direct-current transmission system and the electric coupling relation between different systems on the severity of the fault is studied one by a variable control method, and specific example analysis results are shown in table 1.
TABLE 1 calculation of the voltage sag area under different conditions
Figure BDA0003524529180000071
As can be seen from table 1, the larger the short-circuit ratio is, the smaller the voltage drop area is, which indicates that the transient voltage supporting capability of the ac system is stronger under the N-1 fault; on the other hand, the electrical distance between the receiving end grids also influences the calculation result of the final voltage security domain. As can be seen from table 1, when the electrical distance between different subsystems is smaller, the electrical coupling effect between the subsystems is stronger, and the corresponding fault influence range is wider, so that it is very necessary to analyze the coupling relationship between the different subsystems when analyzing the operation characteristics of the hvdc transmission system.
Example two:
different faults and parameters thereof are set respectively, and aiming at the same fault under the same condition, the dynamic reactive reserve capacity is solved respectively by directly solving the tscopf problem and applying the method provided by the invention, and the final result is compared, so that the final result shows that the dynamic reactive reserve evaluation method based on data driving can greatly improve the solving speed (without solving the complicated tscopf problem) while ensuring certain precision, and the voltage stability is remarkably improved by testing the voltage curves before and after reactive optimization, and the stability of the voltage is all up to more than 0.85, as shown in table 2.
Table 2 example detailed fault information of dynamic reactive power reserve evaluation and calculation result thereof
Figure BDA0003524529180000072
Figure BDA0003524529180000081
Table 3 power grid loss comparison table with or without synchronous phase modulator
Figure BDA0003524529180000082
As shown in table 3, it can be seen that the active loss of the three-phase ground fault is far greater than that of the single-phase ground fault through the active loss of the single-phase ground fault and the three-phase ground fault when the synchronous phase modulator is not provided, and after the synchronous phase modulator is installed, the reactive voltage supporting function of the synchronous phase modulator during the fault is utilized, so that the voltage reduction amplitude can be reduced, the voltage stability is improved, the active loss of a power transmission system can be greatly reduced, and the economical efficiency is improved.
After dynamic reactive power optimization using the given method, the arc-extinguishing angle vibration amplitude is greatly reduced and tends to be stable more quickly, as shown in fig. 5. In the high-voltage direct-current transmission system, the extinction angle is a standard for judging whether phase commutation fails or not, and when the extinction angle is smaller than a certain threshold value, the phase commutation fails. Before dynamic reactive power optimization, the arc-quenching angle curve oscillates violently and is close to 0 degree for multiple times, which represents that multiple commutation failures occur, and direct current blocking is probably triggered to cause large-scale power transfer; after dynamic reactive power optimization, the extinction angle quickly tends to be stable and is always above a threshold value, so that continuous commutation failure is effectively prevented, and the stability and the safety of the high-voltage direct-current power transmission system are obviously improved.
As shown in fig. 6 and 7, the two graphs respectively represent the voltage curve change graphs before and after the dynamic reactive power optimization in the case of the unidirectional ground fault and the three-phase ground fault, and it can be seen from the graphs that after the reactive power optimization is performed by the method provided by the present invention, the bus voltage level after the fault is cleared is rapidly recovered to above 0.85, which effectively avoids the occurrence of the continuous commutation failure and maintains the safety and stability of the system.
From the results, the method provided by the invention can effectively and quantitatively analyze how much dynamic reactive reserve needs to be reserved for the synchronous phase modulator, the provided model solves the problems of high non-linearity degree, more constraint conditions, large solving difficulty, long solving time and the like in the traditional tscopf solving problem, the data-driven algorithm based on the improved Powell algorithm establishes the voltage simulation curve to be idealized, the trajectory sensitivity analysis method approximately linearizes the relation between reactive and voltage, and the evaluation method of the dynamic reactive reserve model is further perfected.
Finally, it should be noted that the above embodiments are only used for illustrating the technical solutions of the present invention and not for limiting the technical solutions, and those skilled in the art should understand that modifications or equivalent substitutions can be made on the technical solutions of the present invention without departing from the spirit and scope of the technical solutions, and all that should be covered by the claims of the present invention.

Claims (10)

1. The data-driven AC/DC hybrid power grid dynamic reactive power reserve evaluation method is characterized by comprising the following steps of:
s1: analyzing the voltage stability of the multi-feed-in high-voltage direct-current power transmission system based on the principle and the regulation characteristic of a synchronous phase modulator to generate a corresponding transient voltage curve;
s2: smoothing the transient voltage curve in a data driving mode to generate a corresponding pre-processing voltage curve;
s3: calculating a corresponding trajectory sensitivity coefficient by increasing the reactive output of the synchronous phase modulator;
s4: carrying out quantitative analysis on the severity of the fault of the multi-feed-in high-voltage direct-current transmission system; then combining the preprocessed voltage curve with the corresponding track sensitivity coefficient; and finally, calculating the dynamic reactive power reserve capacity meeting the voltage safety constraint through a stepping search algorithm.
2. The method for evaluating the dynamic reactive power reserve of the AC-DC hybrid power grid based on the data driving as claimed in claim 1, wherein: in step S1, the method specifically includes the following steps:
s101: building a corresponding multi-feed-in high-voltage direct-current power transmission system model based on the actual condition of the alternating-current and direct-current hybrid power grid;
s102: setting relevant parameters of a multi-feed-in high-voltage direct-current power transmission system model;
s103: the principle and the regulation characteristic of the synchronous phase modulator are researched, and the fault of the multi-feed-in high-voltage direct-current power transmission system model is simulated based on the characteristic that the synchronous phase modulator can continuously regulate the reactive power so as to analyze the voltage stability of the multi-feed-in high-voltage direct-current power transmission system and further generate a corresponding transient voltage curve.
3. The method for evaluating the dynamic reactive power reserve of the AC-DC hybrid power grid based on the data driving as claimed in claim 2, wherein: in step S102, the rectifying side of the multi-feed-in high-voltage direct-current transmission system model adopts constant current control and minimum firing angle control, and the inverting side adopts constant current control and constant extinction angle control.
4. The method for evaluating the dynamic reactive power reserve of the AC-DC hybrid power grid based on the data driving as claimed in claim 2, wherein: in step S103, the electromagnetic transient simulation software is used to simulate the voltage waveform of the multi-feed-in hvdct model after a fault, so as to generate a corresponding transient voltage curve.
5. The method for evaluating the dynamic reactive power reserve of the AC-DC hybrid power grid based on the data driving as claimed in claim 1, wherein: in step S2, the transient voltage curve is smoothed based on a data fitting method of the improved Powell algorithm.
6. The method for evaluating the dynamic reactive power reserve of the AC-DC hybrid power grid based on the data driving as claimed in claim 1, wherein: in step S2, on the basis of preprocessing the voltage curve, the relationship between the turn-off angle of the converter station in the ac/dc hybrid power grid and the relevant electrical parameter is approximated to a corresponding high-term polynomial.
7. The method for evaluating the dynamic reactive power reserve of the AC-DC hybrid power grid based on the data driving as claimed in claim 1, wherein: in step S3, the trajectory sensitivity coefficient is calculated by the following formula:
K＝ΔU/ΔQ；
in the formula: k represents a track sensitivity coefficient; Δ U represents a bus bar voltage variation amount; and deltaQ represents the reactive power variation of the synchronous phase modulator.
8. The method for evaluating the dynamic reactive power reserve of the AC-DC hybrid power grid based on the data driving as claimed in claim 1, wherein: in step S4, a fault severity calculation index defined based on the voltage sag area is designed based on the preprocessed voltage curve, so as to quantitatively analyze the severity of different faults.
9. The method for evaluating the dynamic reactive power reserve of the AC-DC hybrid power grid based on the data driving as claimed in claim 8, wherein: and the severity of the fault is defined by integrating the voltage drop area when the fault occurs and the voltage recovery level after the fault, and then the quantitative analysis of the severity of the fault is realized through the specific relation between the short-circuit ratio and the electrical distance between the receiving ends and the severity of the fault.
10. The method for evaluating the dynamic reactive power reserve of the AC-DC hybrid power grid based on the data driving as claimed in claim 1, wherein: in step S4, the formula of the voltage safety constraint is as follows:
U0+K*ΔQ≥0.85p.u.；
in the formula: u shape0Representing the initial value of the bus voltage under the current condition; delta Q represents the reactive output variation of the synchronous phase modulator; k represents the track sensitivity of the influence of the reactive output of the synchronous phase modulator on the bus voltage; p.u represents a per unit value.
CN202210188429.2A 2022-02-28 2022-02-28 Data-driven dynamic reactive power reserve assessment method for alternating current-direct current hybrid power grid Pending CN114552622A (en)

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Publication number Priority date Publication date Assignee Title
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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN116093952A (en) * 2023-03-06 2023-05-09 国网浙江省电力有限公司温州供电公司 Transient voltage stability monitoring bus analysis method

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