CN117674116A - Identification method and device for broadband oscillation risk of alternating current-direct current series-parallel system - Google Patents
Identification method and device for broadband oscillation risk of alternating current-direct current series-parallel system Download PDFInfo
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Abstract
The invention discloses a method and a device for identifying broadband oscillation risks of an alternating current-direct current series-parallel system, which are used for generating an oscillation influence factor matrix according to an acquired broadband oscillation quantitative evaluation index, further generating an oscillation modal parameter matrix, and identifying the broadband oscillation risks by calculating Copula entropy of a plurality of sub-frequency intervals and carrying out correlation analysis. Compared with the prior art, the method and the device have the advantages that key influence factors of broadband oscillation are quantitatively analyzed through Copula entropy, so that key influence factors of broadband oscillation of an alternating-current and direct-current series-parallel system are analyzed, and accurate and reliable basis is provided for follow-up oscillation suppression through relevant methods such as targeted adjustment.
Description
Technical Field
The invention belongs to the technical field of alternating current-direct current series-parallel systems, and particularly relates to a method and a device for identifying broadband oscillation risks of an alternating current-direct current series-parallel system.
Background
As grid commutators (LCCs) and Voltage Source Converters (VSCs) are connected to the grid, the degree of power electronics of the power system is significantly increased, and multiple time scale control systems in the power electronics power system interact with devices in the grid, which can lead to oscillation instability in the system broadband, resulting in an increased risk of system oscillations. The broadband oscillation can cause system power fluctuation, so that grid linkage accidents occur, and the safe and stable operation of the power system is seriously jeopardized.
In order to reduce the damage of broadband oscillation, when the oscillation occurs, the key influencing factors of the oscillation need to be analyzed, so that the subsequent suppression of the oscillation by a relevant method such as targeted adjustment is facilitated.
The patent CN116307738A discloses a method and a device for identifying the risk of broadband oscillation of a power system, wherein the method comprises the following steps: determining the damping ratio of the power system under each working condition combination according to the grid-connected impedance characteristics of the equipment to be grid-connected and the power system under each working condition combination; clustering analysis is carried out on the working condition combinations with the damping ratio smaller than the oscillation threshold value of the power system, and broadband oscillation risk points are determined; the scheme can effectively, conveniently and accurately identify the risk points which are easy to cause broadband oscillation in the power system.
Patent CN116953424a presents a method and system for assessing the risk of broadband oscillations of an electrical power system, the method comprising: acquiring broadband measurement data uploaded by a broadband measurement device at a station end in the electric power system, and acquiring fundamental wave and inter-harmonic data of electric equipment in the electric power system based on the broadband measurement data; screening out electric equipment which is based on the current oscillation mode in the electric power system and participates in oscillation in the oscillation mode based on fundamental wave and inter-harmonic wave data, and obtaining the damping ratio of the electric power system in the oscillation mode based on the fundamental wave and inter-harmonic wave data corresponding to the electric equipment which is based on the current oscillation mode in the electric power system and participates in oscillation in the oscillation mode; and according to the obtained damping ratio, carrying out oscillation risk identification, and evaluating the broadband oscillation risk of the power system according to the obtained identification result. The implementation of the scheme can sense the oscillation risk in advance and push the early warning information.
However, as in the prior art, the corresponding variable factors are considered to be relatively one-sided when performing the wideband oscillation risk identification evaluation. Therefore, how to fuse the parameter indexes of the oscillation modes to realize the broadband oscillation risk identification based on the key influencing factors is a problem to be solved by those skilled in the art.
Disclosure of Invention
Aiming at the defects in the prior art, the invention provides a method and a device for identifying broadband oscillation risk of an alternating current-direct current series-parallel system, wherein the method comprises the following steps: acquiring a broadband oscillation quantitative evaluation index, generating an oscillation influence factor matrix based on the broadband oscillation quantitative evaluation index, and carrying out normalization processing; based on the oscillation influence factor matrix after normalization processing, generating an oscillation mode parameter matrix by combining the division of frequency intervals; and carrying out parameter estimation on the oscillation influence factor matrix and the oscillation modal parameter matrix through a Copula function to finish the identification of the broadband oscillation risk of the alternating current-direct current hybrid system. Compared with the prior art, the method and the device have the advantages that key influence factors of broadband oscillation are quantitatively analyzed through Copula entropy, so that key influence factors of broadband oscillation of an alternating-current and direct-current series-parallel system are analyzed, and accurate and reliable basis is provided for follow-up oscillation suppression through relevant methods such as targeted adjustment.
In a first aspect, the invention provides a method for identifying broadband oscillation risk of an ac/dc series-parallel system, which specifically comprises the following steps:
acquiring a broadband oscillation quantitative evaluation index, generating an oscillation influence factor matrix based on the broadband oscillation quantitative evaluation index, and carrying out normalization processing;
based on the oscillation influence factor matrix after normalization processing, generating an oscillation mode parameter matrix by combining the division of frequency intervals;
and carrying out parameter estimation on the oscillation influence factor matrix and the oscillation modal parameter matrix through a Copula function to finish the identification of the broadband oscillation risk of the alternating current-direct current hybrid system.
According to the method, key influence factors of broadband oscillation of the alternating current-direct current hybrid system are analyzed quantitatively through Copula entropy, so that key influence factors of broadband oscillation of the alternating current-direct current hybrid system are analyzed, and accurate and reliable basis is provided for subsequent oscillation inhibition through relevant methods such as targeted adjustment.
Further, the wideband oscillation quantization evaluation index includes a generator output, a load of an ac-dc series-parallel system, a controller PI parameter of the LCC and/or the VSC, and a phase-locked loop PI parameter.
Further, the normalization process includes: normalizing each column in the oscillation influence factor matrix, specifically expressed as:
Wherein X is ij Is the ith row and jth column element,is the normalization of the ith row and jth column elementsConversion value, X jmin Is the j-th column element X j Minimum value of X jmax Is the j-th column element X j Is a maximum value of (a).
Further, based on the oscillation influence factor matrix after normalization processing, and in combination with the division of the frequency interval, an oscillation mode parameter matrix is generated, which specifically comprises the following steps:
dividing the frequency interval to obtain a plurality of sub-frequency intervals;
applying voltage step disturbance of preset frequency at the concerned node, obtaining a voltage disturbance response signal and a current disturbance response signal, and giving an impedance characteristic matrix of the alternating current-direct current series-parallel system, wherein the preset frequency is determined by each sub-frequency interval;
analyzing determinant zero points of an impedance characteristic matrix of the alternating current-direct current series-parallel system, determining oscillation modes of the alternating current-direct current series-parallel system in each sub-frequency interval according to the determinant zero points, and obtaining corresponding damping:
and carrying out normalization processing on damping in each sub-frequency interval to construct an oscillation modal parameter matrix.
Further, the frequency interval is divided to obtain a plurality of sub-frequency intervals, which specifically includes:
dividing the frequency interval in a linear equal width or logarithmic equal width mode to obtain a plurality of sub-frequency intervals, wherein the identification error of each sub-frequency interval is within a preset threshold range.
Further, the identification error of each sub-frequency interval is within a preset threshold range, which specifically includes: comparing the identification error with a preset threshold range, and confirming that the identification error is within the preset threshold by performing bipartite and re-identification solving on the sub-frequency interval.
Further, the identification error of the sub-frequency interval is specifically expressed as:
wherein e r H (jω) is the identification error of the sub-frequency interval i ) Is sub-frequencyActual value of frequency response of rate interval, H mea (jω i ) And n is the number of data points adopted by the sub-frequency interval.
Further, applying a voltage step disturbance of a preset frequency at the node of interest specifically includes: d-axis and q-axis voltage disturbances of a preset frequency are injected separately at the node of interest.
Further, the impedance characteristic matrix of the ac/dc series-parallel system is specifically expressed as:
wherein Z is total (s) is an impedance characteristic matrix of an alternating current-direct current series-parallel system, and Deltau d1 、△u q1 For the d-axis and q-axis voltage disturbance response signals when the d-axis disturbance is injected alone, deltai d1 、Δi q1 For d-axis and q-axis current disturbance response signals when d-axis disturbance is injected alone, deltau d2 、△u q2 For the d-axis and q-axis voltage disturbance response signals when the q-axis disturbance is injected alone, Δi d2 、Δi q2 For injecting the d-axis and q-axis current disturbance response signals when the q-axis disturbance is injected alone, Z dd 、Z dq 、Z qd 、Z qq Is Z total Four elements in(s).
Further, analyzing determinant zero points of an impedance characteristic matrix of the alternating current-direct current series-parallel system specifically comprises the following steps:
determinant calculation is carried out on an impedance characteristic matrix of the alternating current-direct current series-parallel system, and the determinant calculation is specifically expressed as follows:
det(Z total )＝Z dd Z qq -Z dq Z qd
wherein det () is a determinant calculation function;
and obtaining determinant zero points of the impedance characteristic matrix of the alternating current-direct current hybrid system by analyzing determinant calculation results of the impedance characteristic matrix of the alternating current-direct current hybrid system.
Further, parameter estimation is carried out on the oscillation influence factor matrix and the oscillation modal parameter matrix through a Copula function, so that the identification of the broadband oscillation risk of the alternating current-direct current series-parallel system is completed, and the method specifically comprises the following steps:
carrying out parameter estimation on random variables in the oscillation influence factor matrix and the oscillation modal parameter matrix through the Copula function to obtain a Copula density function, and analyzing Copula entropy of influence factor variables and damping variables in each sub-frequency interval;
according to the Copula entropy obtained by analysis, the random variables in the oscillation influence factor matrix are ordered, key influence factors of the broadband oscillation of the system are determined based on the ordering result, and the broadband oscillation risk identification is carried out according to the key factors.
Further, copula entropy of influencing factor variables and damping variables in each sub-frequency interval is analyzed, and the Copula entropy is specifically expressed as:
where H () is the Copula entropy, c () is the Copula density function,normalized value for the j-th column influence factor variable, < ->Normalized value of damping variable for kth subfrequency interval,/>Normalized value of the factor variable in the j-th column in the i-th operating state, +.>And N is the total number of the running states, wherein the normalized value is the damping variable of the kth subfrequency section in the ith running state.
Further, the larger the Copula entropy value, the higher the risk of oscillation corresponding to the preset frequency.
In a second aspect, the present invention further provides a device for identifying a broadband oscillation risk of an ac/dc hybrid system, which adopts the method for identifying a broadband oscillation risk of an ac/dc hybrid system, including:
the oscillation influence factor matrix generation module is used for acquiring broadband oscillation quantitative evaluation indexes, generating an oscillation influence factor matrix based on the broadband oscillation quantitative evaluation indexes, and carrying out normalization processing;
the oscillation modal parameter matrix generation module is used for generating an oscillation modal parameter matrix based on the oscillation influence factor matrix after normalization processing and combining the division of the frequency interval;
And the broadband oscillation risk assessment module is used for carrying out parameter estimation on the oscillation influence factor matrix and the oscillation modal parameter matrix through the Copula function so as to complete identification of broadband oscillation risk of the alternating current-direct current hybrid system.
In a third aspect, the present invention also provides an electronic device, including: the system comprises a memory, a processor and a computer program stored in the memory and capable of running on the processor, wherein the processor realizes the identification method of the broadband oscillation risk of the alternating current-direct current series-parallel system when executing the computer program.
The invention provides a method and a device for identifying broadband oscillation risk of an alternating current-direct current series-parallel system, which at least comprise the following beneficial effects:
according to the method, key influence factors of broadband oscillation of the alternating current-direct current hybrid system are analyzed quantitatively through Copula entropy, so that key influence factors of broadband oscillation of the alternating current-direct current hybrid system are analyzed, and accurate and reliable basis is provided for subsequent oscillation inhibition through relevant methods such as targeted adjustment.
Additional features and advantages of the application will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the application. The objectives and other advantages of the application will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
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In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following description will briefly explain the drawings used in the embodiments or the description of the prior art, and it is obvious that the drawings in the following description are some embodiments of the present application, and other drawings can be obtained according to these drawings without inventive effort to a person skilled in the art.
FIG. 1 is a schematic flow chart of a method for identifying risk of broadband oscillation of an AC/DC hybrid system;
FIG. 2 is a flow chart illustrating the generation of an oscillation mode parameter matrix according to an embodiment of the present invention;
FIG. 3 is a schematic flow chart of performing parameter estimation on an oscillation influence factor matrix and an oscillation modal parameter matrix by using a Copula function according to an embodiment of the present invention to complete identification of broadband oscillation risk of an AC/DC hybrid system;
fig. 4 is a schematic diagram of an LCC receiver active power oscillation waveform according to an embodiment of the present invention;
fig. 5 is a schematic diagram of an LCC receiver active power oscillation spectrum according to an embodiment of the present invention;
fig. 6a, fig. 6b, and fig. 6c are schematic diagrams of the variation trend of the normalized influencing factors in the embodiments provided by the present invention;
Fig. 7 is a schematic structural diagram of an identification device for risk of broadband oscillation of an ac/dc hybrid system according to the present invention.
Detailed Description
In order to better understand the above technical solutions, the following detailed description will be given with reference to the accompanying drawings and specific embodiments. It will be apparent that the described embodiments are only some, but not all, embodiments of the invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
The terminology used in the embodiments of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used in this application and the appended claims, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise, the "plurality" generally includes at least two.
It should also be noted that the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a product 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 product or apparatus. Without further limitation, an element defined by the phrase "comprising one … …" does not exclude the presence of other like elements in a commodity or device comprising such element.
In order to reduce the damage of broadband oscillation, when the oscillation occurs, the key influencing factors of the oscillation need to be analyzed, so that the subsequent suppression of the oscillation by a relevant method such as targeted adjustment is facilitated.
The key influence factors of the broadband oscillation of the alternating current-direct current series-parallel system are analyzed in a quantitative mode through Copula entropy, and accurate and reliable basis is provided for the follow-up oscillation suppression through relevant methods such as targeted adjustment.
As shown in fig. 1, the invention provides a method for identifying broadband oscillation risk of an ac/dc series-parallel system, which specifically comprises the following steps:
acquiring a broadband oscillation quantitative evaluation index, generating an oscillation influence factor matrix based on the broadband oscillation quantitative evaluation index, and carrying out normalization processing;
based on the oscillation influence factor matrix after normalization processing, generating an oscillation mode parameter matrix by combining the division of frequency intervals;
and carrying out parameter estimation on the oscillation influence factor matrix and the oscillation modal parameter matrix through a Copula function to finish the identification of the broadband oscillation risk of the alternating current-direct current hybrid system.
Step 1, acquiring a broadband oscillation quantitative evaluation index, generating an oscillation influence factor matrix based on the broadband oscillation quantitative evaluation index, and carrying out normalization processing;
The factors which can represent the structure of the AC/DC series-parallel system and possibly cause oscillation comprise the output of a generator, the load of the AC/DC series-parallel system, the controller PI parameter of LCC or VSC, the phase-locked loop PI parameter and the like, N parameters are added, the size of the parameters is changed, and an N-order oscillation influence factor matrix is generated:
wherein P is G For the output of the generator, P L For the load capacity, k of an alternating current-direct current series-parallel system pi And k ii Current loop scaling and integration coefficients, k, for LCC or VSC pv And k iv The voltage loop ratio coefficient and integral coefficient, k, for LCC or VSC p And k i Is a phase-locked loop proportional coefficient and an integral coefficient.
And carrying out normalization processing on each column in the oscillation influence factor matrix, wherein a normalized calculation formula is as follows:
wherein X is ij Is the ith row and jth column element,is the normalized value of the ith row and jth column element, X jmin Is the j-th column element X j Minimum value of X jmax Is the j-th column element X j Is a maximum value of (a).
Step 2, generating an oscillation modal parameter matrix based on the oscillation influence factor matrix after normalization processing and combining the division of the frequency interval;
under the condition that the oscillation influencing factors change randomly, the impedance frequency characteristic of the system is obtained through an impedance measurement method under a synchronous coordinate system, so that parameter indexes of an oscillation mode, including frequency and damping, are obtained.
As shown in fig. 2, the steps specifically include:
step 201, dividing a frequency interval to obtain a plurality of sub-frequency intervals;
in the above step, the frequency interval of the full frequency band is divided into a plurality of sub-frequency intervals, and the identification error of the sub-frequency intervals needs to be within a preset threshold range.
In practical application, the ac-dc series-parallel system generally does not contain multiple zero points, i.e. the number of zero points is less than or equal to 2, and the frequency difference between the zero points is larger. On the premise that the sub-frequency interval cannot be taken too small, otherwise, the available data points are reduced, so that the identification error is increased, the number of the identified intervals is increased, and the calculated amount is increased; the sub-frequency interval cannot be too large, otherwise the sub-frequency interval [ f Lk ，f Uk ]There will be more than two zeros in.
In the above steps, the sub-frequency intervals are divided in a linear or logarithmic equal width manner according to the actual situation, and the identification error of the sub-frequency interval is used to determine whether the sub-frequency interval is suitable or not r Calculated by the following formula:
wherein e r H (jω) is the identification error of the sub-frequency interval i ) Is the actual value of the frequency response of the sub-frequency interval, H mea (jω i ) And n is the number of data points adopted by the sub-frequency interval.
When the error e is identified r If the frequency range is smaller than the preset threshold, the selected sub-frequency range is considered to be satisfactory, and the error e is identified r When the frequency exceeds the preset threshold, the selected sub-frequency interval is considered to be not satisfactory, at the moment, the selected sub-frequency interval can be divided into two parts, and the identification solution is re-carried out in the sub-frequency interval until the identification error e r Within a preset threshold.
Step 202, applying voltage step disturbance with preset frequency at a concerned node, obtaining a voltage disturbance response signal and a current disturbance response signal, and giving an impedance characteristic matrix of an alternating current-direct current series-parallel system, wherein the preset frequency is determined by each sub-frequency interval;
in the above step, d-axis voltage disturbance and q-axis voltage disturbance with specified frequencies are respectively and independently injected at the concerned node, and then two groups of voltage-current response signals are obtained through measurement, and the system impedance characteristic matrix is obtained through calculation by using the variation quantity of the voltage-current response signals, wherein the calculation formula is as follows:
wherein Z is total (s) is an impedance characteristic matrix of an alternating current-direct current series-parallel system, and Deltau d1 、△u q1 For the d-axis and q-axis voltage disturbance response signals when the d-axis disturbance is injected alone, deltai d1 、Δi q1 For d-axis and q-axis current disturbance response signals when d-axis disturbance is injected alone, deltau d2 、△u q2 For the d-axis and q-axis voltage disturbance response signals when the q-axis disturbance is injected alone, Δi d2 、Δi q2 For injecting the d-axis and q-axis current disturbance response signals when the q-axis disturbance is injected alone, Z dd 、Z dq 、Z qd 、Z qq Is Z total Four elements in(s).
Wherein the d-axis is the direction axis of the motor magnetic field and the q-axis is the direction axis of the motor rotor.
Step 203, analyzing determinant zero points of an impedance characteristic matrix of the alternating current-direct current series-parallel system, determining oscillation modes of the alternating current-direct current series-parallel system in each sub-frequency interval according to the determinant zero points, and obtaining corresponding damping;
the impedance is a stability criterion commonly used in the process of vibration risk assessment and identification, and the specific forms of the impedance comprise Nyquist criterion, norm criterion, bode diagram criterion, determinant zero criterion and the like. The determinant zero point criterion is the most accurate and visual criterion in the above forms, because it can not only give qualitative stable results, but also give quantitative stable indexes, so in the invention, the stability criterion of the impedance is determined by identifying the zero point of the determinant of the impedance, and is used for subsequent broadband oscillation risk assessment and identification.
Determinant calculation is carried out on an impedance characteristic matrix of the alternating current-direct current series-parallel system, and the determinant calculation is specifically expressed as follows:
det(Z total )＝Z dd Z qq -Z dq Z qd
Wherein det () is a determinant calculation function;
and obtaining determinant zero points of the impedance characteristic matrix of the alternating current-direct current hybrid system by analyzing determinant calculation results of the impedance characteristic matrix of the alternating current-direct current hybrid system.
By varying the frequency of the injected disturbance, an impedance determinant of the full frequency band is obtained and the full frequency band is divided into a plurality of sub-frequency bins, e.g. m sub-frequency bins. In a sub-frequency interval [ f Lk ，f Uk ]Obtaining the frequency response characteristic of the impedance determinant, namely H(s), by adopting a curve fitting method;
wherein f Lk Is the lower frequency limit of the kth sub-frequency interval, f Uk Is the upper frequency limit of the kth sub-frequency interval. The frequency response characteristic H(s) of the impedance determinant is calculated as follows:
wherein a is k 、b k The first-order coefficients of the denominator and the numerator are respectively obtained, the oscillation mode of the system in the sub-frequency interval can be obtained by solving the zero point of the system, and the damping zeta of the system can be obtained k 。
According to the method, oscillation modes in a plurality of sub-frequency intervals are calculated, and corresponding damping is obtained.
And 204, carrying out normalization processing on damping in each sub-frequency interval to construct an oscillation mode parameter matrix.
In the above steps, the damping obtained in N operating states is normalized to obtain a group of damping variables in the sub-frequency interval as a parameter matrix of the oscillation mode
And 3, carrying out parameter estimation on the oscillation influence factor matrix and the oscillation modal parameter matrix through a Copula function to finish identification of broadband oscillation risk of the alternating current-direct current hybrid system.
In the above steps, performing correlation analysis on two sets of random variables of the oscillation influencing factor and the oscillation parameter index can provide data support for broadband oscillation risk assessment, as shown in fig. 3, specifically including:
step 301, estimating parameters of random variables in the oscillation influence factor matrix and the oscillation modal parameter matrix, and calculating Copula entropy of each influence factor variable and damping variable in each sub-frequency interval according to the obtained Copula density functionThe calculation formula of Copula entropy is as follows:
where H () is the Copula entropy, c () is the Copula density function,normalized value for the j-th column influence factor variable, < ->Normalized value of damping variable for kth subfrequency interval,/>Normalized value of the factor variable in the j-th column in the i-th operating state, +.>And N is the total number of the running states, wherein the normalized value is the damping variable of the kth subfrequency section in the ith running state.
From this, copula entropy of each influencing factor variable and damping variable in each sub-frequency interval can be calculated:
Wherein H is cjk The Copula entropy of damping variables in the jth influencing factor variable and the kth subfrequency interval is n random variables in total, and m subfrequency intervals in total.
Step 302, in each sub-frequency interval, sorting random variables in the oscillation influence factor matrix according to the Copula entropy, determining key influence factors of broadband oscillation of the system according to sorting results, and performing broadband oscillation risk assessment and identification according to the key factors.
In the above steps, in each sub-frequency interval, the influence factor variables are ordered according to the Copula entropy, and the larger the Copula entropy is, the larger the influence of the corresponding variable on oscillation in the frequency band is, so that the key influence factor of the system broadband oscillation risk can be determined, and risk assessment can be performed.
According to the scheme, a provincial power grid is selected for experimental analysis, and an LCC simplified model is adopted for the provincial power grid, so that in order to analyze the oscillation risk of the system under small disturbance, a short voltage step disturbance is applied to a position with a large XX of a falling point of a receiving end of the LCC at a certain moment of stable operation of the system, the disturbance amplitude is 5% of rated voltage, the duration is 0.5 seconds, and the active power oscillation waveform of the large XX of the receiving end of the LCC after disturbance is cleared is shown in figure 4. The frequency spectrum analysis is carried out on the active power oscillation waveform of the receiving end, the frequency spectrum characteristics of the oscillation waveform are shown in figure 5, and the oscillation mode of about 9Hz can be determined from the figure. And carrying out parameter identification on the mode to obtain the mode frequency of 9.458Hz and the damping of 0.045, and carrying out key influence factor analysis based on Copula entropy by using the mode.
Possible influencing factors of LCC oscillation include various control parameters of an LCC rectifier and an inverter, transmission power of a direct current line, active power of a load and the like, so that correlation analysis based on Copula entropy is carried out on the factors respectively, and key influencing factors are extracted.
(1) Load and transmission power are unchanged, and influence of control parameters of the rectification side and the inversion side of the LCC is considered: the LCC rectifying side is provided with a PI controller, the inverting side is provided with two PI controllers, six control parameters are added, after all the control parameters are normalized, copula entropy of damping is calculated respectively, and the result is shown in the following table:
from the table, it can be seen that the integral coefficient K of the LCC rectifier ire The damping Copula entropy is the largest, so that the damping Copula entropy is a key control parameter of the oscillation mode, and the rest control parameters and the damping Copula entropy are small negative numbers and can be regarded as 0, so that the damping Copula entropy has little correlation with the oscillation mode.
(2) The LCC control parameters are unchanged, and the influence of load and direct current transmission power nearby the LCC is considered: because the two falling points of the LCC are in the high XX and the large XX, several similar loads are selected for comparison with the direct current transmission power, and curves of random changes of the normalized load power, the direct current transmission power and the oscillation damping are respectively drawn, as shown in fig. 6a, 6b and 6 c. The direct current transmission power and the change of the oscillation damping are kept highly consistent, and have strong correlation, and no obvious correlation exists between other load powers and the change of the oscillation damping. The calculation results of Copula entropy are shown in the following table:
It can be seen from the table that the dc transmission power and damping Copula entropy are large, and therefore are key influencing factors of the oscillation mode. The Copula entropy of each load and damping is a small negative number, which can be seen as 0, and therefore has little correlation with the oscillation mode.
(3) The LCC control parameters and the direct current transmission power are unchanged, and the influence of loads of different sizes and different positions is considered: and (3) grading all loads in the provincial power grid LCC simplified model according to the size and distance from the LCC, and calculating Copula entropy of each load and damping, wherein the Copula entropy is shown in the following table:
it can be seen from the above table that the greater the load has a greater effect on the oscillation mode when the load is located close to the LCC, but this is not the case when the load is too far from the LCC; secondly, when the load is close in size, the load at different positions has no obvious influence on the oscillation mode.
In summary, the method and the device are based on quantitative analysis of the key influence factors of the broadband oscillation of the Copula entropy, so that the key influence factors of the broadband oscillation of the alternating-current and direct-current series-parallel system are analyzed, and accurate and reliable basis is provided for the follow-up oscillation suppression through relevant methods such as targeted adjustment. Experimental analysis can show that the scheme can effectively reduce system power fluctuation, reduce the harm of broadband oscillation, avoid occurrence of grid interlocking accidents and ensure safe and stable operation of the power system.
As shown in fig. 7, the present invention further provides a device for identifying a risk of broadband oscillation of an ac/dc hybrid system, which adopts the method for identifying a risk of broadband oscillation of an ac/dc hybrid system as described above, and specifically includes:
the oscillation influence factor matrix generation module is used for acquiring broadband oscillation quantitative evaluation indexes, generating an oscillation influence factor matrix based on the broadband oscillation quantitative evaluation indexes, and carrying out normalization processing;
the oscillation modal parameter matrix generation module is used for generating an oscillation modal parameter matrix based on the oscillation influence factor matrix after normalization processing and combining the division of the frequency interval;
and the broadband oscillation risk assessment module is used for carrying out parameter estimation on the oscillation influence factor matrix and the oscillation modal parameter matrix through the Copula function so as to complete identification of broadband oscillation risk of the alternating current-direct current hybrid system.
Further, the wideband oscillation quantization evaluation index includes a generator output, a load of an ac-dc series-parallel system, a controller PI parameter of the LCC and/or the VSC, and a phase-locked loop PI parameter.
Further, the normalization process includes: normalizing each column in the oscillation influence factor matrix, specifically expressed as:
wherein X is ij Is the ith row and jth column element, Is the normalized value of the ith row and jth column element, X jmin Is the j-th column element X j Minimum value of X jmax Is the j-th column element X j Is a maximum value of (a).
Further, based on the oscillation influence factor matrix after normalization processing, and in combination with the division of the frequency interval, an oscillation mode parameter matrix is generated, which specifically comprises the following steps:
dividing the frequency interval to obtain a plurality of sub-frequency intervals;
applying voltage step disturbance of preset frequency at the concerned node, obtaining a voltage disturbance response signal and a current disturbance response signal, and giving an impedance characteristic matrix of the alternating current-direct current series-parallel system, wherein the preset frequency is determined by each sub-frequency interval;
analyzing determinant zero points of an impedance characteristic matrix of the alternating current-direct current series-parallel system, determining oscillation modes of the alternating current-direct current series-parallel system in each sub-frequency interval according to the determinant zero points, and obtaining corresponding damping;
and carrying out normalization processing on damping in each sub-frequency interval to construct an oscillation modal parameter matrix.
Further, the frequency interval is divided to obtain a plurality of sub-frequency intervals, which specifically includes:
dividing the frequency interval in a linear equal width or logarithmic equal width mode to obtain a plurality of sub-frequency intervals, wherein the identification error of each sub-frequency interval is within a preset threshold range.
Further, the identification error of each sub-frequency interval is within a preset threshold range, which specifically includes: comparing the identification error with a preset threshold range, and confirming that the identification error is within the preset threshold by performing bipartite and re-identification solving on the sub-frequency interval.
Further, the identification error of the sub-frequency interval is specifically expressed as:
wherein e r H (jω) is the identification error of the sub-frequency interval i ) Is the actual value of the frequency response of the sub-frequency interval, H mea (jω i ) And n is the number of data points adopted by the sub-frequency interval.
Further, applying a voltage step disturbance of a preset frequency at the node of interest specifically includes: d-axis and q-axis voltage disturbances of a preset frequency are injected separately at the node of interest.
Further, the impedance characteristic matrix of the ac/dc series-parallel system is specifically expressed as:
wherein Z is total (s) is an impedance characteristic matrix of an alternating current-direct current series-parallel system, and Deltau d1 、△u q1 For the d-axis and q-axis voltage disturbance response signals when the d-axis disturbance is injected alone, deltai d1 、Δi q1 For d-axis and q-axis current disturbance response signals when d-axis disturbance is injected alone, deltau d2 、△u q2 For d-axis, q-axis voltage disturbances when q-axis disturbances are injected aloneResponse signal Δi d2 、Δi q2 For injecting the d-axis and q-axis current disturbance response signals when the q-axis disturbance is injected alone, Z dd 、Z dq 、Z qd 、Z qq Is Z total Four elements in(s).
Further, analyzing determinant zero points of an impedance characteristic matrix of the alternating current-direct current series-parallel system specifically comprises the following steps:
determinant calculation is carried out on an impedance characteristic matrix of the alternating current-direct current series-parallel system, and the determinant calculation is specifically expressed as follows:
det(Z total )＝Z dd Z qq -Z dq Z qd
wherein det () is a determinant calculation function;
and obtaining determinant zero points of the impedance characteristic matrix of the alternating current-direct current hybrid system by analyzing determinant calculation results of the impedance characteristic matrix of the alternating current-direct current hybrid system.
Further, parameter estimation is carried out on the oscillation influence factor matrix and the oscillation modal parameter matrix through a Copula function, so that the identification of the broadband oscillation risk of the alternating current-direct current series-parallel system is completed, and the method specifically comprises the following steps:
carrying out parameter estimation on random variables in the oscillation influence factor matrix and the oscillation modal parameter matrix through the C0pula function to obtain a Copula density function, and analyzing Copula entropy of influence factor variables and damping variables in each sub-frequency interval;
according to the Copula entropy obtained by analysis, the random variables in the oscillation influence factor matrix are ordered, key influence factors of the broadband oscillation of the system are determined based on the ordering result, and the broadband oscillation risk identification is carried out according to the key factors.
Further, copula entropy of influencing factor variables and damping variables in each sub-frequency interval is analyzed, and the Copula entropy is specifically expressed as:
where H () is the Copula entropy, c () is the Copula density function,normalized value for the j-th column influence factor variable, < ->Normalized value of damping variable for kth subfrequency interval,/>Normalized value of the factor variable in the j-th column in the i-th operating state, +.>And N is the total number of the running states, wherein the normalized value is the damping variable of the kth subfrequency section in the ith running state.
Further, the larger the Copula entropy value, the higher the risk of oscillation corresponding to the preset frequency.
The invention provides a method and a device for identifying broadband oscillation risk of an alternating current-direct current series-parallel system, which at least comprise the following beneficial effects:
according to the method, key influence factors of broadband oscillation of the alternating current-direct current hybrid system are analyzed quantitatively through Copula entropy, so that key influence factors of broadband oscillation of the alternating current-direct current hybrid system are analyzed, and accurate and reliable basis is provided for subsequent oscillation inhibition through relevant methods such as targeted adjustment.
In addition, the invention also provides computer equipment.
In an exemplary embodiment, the apparatus includes: one or more processors and memory, for example, a single processor and memory. The processor and the memory may be connected by a bus or other means.
The memory, as a non-transitory computer readable storage medium, may be configured to store a non-transitory software program and a non-transitory computer executable program, as in the data processing method in the embodiment of the application, that is, a method for identifying a broadband oscillation risk of an ac/dc hybrid system, specifically includes the following steps:
acquiring a broadband oscillation quantitative evaluation index, generating an oscillation influence factor matrix based on the broadband oscillation quantitative evaluation index, and carrying out normalization processing;
based on the oscillation influence factor matrix after normalization processing, generating an oscillation mode parameter matrix by combining the division of frequency intervals;
and carrying out parameter estimation on the oscillation influence factor matrix and the oscillation modal parameter matrix through a Copula function to finish the identification of the broadband oscillation risk of the alternating current-direct current hybrid system.
According to the method, key influence factors of broadband oscillation of the alternating current-direct current hybrid system are analyzed quantitatively through Copula entropy, so that key influence factors of broadband oscillation of the alternating current-direct current hybrid system are analyzed, and accurate and reliable basis is provided for subsequent oscillation inhibition through relevant methods such as targeted adjustment.
Further, the wideband oscillation quantization evaluation index includes a generator output, a load of an ac-dc series-parallel system, a controller PI parameter of the LCC and/or the VSC, and a phase-locked loop PI parameter.
Further, the normalization process includes: normalizing each column in the oscillation influence factor matrix, specifically expressed as:
wherein X is ij Is the ith row and jth column element,is the normalized value of the ith row and jth column element, X jmin Is the j-th column element X j Minimum value of X jmax Is the j-th column element X j Is a maximum value of (a).
Further, based on the oscillation influence factor matrix after normalization processing, and in combination with the division of the frequency interval, an oscillation mode parameter matrix is generated, which specifically comprises the following steps:
dividing the frequency interval to obtain a plurality of sub-frequency intervals;
applying voltage step disturbance of preset frequency at the concerned node, obtaining a voltage disturbance response signal and a current disturbance response signal, and giving an impedance characteristic matrix of the alternating current-direct current series-parallel system, wherein the preset frequency is determined by each sub-frequency interval;
analyzing determinant zero points of an impedance characteristic matrix of the alternating current-direct current series-parallel system, determining oscillation modes of the alternating current-direct current series-parallel system in each sub-frequency interval according to the determinant zero points, and obtaining corresponding damping;
and carrying out normalization processing on damping in each sub-frequency interval to construct an oscillation modal parameter matrix.
Further, the frequency interval is divided to obtain a plurality of sub-frequency intervals, which specifically includes:
Dividing the frequency interval in a linear equal width or logarithmic equal width mode to obtain a plurality of sub-frequency intervals, wherein the identification error of each sub-frequency interval is within a preset threshold range.
Further, the identification error of each sub-frequency interval is within a preset threshold range, which specifically includes: comparing the identification error with a preset threshold range, and confirming that the identification error is within the preset threshold by performing bipartite and re-identification solving on the sub-frequency interval.
Further, the identification error of the sub-frequency interval is specifically expressed as:
wherein e r H (jω) is the identification error of the sub-frequency interval i ) Is the actual value of the frequency response of the sub-frequency interval, H mea (jω i ) And n is the number of data points adopted by the sub-frequency interval.
Further, applying a voltage step disturbance of a preset frequency at the node of interest specifically includes: d-axis and q-axis voltage disturbances of a preset frequency are injected separately at the node of interest.
Further, the impedance characteristic matrix of the ac/dc series-parallel system is specifically expressed as:
wherein Z is total (s) is an impedance characteristic matrix of an alternating current-direct current series-parallel system, and Deltau d1 、△u q1 For the d-axis and q-axis voltage disturbance response signals when the d-axis disturbance is injected alone, deltai d1 、Δi q1 For d-axis and q-axis current disturbance response signals when d-axis disturbance is injected alone, deltau d2 、△u q2 For the d-axis and q-axis voltage disturbance response signals when the q-axis disturbance is injected alone, Δi d2 、Δi q2 For injecting the d-axis and q-axis current disturbance response signals when the q-axis disturbance is injected alone, Z dd 、Z dq 、Z qd 、Z qq Is Z total Four elements in(s).
Further, analyzing determinant zero points of an impedance characteristic matrix of the alternating current-direct current series-parallel system specifically comprises the following steps:
determinant calculation is carried out on an impedance characteristic matrix of the alternating current-direct current series-parallel system, and the determinant calculation is specifically expressed as follows:
det(Z total )＝Z dd Z qq -Z dq Z qd
wherein det () is a determinant calculation function;
and obtaining determinant zero points of the impedance characteristic matrix of the alternating current-direct current hybrid system by analyzing determinant calculation results of the impedance characteristic matrix of the alternating current-direct current hybrid system.
Further, parameter estimation is carried out on the oscillation influence factor matrix and the oscillation modal parameter matrix through a Copula function, so that the identification of the broadband oscillation risk of the alternating current-direct current series-parallel system is completed, and the method specifically comprises the following steps:
carrying out parameter estimation on random variables in the oscillation influence factor matrix and the oscillation modal parameter matrix through the Copula function to obtain a Copula density function, and analyzing Copula entropy of influence factor variables and damping variables in each sub-frequency interval;
According to the Copula entropy obtained by analysis, the random variables in the oscillation influence factor matrix are ordered, key influence factors of the broadband oscillation of the system are determined based on the ordering result, and the broadband oscillation risk identification is carried out according to the key factors.
Further, copula entropy of influencing factor variables and damping variables in each sub-frequency interval is analyzed, and the Copula entropy is specifically expressed as:
where H () is the Copula entropy, c () is the Copula density function,normalized value for the j-th column influence factor variable, < ->Normalized value of damping variable for kth subfrequency interval,/>Normalized value of the factor variable in the j-th column in the i-th operating state, +.>And N is the total number of the running states, wherein the normalized value is the damping variable of the kth subfrequency section in the ith running state.
Further, the larger the Copula entropy value, the higher the risk of oscillation corresponding to the preset frequency.
The processor implements the data processing method in the embodiments of the present application described above by running a non-transitory software program stored in a memory, as well as the program.
The memory may include a memory program area and a memory data area, wherein the memory program area may store an operating system, at least one application program required for a function; the storage data area may store data and the like required to perform the data processing method in the embodiment of the present application described above. In addition, the memory may include high-speed random access memory, and may also include non-transitory memory, such as at least one magnetic disk storage device, flash memory device, or other non-transitory solid state storage device. In some embodiments, the memory may include memory remotely located with respect to the processor, which may be connected to the data processing apparatus via a network. Examples of such networks include, but are not limited to, the internet, intranets, local area networks, mobile communication networks, and combinations thereof.
Those of ordinary skill in the art will appreciate that all or some of the steps, systems, and methods disclosed above may be implemented as software, firmware, hardware, and suitable combinations thereof. Some or all of the physical components may be implemented as software executed by a processor, such as a central processing unit, digital signal processor, or microprocessor, or as hardware, or as an integrated circuit, such as an application specific integrated circuit. Such software may be distributed on computer readable media, which may include computer storage media (or non-transitory media) and communication media (or transitory media). The term computer storage media includes both volatile and nonvolatile, removable and non-removable media implemented in any method or technology for storage of information such as computer readable programs, data structures, program modules or other data, as known to those skilled in the art. Computer storage media includes, but is not limited to, RAM, ROM, EEPROM, flash memory or other memory technology, CD-ROM, digital Versatile Disks (DVD) or other optical disk storage, magnetic cassettes, magnetic tape, magnetic disk storage or other magnetic storage devices, or any other medium which can be used to store the desired information and which can be accessed by a computer. Furthermore, as is well known to those of ordinary skill in the art, communication media typically embodies computer readable programs, data structures, program modules or other data in a modulated data signal such as a carrier wave or other transport mechanism and includes any information delivery media.
While preferred embodiments of the present invention have been described, additional variations and modifications in those embodiments may occur to those skilled in the art once they learn of the basic inventive concepts. It is therefore intended that the following claims be interpreted as including the preferred embodiments and all such alterations and modifications as fall within the scope of the invention. It will be apparent to those skilled in the art that various modifications and variations can be made to the present invention without departing from the spirit or scope of the invention. Thus, it is intended that the present invention also include such modifications and alterations insofar as they come within the scope of the appended claims or the equivalents thereof.
Claims (15)
1. A method for identifying broadband oscillation risk of an alternating current-direct current series-parallel system is characterized by comprising the following steps:
acquiring a broadband oscillation quantitative evaluation index, generating an oscillation influence factor matrix based on the broadband oscillation quantitative evaluation index, and carrying out normalization processing;
based on the oscillation influence factor matrix after normalization processing, generating an oscillation mode parameter matrix by combining the division of frequency intervals;
and carrying out parameter estimation on the oscillation influence factor matrix and the oscillation modal parameter matrix through a Copula function to finish the identification of the broadband oscillation risk of the alternating current-direct current hybrid system.
2. The method of claim 1, wherein the quantitative evaluation index of the wideband oscillation includes a generator output, a load of the ac-dc hybrid system, a controller PI parameter of the LCC and/or the VSC, and a phase-locked loop PI parameter.
3. The method for identifying broadband oscillation risk of an ac/dc series-parallel system according to claim 1, wherein the normalization process comprises: normalizing each column in the oscillation influence factor matrix, specifically expressed as:
wherein X is ij Is the ith row and jth column element,is the normalized value of the ith row and jth column element, X jmin Is the j-th column element X j Minimum value of X jmax Is the j-th column element X j Is a maximum value of (a).
4. The method for identifying broadband oscillation risk of an ac/dc series-parallel system according to claim 1, wherein the method for identifying broadband oscillation risk of the ac/dc series-parallel system is characterized by generating an oscillation mode parameter matrix based on the oscillation influence factor matrix after normalization processing and by combining frequency interval division, and specifically comprises the following steps:
dividing the frequency interval to obtain a plurality of sub-frequency intervals;
applying voltage step disturbance of preset frequency at the concerned node, obtaining a voltage disturbance response signal and a current disturbance response signal, and giving an impedance characteristic matrix of the alternating current-direct current series-parallel system, wherein the preset frequency is determined by each sub-frequency interval;
Analyzing determinant zero points of an impedance characteristic matrix of the alternating current-direct current series-parallel system, determining oscillation modes of the alternating current-direct current series-parallel system in each sub-frequency interval according to the determinant zero points, and obtaining corresponding damping;
and carrying out normalization processing on damping in each sub-frequency interval to construct an oscillation modal parameter matrix.
5. The method for identifying broadband oscillation risk of an ac/dc hybrid system according to claim 4, wherein the frequency interval is divided to obtain a plurality of sub-frequency intervals, and the method specifically comprises:
dividing the frequency interval in a linear equal width or logarithmic equal width mode to obtain a plurality of sub-frequency intervals, wherein the identification error of each sub-frequency interval is within a preset threshold range.
6. The method for identifying risk of wideband oscillation in an ac/dc hybrid system according to claim 5, wherein the identification error of each sub-frequency interval is within a predetermined threshold range, specifically comprising: comparing the identification error with a preset threshold range, and confirming that the identification error is within the preset threshold by performing bipartite and re-identification solving on the sub-frequency interval.
7. The method for identifying risk of wideband oscillation of an ac/dc hybrid system according to claim 6, wherein the identification error of the sub-frequency interval is specifically expressed as:
Wherein e r H (jω) is the identification error of the sub-frequency interval i ) Is the actual value of the frequency response of the sub-frequency interval, H mea (jω i ) And n is the number of data points adopted by the sub-frequency interval.
8. The method for identifying risk of broadband oscillation of an ac/dc hybrid system according to claim 4, wherein applying a voltage step disturbance of a predetermined frequency at the node of interest comprises: d-axis and q-axis voltage disturbances of a preset frequency are injected separately at the node of interest.
9. The method for identifying broadband oscillation risk of an ac/dc hybrid system according to claim 8, wherein the impedance characteristic matrix of the ac/dc hybrid system is specifically expressed as:
wherein Z is total (s) is an impedance characteristic matrix of an alternating current-direct current series-parallel system, delta u d1 、Δu q1 For the d-axis and q-axis voltage disturbance response signals when the d-axis disturbance is injected alone, deltai d1 、Δi q1 For d-axis and q-axis current disturbance response signals when d-axis disturbance is injected alone, deltau d2 、Δu q2 For the d-axis and q-axis voltage disturbance response signals when the q-axis disturbance is injected alone, Δi d2 、Δi q2 For injecting the d-axis and q-axis current disturbance response signals when the q-axis disturbance is injected alone, Z dd 、Z dq 、Z qd 、Z qq Is Z total Four elements in(s).
10. The method for identifying broadband oscillation risk of an ac/dc hybrid system according to claim 9, wherein the analysis of determinant zero points of an impedance characteristic matrix of the ac/dc hybrid system specifically comprises the following steps:
Determinant calculation is carried out on an impedance characteristic matrix of the alternating current-direct current series-parallel system, and the determinant calculation is specifically expressed as follows:
set(Z total )＝Z dd Z qq -Z dq Z qd
wherein det () is a determinant calculation function;
and obtaining determinant zero points of the impedance characteristic matrix of the alternating current-direct current hybrid system by analyzing determinant calculation results of the impedance characteristic matrix of the alternating current-direct current hybrid system.
11. The method for identifying broadband oscillation risk of an alternating current-direct current hybrid system according to claim 1, wherein the identification of the broadband oscillation risk of the alternating current-direct current hybrid system is completed by performing parameter estimation on an oscillation influence factor matrix and an oscillation mode parameter matrix through a Copula function, and specifically comprises the following steps:
carrying out parameter estimation on random variables in the oscillation influence factor matrix and the oscillation modal parameter matrix through the Copula function to obtain a Copula density function, and analyzing Copula entropy of influence factor variables and damping variables in each sub-frequency interval;
according to the Copula entropy obtained by analysis, the random variables in the oscillation influence factor matrix are ordered, key influence factors of the broadband oscillation of the system are determined based on the ordering result, and the broadband oscillation risk identification is carried out according to the key factors.
12. The method for identifying broadband oscillation risk of an ac-dc series-parallel system according to claim 11, wherein the Copula entropy of the influencing factor variable and the damping variable in each sub-frequency interval is analyzed, specifically expressed as:
Where H () is the Copula entropy, c () is the Copula density function,normalized values for the j-th influencing factor variable,normalized value of damping variable for kth subfrequency interval,/>Normalized value of the factor variable in the j-th column in the i-th operating state, +.>And N is the total number of the running states, wherein the normalized value is the damping variable of the kth subfrequency section in the ith running state.
13. The method for identifying risk of wideband oscillation of an ac/dc hybrid system according to claim 11, wherein the larger the Copula entropy value is, the higher the risk of oscillation corresponding to the preset frequency is.
14. The identification device for the broadband oscillation risk of the alternating current-direct current hybrid system is characterized by adopting the identification method for the broadband oscillation risk of the alternating current-direct current hybrid system according to any one of claims 1-13, and specifically comprising the following steps:
the oscillation influence factor matrix generation module is used for acquiring broadband oscillation quantitative evaluation indexes, generating an oscillation influence factor matrix based on the broadband oscillation quantitative evaluation indexes, and carrying out normalization processing;
the oscillation modal parameter matrix generation module is used for generating an oscillation modal parameter matrix based on the oscillation influence factor matrix after normalization processing and combining the division of the frequency interval;
And the broadband oscillation risk assessment module is used for carrying out parameter estimation on the oscillation influence factor matrix and the oscillation modal parameter matrix through the Copula function so as to complete identification of broadband oscillation risk of the alternating current-direct current hybrid system.
15. An electronic device, comprising: the method for identifying the broadband oscillation risk of the alternating current-direct current series-parallel system comprises a memory, a processor and a computer program stored in the memory and capable of running on the processor, wherein the processor realizes the identification method for the broadband oscillation risk of the alternating current-direct current series-parallel system according to any one of claims 1 to 13 when executing the computer program.
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