CN115471045A - Comprehensive evaluation method for AGC frequency modulation performance of power grid - Google Patents
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Abstract
The invention discloses a comprehensive evaluation method for AGC frequency modulation performance of a power grid, belonging to the field of power grid frequency modulation; the evaluation method comprises the following steps: firstly, constructing an AGC frequency modulation performance comprehensive index system under step disturbance and an AGC frequency modulation performance comprehensive index system under continuous disturbance; determining the comprehensive evaluation result of the AGC frequency modulation performance of the power grid through non-dimensionalization processing, determining the comprehensive index weight based on a subjective and objective combination weighting method, constructing a TOPSIS-grey correlation degree model, and determining the comprehensive evaluation result of the AGC frequency modulation performance of the power grid, thereby constructing a comprehensive evaluation method of the AGC frequency modulation performance of the power grid based on the combination weighting-TOPSIS-grey correlation degree model; the difference of AGC frequency modulation instructions and the output characteristics of the frequency modulation power supply under different disturbance working conditions is fully considered, an evaluation index system is respectively constructed for the step disturbance working conditions and the continuous disturbance working conditions, each evaluation index is convenient to calculate, the discrimination degree of the frequency modulation performance is high, the advantages and the value of high-quality frequency modulation resources can be better embodied, and more high-quality resources are encouraged to be added into a frequency modulation auxiliary service market.
Description
Technical Field
The invention belongs to the field of power grid frequency modulation, and particularly relates to a comprehensive evaluation method for AGC (automatic gain control) frequency modulation performance of a power grid.
Background
With the continuous growth of the power generation scale of new energy, the problems of intermittent power generation, fluctuation and even inverse regulation are increasingly obvious, great challenges are brought to the safety and stability of a power system, and the problem of power grid frequency modulation also becomes a focus; automatic Generation Control (AGC) frequency modulation is an important means of frequency adjustment in power systems. At present, AGC frequency modulation power supplies and control modes are more in variety, and with the reduction of energy storage cost and the rapid development of energy storage technology, high-quality frequency modulation resources represented by energy storage batteries are gradually added into an AGC frequency modulation auxiliary service market; in order to better understand AGC frequency modulation performance of each frequency modulation power supply and different control modes, more high-quality resources are encouraged to be added into a frequency modulation auxiliary service market, and it is particularly important to establish a reasonable and effective comprehensive evaluation method for the AGC frequency modulation performance of the power grid.
At present, partial scholars develop researches on the problem of evaluation of the AGC frequency modulation performance of a power grid, and corresponding AGC frequency modulation performance evaluation indexes are formulated and issued in many areas at home and abroad; the current AGC frequency modulation performance evaluation indexes at home and abroad are different, but the regulation rate, the regulation precision, the response time and the like of the AGC frequency modulation power supply are essentially examined; the regulation rate and the regulation precision are two most main refinement indexes examined. The existing evaluation indexes are mainly formulated and evaluated aiming at the traditional unit, the standard reaching requirement is low, and the advantages and the value of novel high-quality frequency modulation resources cannot be fully embodied.
The power grid AGC frequency modulation performance assessment standard is generally composed of multiple indexes, and a single evaluation index cannot obtain a comprehensive and objective evaluation result; the comprehensive evaluation method based on multiple indexes comprises a close value method, an analytic hierarchy process, a factor analysis method, a grey correlation analysis method, a principal component analysis method and the like at present; the related scholars adopt a close value method to comprehensively evaluate the primary frequency modulation performance of the unit, but when multi-index weight is considered, a subjective weighting method of expert knowledge is adopted, so that the objectivity of an evaluation result is not facilitated; most of the existing researches only use a single certain method model for comprehensive evaluation, and have certain defects; in the aspect of power grid AGC frequency modulation, a corresponding evaluation mechanism is not formed at present to comprehensively evaluate the AGC frequency modulation performance.
Disclosure of Invention
Aiming at the defects of the prior art, the invention aims to provide a comprehensive evaluation method for the AGC frequency modulation performance of a power grid, which fully considers the difference between AGC frequency modulation instructions under different disturbance working conditions and the output characteristics of a frequency modulation power supply, respectively constructs an evaluation index system for step and continuous disturbance working conditions, is convenient to calculate each evaluation index, has higher discrimination on the frequency modulation performance, can embody the advantages and the value of high-quality frequency modulation resources, and encourages more high-quality resources to be added into a frequency modulation auxiliary service market.
The purpose of the invention can be realized by the following technical scheme:
a comprehensive evaluation method for AGC frequency modulation performance of a power grid comprises the following steps:
s1, constructing an AGC frequency modulation performance comprehensive index system under step disturbance and an AGC frequency modulation performance comprehensive index system under continuous disturbance;
s2, constructing a comprehensive evaluation method of the AGC frequency modulation performance of the power grid based on a combined weighting-TOPSIS-grey correlation degree model; the method specifically comprises the following steps:
s21, carrying out dimensionless processing;
s22, determining index comprehensive weight based on a subjective and objective combination weighting method;
s23, constructing a TOPSIS-grey correlation degree model, and determining a comprehensive evaluation result of the AGC frequency modulation performance of the power grid;
in S1, an AGC frequency modulation performance comprehensive index system under step disturbance comprises three indexes of regulation rate, regulation precision and response time related to output, and six indexes of maximum frequency deviation, steady-state frequency deviation, frequency fluctuation rate, frequency recovery rate, frequency deviation degree and frequency recovery time related to frequency;
the AGC frequency modulation performance comprehensive index system under continuous disturbance comprises three indexes of regulation rate, regulation precision and response time related to output and a frequency deviation index related to frequency.
Further, the calculation expressions of three indexes related to output in the AGC frequency modulation performance comprehensive index system under step disturbance are respectively as follows:
1) Adjusting the rate index:
in the formula, v represents the regulation rate of the frequency modulation power supply during AGC regulation; p e Indicating the output of the frequency modulation power supply at the end of the adjustment; p s Indicating the output of the frequency-modulated power supply at the beginning of the regulation; t is a unit of e Representing the end time of the climbing section when AGC is adjusted; t is s Representing the starting time of the climbing section when AGC is adjusted; k 1 Representing an AGC regulation rate index of the frequency modulation power supply; v. of N Indicating a standard rate of adjustment;
2) Adjusting precision indexes:
in the formula, P bias The deviation amount is averagely adjusted during adjustment; p A The AGC command power is adjusted; p (t) is the output of the frequency modulation power supply in the oscillation time period during adjustment; t is oc The time length of the oscillation time period during adjustment; k 2 Showing AGC adjusting precision index of the frequency modulation power supply; p N,bias To representAdjusting a standard value of the deviation amount;
3) Response time index:
in the formula, K 3 Representing an AGC response time index of the frequency modulation power supply; t represents the response time when the frequency modulation power supply is adjusted; t is t N Indicating the standard response time.
Further, under step disturbance, the calculation expressions of six indexes related to the frequency in the AGC frequency modulation performance comprehensive index system are respectively as follows:
1) Maximum frequency deviation index:
in the formula, D m Is the maximum frequency deviation index; d m Is the maximum value of the absolute value of the frequency deviation; d N,m Adjusting multiple for increasing the maximum frequency deviation index discrimination;
2) Steady state frequency deviation index:
in the formula, ds is a steady-state frequency deviation index; d s Is a steady state frequency deviation value; d is a radical of N,s Adjusting multiple for increasing steady state frequency deviation index differentiation;
3) Frequency fluctuation rate index:
in the formula (I), the compound is shown in the specification,v m representing the rate of frequency fluctuation; d is a radical of m Is the maximum value of the absolute value of the frequency deviation; t is t m Indicating the time at which the absolute value of the maximum frequency deviation occurs; t is t b Indicating the adjustment start time; v m Is a frequency fluctuation rate index; v. of N,m Adjusting multiple for increasing frequency fluctuation rate index differentiation;
4) Frequency recovery rate index:
in the formula, v r Represents a frequency recovery rate; d m Is the maximum value of the absolute value of the frequency deviation; d s Is a steady state frequency offset value); t is t s Representing the time when the steady-state frequency deviation value occurs; t is t m Indicating the moment when the absolute value of the maximum frequency deviation occurs; v r Is a frequency recovery rate indicator; v. of N,r Is an adjustment multiple for increasing the frequency recovery rate index discrimination;
5) Frequency deviation index:
in the formula, σ 1 Representing the overall standard deviation of the frequency of the whole adjusting process; n is s Numbering sampling points when the steady-state frequency is reached; f. of i Representing the system frequency corresponding to the ith sampling point; f. of N Represents a reference frequency; d d Is a frequency deviation index; sigma 1N Adjusting multiple for increasing frequency deviation index differentiation;
6) Frequency recovery time index:
t r ＝t s -t b (14)
in the formula, t r Represents a frequency recovery duration(s); t is t s Represents the time at which the steady state frequency occurs; t is t b Indicating the adjustment start time; t is r Is a frequency recovery time index; t is t N,r A standard value representing the frequency recovery period.
Further, under continuous disturbance, three indexes related to output in an AGC frequency modulation performance comprehensive index system are calculated according to the following expressions:
1) Adjusting the rate index:
in the formula, v 1 (t) the output regulation rate of the frequency modulation power supply responding to the AGC instruction issued at the t moment; p (t) is the actual output at the moment t; v. of 2 (t) is the AGC command rate of change (; P) agc (t) an AGC command value issued at the moment t; d a (t) is the variation of two adjacent AGC commands; m is a group of 1 D is a judgment factor for regulating the rate index;
2) Adjusting precision indexes:
m a (t)＝|P agc (t)-P(t+T)| (18)
in the formula, m a (t) the final output response deviation of the frequency modulation power supply to the AGC command issued at the time t; p is agc When (t) is tAn AGC instruction value is issued at every moment; p (t) is the actual output at the moment t; m is a group of 2 To adjust the accuracy index, m N,a (t) is the output response deviation threshold;
3) Response time index:
in the formula, C n Is a sequence { P agc And { P } and n a correlation coefficient of } is calculated; t is a unit of d A response delay time(s); delta t is sampling interval time(s), and 10s is taken in the invention; i is the sampling point serial number corresponding to the response moment; p is the sequence { C n The sequence number of the sampling point corresponding to the maximum element in the sequence is obtained; q is the sequence { C n The first of which is larger than C N The sampling point sequence number corresponding to the element of (1); c q Is a sequence { C n The first of which is larger than C N The element (b); c N Is a correlation coefficient reference value; m is a group of 3 M is the number of sampling points as a response time index.
Further, in an AGC frequency modulation performance comprehensive index system under continuous disturbance, a calculation expression of a frequency deviation index related to frequency is as follows:
in the formula, σ 2 Representing the frequency overall variance (Hz) over the time period; n is z Is when it isThe number of the last sampling point in the segment; f. of i Representing the system frequency (Hz) corresponding to the ith sampling point; f. of N Represents a reference frequency; f d As an index of frequency deviation σ 2N Is an adjustment multiple for increasing the frequency deviation index discrimination.
Further, the formula for non-dimensionalizing the data in S21 is:
in the formula, x ij The original value of the jth evaluation index of the ith object to be evaluated is obtained; y is ij Is x ij The values after dimensionless processing.
Further, in the S22, an entropy weight method in the objective weighting method calculates objective weights of the AGC frequency modulation performance indicators, and the calculation formula is as follows:
(1) and (3) carrying out standardization processing on each index, wherein the calculation formula is as follows:
in the formula, c ij The index value is the index value after the j item evaluation index of the ith object to be evaluated is standardized;
(2) calculating entropy values of indexes, wherein the calculation formula is as follows:
in the formula, e j Entropy value of j-th evaluation index;
(3) determining the objective weight of each index, and calculating the formula as follows:
in the formula, w k j Is as followsAnd j are objective weights of the evaluation indexes.
Further, in S22, the calculation step of the subjective-objective combination weighting algorithm is as follows:
(1) constructing an optimization decision model, and integrating the weight calculation formula as follows:
in the formula, w j The comprehensive weight of the jth evaluation index; w is a z j The subjective weight of the jth evaluation index; alpha is alpha 1 And beta 1 Preference degree coefficients respectively representing subjective and objective weights;
(2) introducing Euclidean distance function d (w) z j ，w k j ) The difference degree relation equation between the subjective and objective weights and the corresponding preference degree coefficients is constructed as follows:
further, in S23, a combined weighted-TOPSIS-gray correlation analysis method is used to comprehensively evaluate the AGC frequency modulation performance of the power grid, and the calculation steps are as follows:
(1) determining a weighted decision matrix Z:
Z＝Y×W (31)
wherein Z = (Z) ij ) pq ；Y＝(y ij ) pq ；W＝(w 1 ,w 2 ,…,w q )；
(2) Calculating positive and negative ideal solutions of the weighted decision matrix:
in the formula, z j + ＝(z ij ) max ；z j - ＝(z ij ) min ；
(3) Calculating Euclidean distances between each object to be evaluated and the positive and negative ideal solutions:
in the formula, d i + The Euclidean distance between the ith object to be evaluated and the positive ideal solution; d is a radical of i - The Euclidean distance between the ith object to be evaluated and the negative ideal solution;
(4) calculating the gray correlation coefficient of each object to be evaluated and the positive and negative ideal solution:
wherein rho is a resolution coefficient; r is ij + A j-th evaluation index of the ith object to be evaluated and a gray correlation coefficient of a positive ideal solution are obtained; r is ij - A gray correlation coefficient of the jth evaluation index and the negative ideal solution of the ith object to be evaluated;
(5) calculating the gray correlation degree of each object to be evaluated and the positive and negative ideal solutions:
in the formula, r i + The gray correlation degree of the ith object to be evaluated and the positive ideal solution is obtained; r is a radical of hydrogen i - The gray correlation degree of the ith object to be evaluated and the negative ideal solution is obtained;
(6) respectively carrying out dimensionless processing on the Euclidean distance and the grey correlation degree:
in the formula, D i + Is d i + A dimensionless processed value; d i - Is d i - After dimensionless treatmentThe value of (d); r i + Is r i + Numerical values after dimensionless processing; r i - Is r i - A dimensionless processed value;
(7) calculating the comprehensive closeness of each object to be evaluated:
in the formula, Q i + And Q i - Reflecting the distance between the ith object to be evaluated and the ideal solution from the front surface and the back surface respectively; s. the i The comprehensive proximity of the ith object to be evaluated; alpha is alpha 2 And beta 2 Is a scale factor.
The invention has the beneficial effects that:
1. the difference of AGC frequency modulation instructions and the output characteristics of a frequency modulation power supply under different disturbance working conditions is fully considered, and an evaluation index system is respectively constructed for the step and continuous disturbance working conditions; each evaluation index provided is convenient to calculate, the discrimination of the frequency modulation performance is higher, and the advantages and the value of high-quality frequency modulation resources can be embodied better;
2. when an evaluation index system is constructed, evaluation indexes are designed from the perspective of tracking the AGC instruction output condition by a frequency modulation power supply, and frequency-related evaluation indexes are also considered, so that the comprehensive evaluation result can more comprehensively reflect the frequency modulation effect and the frequency state in the adjusting process;
3. the method is characterized in that subjective and objective combination weighting is carried out on various indexes based on expert weighting and an entropy weighting method, a grey correlation degree analysis method is organically combined with a top technique order system (TOPSIS) approaching an ideal solution, comprehensive evaluation on the AGC frequency modulation performance of the power grid is achieved from two dimensions of static distance and dynamic trend, the evaluation result is more scientific, and the application value and the prospect are huge.
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In order to more clearly illustrate the embodiments or technical solutions in the prior art of the present invention, the drawings used in the description of the embodiments or prior art will be briefly described below, and it is obvious for those skilled in the art that other drawings can be obtained based on these drawings without creative efforts.
FIG. 1 is an overall process flow diagram of the present invention;
FIG. 2 is a diagram of an energy storage system model of the present invention;
FIG. 3 is a regional power grid frequency modulation dynamic model diagram based on ARR signals;
FIG. 4 is a dynamic load disturbance curve of the present invention;
FIG. 5 is a graph of dynamic adjustment rate index values for 3 modes of the present invention;
FIG. 6 is a graph of the dynamic adjustment accuracy index values for 3 modes of the present invention;
FIG. 7 is a graph of dynamic response time index values for 3 modes of the present invention;
fig. 8 is a graph of dynamic frequency deviation index values in 3 modes of the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
As shown in fig. 1, a comprehensive evaluation method for the frequency modulation performance of the AGC of a power grid includes the following steps:
s1, constructing a comprehensive index system of AGC frequency modulation performance of a power grid;
s11, constructing an AGC frequency modulation performance comprehensive index system under step disturbance;
the AGC frequency modulation performance comprehensive index system under the step disturbance comprises three refinement indexes of regulation rate, regulation precision and response time related to output, and six refinement indexes of maximum frequency deviation, steady-state frequency deviation, frequency fluctuation rate, frequency recovery rate, frequency deviation degree and frequency recovery time related to frequency;
adjustment rate index K 1 Reflecting the output response of the frequency modulation power supply to set the rate of the frequency modulation command, wherein the value is the ratio of the actual regulation rate of the frequency modulation power supply to the standard regulation rate; the actual regulation rate formula of the frequency-modulated power supply is as follows:
in the formula, v represents the regulation rate (MW/min) of the frequency modulation power supply during AGC regulation; p is e Represents the output (MW) of the frequency modulated power supply at the end of the regulation; p is s Represents the output (MW) of the frequency modulated power supply at the beginning of the regulation; t is e Represents the climbing section ending time (min) during AGC adjustment; t is a unit of s Represents a hill climbing start time (min) when AGC adjustment is performed;
the calculation of the adjustment rate index is as follows:
in the formula, K 1 Representing an AGC adjusting rate index of the frequency modulation power supply; v. of N Indicating the standard regulation rate (MW/min).
Adjustment accuracy index K 2 The size of AGC adjustment deviation of the frequency modulation power supply is reflected; in the oscillation stage after the frequency modulation power supply climbs, integral calculation is carried out on the absolute value of the difference between the actual output of the frequency modulation power supply and the AGC command, then the integral value is divided by the integral time to obtain the average adjustment deviation amount of the time period, and the calculation expression is as follows:
in the formula, P bias Adjusting the deviation (MW) for the average adjustment; p is A For AGC command power (MW) at regulation; p (t) is the frequency modulation power output (MW) of the oscillation time period during adjustment; t is oc Is the oscillation period duration (min) at the time of adjustment;
adjustment accuracy index K 2 Is calculated as follows:
in the formula, K 2 Showing AGC adjusting precision index of the frequency modulation power supply; p N,bias The standard value representing the adjustment deviation is generally 1% (MW) of the rated power of the unit.
The response time is the time for the frequency modulation power supply to span out of a dead zone consistent with the adjustment direction after the AGC command is sent out; response time index K 3 The value is the ratio of the response time to the standard response time.
The response time indicator is calculated as follows:
in the formula, K 3 Representing an AGC response time index of the frequency modulation power supply; t represents a response time(s) when the frequency modulation power supply is adjusted; t is t N Represents a standard response time(s); the standard response time of the thermal power generating unit is 60s.
Maximum frequency deviation index D m The maximum fluctuation degree of the frequency is measured, and whether the frequency modulation effect meets the requirement of the electric energy quality or not can be intuitively reflected; maximum frequency deviation index D m Is calculated as follows:
in the formula D m Is the maximum frequency deviation index; d m Maximum value of absolute value of frequency deviation (Hz); d N,m Is an adjustment multiple (Hz) for increasing the degree of discrimination of the maximum frequency deviation index.
Steady state frequency deviation index D s The degree of frequency recovery to the baseline value at steady state regulation is measured. The steady state frequency deviation indicator is calculated as follows:
in the formula, ds is a steady-state frequency deviation index; d s As steady state frequency deviation value (Hz); d N,s Is an adjustment multiple (Hz) for increasing the degree of discrimination of the steady-state frequency deviation indicator.
Frequency fluctuation rate index V m The frequency drop or rise speed after the system is disturbed by the load is measured; the computational expression of the frequency fluctuation rate is:
in the formula, v m Representing the rate of frequency fluctuation (Hz/s); d is a radical of m Maximum value of absolute value of frequency deviation (Hz); t is t m Indicating the time at which the absolute value of the maximum frequency deviation occurs; t is t b Indicating the start of adjustment;
frequency fluctuation rate index V m Is calculated as follows:
in the formula, V m Is a frequency fluctuation rate index; v. of N,m To an adjustment multiple (Hz/s) for increasing the discrimination of the frequency fluctuation rate index.
Frequency recovery rate index V r The speed of the system frequency recovering to the reference value in the adjusting process is measured; the computational expression for the frequency recovery rate is:
in the formula, v r Represents the frequency recovery rate (Hz/s); d is a radical of m Maximum value of absolute value of frequency deviation (Hz); d is a radical of s Is the steady state frequency deviation value (Hz); t is t s Representing the time when the steady-state frequency deviation value occurs; t is t m Indicating the moment when the absolute value of the maximum frequency deviation occurs;
frequency recovery rate index V r Is calculated as follows:
in the formula, V r Is a frequency recovery rate indicator; v. of N,r To an adjustment factor (Hz/s) for increasing the frequency recovery rate index discrimination.
Frequency deviation index D d The average degree of frequency deviation from a reference value in the whole adjusting process is measured; the frequency total standard deviation expression of the whole adjusting process is as follows:
in the formula, σ 1 Represents the frequency total standard deviation (Hz) of the whole regulation process; n is s Numbering sampling points when the steady-state frequency is reached; f. of i Representing the system frequency (Hz) corresponding to the ith sampling point; f. of N Represents a reference frequency (Hz);
frequency deviation index D d Is calculated as follows:
in the formula D d Is a frequency deviation index; sigma 1N Is an adjustment multiple (Hz) for increasing the frequency deviation index discrimination.
Frequency recovery time index T r The time for adjusting the frequency until the frequency is stabilized after the system is disturbed by the load is measured; frequency recovery duration calculation tableThe shown formula is as follows:
t r ＝t s -t b (14)
in the formula, t r Represents a frequency recovery duration(s); t is t s Indicating the time at which the steady state frequency occurs; t is t b Indicating the adjustment start time;
frequency recovery time index T r Is calculated as follows:
in the formula, T r Is a frequency recovery time index; t is t N,r And a standard value(s) indicating the frequency recovery period.
S12, constructing an AGC frequency modulation performance comprehensive index system under continuous disturbance;
the AGC frequency modulation performance comprehensive index system under continuous disturbance comprises three refinement indexes of regulation rate, regulation precision and response time related to output and a frequency deviation index related to frequency;
adjusting the Rate index M 1 The degree of the power output of the frequency modulation power supply for tracking each AGC instruction is measured. Assuming that a new AGC command is issued at the time T and another AGC command is issued after a time length T, the following steps are provided:
in the formula, v 1 (t) the output regulation rate (MW/s) of the AGC instruction issued at the moment t is responded by the frequency modulation power supply; p (t) is the actual output Magnitude (MW) at the time t; v. of 2 (t) is the AGC command change rate (MW/s); p agc (t) an AGC command value (MW) issued at the time t; d is a radical of a (t) is the variation (MW) of two adjacent AGC commands;
evaluation of [ T, T + T]Adjusting the rate index M during AGC frequency modulation effect of a time interval 1 The definition is as follows:
in the formula, M 1 D is a judgment factor (MW) for adjusting the rate index; and considering that when the AGC instruction changes slightly (less than d), the output rate of the frequency modulation power supply can meet the requirement of quickly tracking the output change, and the adjustment rate index reaches the maximum value 1.
Adjustment accuracy index M 2 The deviation of the output response AGC instruction of the frequency modulation power supply is measured; assuming that T is the issuing time of the current AGC command and T is the interval time of two AGC commands, the following steps are provided:
m a (t)＝|P agc (t)-P(t+T)| (18)
in the formula, m a (t) is the final output response deviation (MW) of the frequency modulation power supply to the AGC command issued at the t moment; p agc (t) an AGC command value (MW) issued at the time t; p (t) is the actual output Magnitude (MW) at the time t;
evaluation of [ T, T + T]Adjusting precision index M during AGC frequency modulation effect of time interval 2 The definition is as follows:
in the formula, M 2 To adjust the accuracy index, m N,a (t) is the force response deviation threshold (MW).
The response time index measures the response delay time of the frequency modulation power supply to the AGC command; the invention combines the method for calculating the response accuracy and the time delay score of a frequency modulation power supply to an AGC instruction in the American PJM market, and provides a method for calculating a response time index under continuous load disturbance, which comprises the following steps:
the response time of the thermal power generating unit is generally required to be less than 60s, so that the sampling period of a single sample is set to be 100s; assuming that a new AGC command exists at the time t, taking the time as an initial time, taking 10s as a sampling interval time, and reading a sequence { P with the number of 100s of AGC command constituent elements being 11 agc }; similarly, 10s is taken as the sampling data interval time, the frequency modulation power supply 100s later is read respectively from the time t and then is sequentially taken back every 10s as the starting timeForce values, forming 11 different sequences { P } n (1. Ltoreq. N.ltoreq.11), wherein each sequence comprises 11 elements; calculating the { P in turn according to the sampling sequence agc And { P } and n the correlation coefficient of the two sequences is equal to or less than 1 and equal to or less than 11, and a new sequence { Cn } containing 11 elements is formed; the specific calculation expression is as follows:
in the formula, C n Is a sequence { P agc And { P } and n -correlation coefficient of; t is a unit of d A response delay time(s); delta t is sampling interval time(s), and 10s is taken in the invention; i is the sampling point serial number corresponding to the response time, and the calculation formula is defined as follows:
wherein p is the sequence { C n The sequence number of the sampling point corresponding to the maximum element in the sequence is obtained; q is the sequence { C n The first of which is larger than C N The sampling point sequence number corresponding to the element of (1); c q Is a sequence { C n The first of which is greater than C N An element of (1); c N Is a correlation coefficient reference value;
response time index M 3 The definition is as follows:
in the formula, M 3 In order to respond to the time index, m is the number of sampling points, and the value of the invention is 11.
Frequency deviation index F d The average degree of frequency deviation from a reference value in the AGC adjusting process is measured; supposing that a new AGC instruction appears at the time T and the issuing period of the instruction is T;
for the [ T, T + T ] period, the overall standard deviation of the frequency for the entire tuning process is expressed as:
in the formula, σ 2 Representing the frequency overall variance (Hz) over the time period; n is z The number of the last sampling point in the time interval; f. of i Representing the system frequency (Hz) corresponding to the ith sampling point; f. of N Indicating the reference frequency (Hz).
Evaluation of [ T, T + T]Frequency deviation index F during AGC frequency modulation effect of time interval d The definition is as follows:
in the formula, F d As an index of frequency deviation sigma 2N Is an adjustment multiple (Hz) for increasing the frequency deviation index discrimination.
S2, constructing a comprehensive evaluation method of the AGC frequency modulation performance of the power grid based on a combined weighting-TOPSIS-grey correlation degree model; the method specifically comprises the following steps:
s21, dimensionless processing;
supposing p objects to be evaluated and q evaluation indexes, thereby constructing an initial evaluation matrix of p multiplied by q; assuming that each evaluation index value in the matrix is Xij (i =1, 2.. Eta., p; j =1, 2.. Eta., q); because the dimensions of the index values in the matrix are not consistent, the original data is subjected to non-dimensionalization treatment; in order to better use the TOPSIS method in the follow-up process and enable the comprehensive evaluation result to be more accurate, the invention adopts a vector normalization method to carry out dimensionless treatment on data, and the treatment formula is as follows:
in the formula, x ij The original numerical value of the jth evaluation index of the ith object to be evaluated is obtained; y is ij Is x ij The values after dimensionless processing.
S22, determining index comprehensive weight based on a subjective and objective combination weighting method;
when multi-index comprehensive evaluation is carried out, each index needs to be weighted; in order to reflect the influence of each index on an evaluation system more objectively, the invention uses an entropy weight method in an objective weighting method to calculate the objective weight of each AGC frequency modulation performance index; the entropy weight method is to determine the weight of each index according to the variation degree of the evaluation index; generally, the higher the variation degree of a certain index is, the more information transmitted by the index is, the greater the influence on the comprehensive evaluation result is, and the greater the weight is given to the index; the formula of the index objective weighting calculation based on the entropy weight method is as follows:
(1) each index is standardized, and the calculation formula is as follows:
in the formula, c ij The index value is the index value after the j-th evaluation index of the ith object to be evaluated is normalized;
(2) calculating entropy values of indexes, wherein the calculation formula is as follows:
in the formula, e j Entropy value of j-th evaluation index;
(3) determining the objective weight of each index, and calculating the formula as follows:
in the formula, w k j The objective weight of the jth evaluation index;
in order to give consideration to the intuitive cognition of a decision maker on the importance ranking of each evaluation index of the AGC frequency modulation performance of the power grid and the objective rule of index data reflection, the invention combines the subjective weight and the objective weight and adopts a subjective and objective combination weighting method to obtain the comprehensive weight of each index; subjective weights of all evaluation indexes are obtained by adopting an expert weighting method; the calculation steps of the subjective and objective combination weighting algorithm are as follows:
(1) constructing an optimization decision model, wherein the comprehensive weight calculation formula is as follows:
in the formula, w j The comprehensive weight of the jth evaluation index; w is a z j The subjective weight of the jth evaluation index; alpha is alpha 1 And beta 1 Preference degree coefficients respectively representing subjective and objective weights.
(2) Introducing Euclidean distance function d (w) z j ，w k j ) The difference degree relation equation between the subjective and objective weights and the corresponding preference degree coefficients is constructed as follows:
in order to keep the difference degree between the subjective and objective weights and the corresponding preference degree coefficients consistent, the joint type (32) and the formula (33) are solved, and an ideal comprehensive weight result can be obtained.
S23, constructing a TOPSIS-grey correlation degree model, and determining a comprehensive evaluation result of the AGC frequency modulation performance of the power grid;
the top ranking method (TOPSIS) approaching to the ideal solution is an effective multi-index decision method, which has been widely used as a classical comprehensive evaluation method, but has the following disadvantages: (1) each evaluation index is subjected to non-difference weighting or has the defect of subjective weighting; (2) if the Euclidean distances of two evaluation objects are the same, the order of the two evaluation objects cannot be distinguished. Aiming at the problems, the invention carries out subjective and objective combined weighting on each index based on expert weighting and an entropy weight method, organically combines a gray correlation degree analysis method with a TOPSIS method, adopts the combined weighting-TOPSIS-gray correlation degree analysis method to comprehensively evaluate the AGC frequency modulation performance of the power grid, and comprises the following calculation steps:
(1) determining a weighting decision matrix Z:
Z＝Y×W (31)
wherein Z = (Z) ij ) pq ；Y＝(y ij ) pq ；W＝(w 1 ,w 2 ,…,w q )；
(2) Calculating positive and negative ideal solutions of the weighted decision matrix:
in the formula, z j + ＝(z ij ) max ；z j - ＝(z ij ) min ；
(3) Calculating Euclidean distances between each object to be evaluated and the positive and negative ideal solutions:
in the formula (d) i + The Euclidean distance between the ith object to be evaluated and the positive ideal solution; d i - The Euclidean distance between the ith object to be evaluated and the negative ideal solution;
(4) calculating the gray correlation coefficient of each object to be evaluated and the positive and negative ideal solutions:
in the formula, rho is a resolution coefficient, and the maximum information content can be kept in the association degree when the value is usually 0.5; r is ij + A j-th evaluation index of the ith object to be evaluated and a grey correlation coefficient of the positive ideal solution are obtained; r is ij - A gray correlation coefficient of the jth evaluation index and the negative ideal solution of the ith object to be evaluated;
(5) calculating the gray correlation degree of each object to be evaluated and the positive and negative ideal solutions:
in the formula, r i + The gray correlation degree of the ith object to be evaluated and the positive ideal solution is obtained; r is i - The gray correlation degree of the ith object to be evaluated and the negative ideal solution is obtained;
(6) respectively carrying out non-dimensionalization on the Euclidean distance and the grey correlation degree:
in the formula, D i + Is d i + Numerical values after dimensionless processing; d i - Is d i - A dimensionless processed value; r i + Is r i + Numerical values after dimensionless processing; r is i - Is r i - A dimensionless processed value;
(7) calculating the comprehensive proximity of each object to be evaluated:
in the formula, Q i + And Q i - Reflecting the distance between the ith object to be evaluated and the ideal solution from the front surface and the back surface respectively; s i The comprehensive proximity of the ith object to be evaluated; alpha (alpha) ("alpha") 2 And beta 2 The values of the invention are respectively 0.5 for the proportionality coefficient;
ranking the evaluation objects according to the obtained comprehensive proximity value; the larger the comprehensive proximity value is, the better the AGC frequency modulation performance is.
Specific examples are as follows:
when the stored energy is used for power grid AGC frequency modulation, because certain response delay exists when the AGC frequency modulation command is tracked for charging/discharging, a first-order inertia link is selected as a transfer function for description, and a specific expression is as follows:
in the formula, G B For the energy storage system transfer function, T B Is the time constant of the energy storage response.
An energy storage model facing the power grid AGC frequency modulation is shown in FIG. 2; in the figure, T B Is the time constant of the energy storage system; p B,ref An active power target instruction of the energy storage system is given; p is B And outputting the active power for the energy storage system actually.
Establishing a regional power grid frequency modulation dynamic model containing an energy storage system based on a regional regulation demand (ARR) signal distribution mode, as shown in figure 3; in the figure, Δ f is the system frequency deviation; delta P line Exchanging power for interconnected grid tie lines; k I Is the integral coefficient of the PI regulator; k is k Is the proportionality coefficient of the PI regulator; b is a secondary frequency modulation frequency deviation coefficient; p Gi A secondary frequency modulation output instruction of the ith traditional thermal power generating unit; p Bj A secondary frequency modulation output instruction of the jth energy storage system; p Gi1 The power is output for the primary frequency modulation of the ith traditional thermal power generating unit; p' Gi The active power is the actual output active power of the ith traditional thermal power generating unit; p' Bj The active power actually output by the jth energy storage system; p Ld Is system net load fluctuation; t is g Is the governor time constant; t is r Is the reheat time constant; t is t Is the generator time constant; r is a unit difference adjustment coefficient; k is r Is the reheat coefficient; k p Is the system gain; t is p Is the system time constant.
Model parameters:
according to the technical characteristics, the output characteristics, the frequency modulation characteristics and the like of the thermal power generating unit and the energy storage system, the following table 1 is set for the parameters of the regional power grid frequency modulation dynamic model:
TABLE 1 regional power grid frequency modulation dynamic model parameters
A simulation model is built by utilizing a Matlab/Simulink platform and a Matlab Function module, the installed capacity of the system is set to be 1000MW, and the selected reference power is 1000MW. The energy storage rated power is +/-30 MW, the energy storage rated capacity is 15MW & h, the standby capacity of the thermal power generating unit is 60MW, and the climbing rate is 3%/min of the rated power.
Comparison of frequency modulation performance under step disturbance condition
Selecting disturbance conditions as follows: step load disturbance of 0.022p.u. was added to the system at 10 s. The indexes and the related parameter settings in the comprehensive evaluation algorithm are as follows in table 2:
TABLE 2 frequency-modulation performance index parameters under step disturbance
The invention carries out simulation comparison on the frequency modulation of the regional power grid under 3 different modes, and the obtained index results are shown in the following tables 3-5; the mode 1 is AGC frequency modulation (no energy storage) of a thermal power generating unit; mode 2 is fire-storage combined AGC frequency modulation by adopting a difference compensation method; mode 3 is a fire-storage joint AGC frequency modulation using a static proportional distribution method (the coefficient ratio of the unit to the stored energy is 6.5.
TABLE 3 evaluation index values relating to output
TABLE 4 frequency-dependent evaluation index values
Table 3 shows evaluation index values related to output in 3 frequency modulation modes. It can be seen that the performance of the regulation rate and the response time when the energy storage unit is equipped to participate in the AGC frequency modulation of the power grid under the step load disturbance is obviously superior to that of the unit frequency modulation without energy storage, and the performance of the difference compensation method adopted for the combined frequency modulation of the power grid and the energy storage is superior to that of the static proportion distribution method.
Table 4 shows the evaluation index values of frequency dependence in 3 frequency modulation modes. It can be seen that the performance is optimal when the fire storage combined AGC frequency modulation is carried out by adopting a difference compensation method under the step load disturbance; the frequency fluctuation degree is obviously improved by the frequency modulation of the set equipped with the energy storage; the 3 frequency modulation modes can recover the frequency to a reference value, but the frequency recovery speed when the fire storage combination carries out AGC frequency modulation is obviously faster than that of the unit frequency modulation without energy storage, and the recovery time is shortest when a difference compensation method is adopted.
The condition of the performance of the frequency modulation obtained by the indexes accords with the practical application, the discrimination of each index is higher, and the effectiveness of the provided index system is verified.
The evaluation index values obtained above were subjected to dimensionless processing, and the calculation results are shown in table 5 below.
TABLE 5 nondimensionalized index values under step disturbance
Substituting the non-dimensionalized index data into an index weighting algorithm based on a subjective and objective combination weighting method to obtain a preference degree coefficient (alpha) 1 ，β 1 ) The values are (0.2939, 0.7061), and the results of the index weights obtained are shown in Table 6 below.
TABLE 6 weight results of various indexes under step disturbance
Constructing a weighting decision matrix, and solving a positive and negative ideal solution as follows:
thus, the euclidean distance and the gray degree of correlation with the positive and negative ideal solutions in the 3 modes can be obtained, and the respective results are dimensionless processed, and the calculation results are shown in table 7 below.
TABLE 7 Euclidean distance and Gray correlation for 3 modes under step disturbance
According to the results in table 7, the relative proximity and the comprehensive proximity of the grid AGC frequency modulation performance of the 3 frequency modulation modes under the step disturbance are calculated, and the results are shown in table 8 below.
TABLE 8 relative proximity under step disturbance and Total proximity results
The larger the comprehensive proximity is, the better the AGC frequency modulation performance of the power grid is. According to the results in table 8, the order of the frequency modulation performance of the 3 frequency modulation modes under the step disturbance is as follows: mode 2> mode 3> mode 1. The obtained condition of the frequency modulation performance accords with practical application, and the effectiveness of the comprehensive evaluation method for the AGC frequency modulation performance of the power grid is verified.
Frequency-modulation performance comparison under continuous disturbance working condition
Selecting a dynamic load disturbance mode as shown in figure 4; the method comprises various disturbance working conditions such as continuous low frequency, continuous high frequency and step.
The indexes and related parameter settings in the comprehensive evaluation algorithm are as follows in table 9:
TABLE 9 frequency modulation Performance index parameters under continuous disturbance
The method carries out simulation comparison on frequency modulation of a regional power grid under 3 different modes, wherein the mode 1 is AGC (automatic gain control) frequency modulation (no energy storage) of a thermal power generating unit; mode 2 is fire-storage combined AGC frequency modulation by adopting a difference compensation method; mode 3 is a fire-storage joint AGC frequency modulation using a static proportional distribution method (the coefficient ratio of the unit to the stored energy is 6.5. The obtained index results are shown in figures 5-8 (index results within one hour after 100s selection).
Figures 5-7 show the dynamic index values associated with the output in 3 frequency modulation modes. It can be seen that under the load disturbance working condition of slow change and low frequency, the frequency modulation index values of 3 modes are all approximate to the maximum index value, which shows that the frequency modulation indexes have better frequency modulation performance; for high-frequency and step load disturbance, index values of regulation rate and regulation precision in 3 modes are reduced and fluctuated to different degrees, wherein the index value of the unit frequency modulation without energy storage falls and fluctuates maximally, and the fluctuation amplitude of the index value is minimal when the fire storage combined AGC frequency modulation is performed by adopting a difference compensation method, so that the condition that the fire storage combined frequency modulation is performed by adopting the difference compensation method under the working condition of high-frequency continuous load disturbance with high change rate and high frequency has better frequency modulation performance is reflected.
Fig. 8 shows the dynamic frequency deviation index values associated with the frequencies in 3 frequency modulation modes. It can be seen that under the load disturbance working condition of slow change and low frequency, the frequency deviation index values of the 3 modes are all approximate to the index peak value, and the frequency deviation index values are reflected to have better frequency modulation performance; under the condition of high-speed change and large-amplitude high-frequency load disturbance, the index values of the 3 modes are reduced and fluctuated to different degrees, wherein the index values are most obvious in falling and fluctuation amplitude when only a unit (without stored energy) participates in frequency modulation, and the fluctuation amplitude of the index values is minimum when a difference compensation method is adopted to carry out fire-stored combined AGC frequency modulation. The method shows that under the condition of large-amplitude high-frequency load disturbance, the frequency fluctuation condition is obviously improved by the energy storage auxiliary unit participating in the AGC frequency modulation of the power grid, and the performance of the difference compensation method is superior to that of the static proportion distribution method.
The condition of the performance of the frequency modulation obtained by the indexes accords with the practical application, the discrimination of each index is higher, and the effectiveness of the provided index system is verified.
According to an index weighting algorithm based on a subjective and objective combination weighting method, various index values under 3 frequency modulation modes in a high-frequency load disturbance section (within 2500-3500 s) are selected, a 300 x 4-dimensional initial evaluation matrix is constructed for index weight calculation, preference degree coefficients (alpha 1, beta 1) are obtained as (0.2939, 0.7061), and the weight calculation results of the various obtained indexes are shown in the following table 10:
TABLE 10 results of various index weights under continuous disturbance
The mean values of the indexes in the 3 frequency modulation modes in the sampling hour are calculated and subjected to dimensionless processing, and the results are shown in the following table 11.
TABLE 11 mean dimensionless values of the indices
According to the results in table 10 and table 11, a weighting decision matrix is constructed, and the positive and negative ideal solutions are obtained as follows:
from this, the euclidean distance and the gray degree of correlation with the positive and negative ideal solutions in the 3 modes can be obtained, and each of them is subjected to the dimensionless processing, and the calculation results are shown in table 12 below.
TABLE 12 Euclidean distance and Gray correlation degree for 3 modes under continuous disturbance
According to the results in table 12, the relative proximity and the comprehensive proximity of the grid AGC frequency modulation performance of the 3 frequency modulation modes under continuous disturbance are calculated, and the results are shown in table 13 below.
TABLE 13 relative proximity under continuous perturbation and integrated proximity results
The larger the comprehensive proximity is, the better the AGC frequency modulation performance of the power grid is. According to the results in table 13, the order of the frequency modulation performance of 3 frequency modulation modes under continuous disturbance is as follows: mode 2> mode 3> mode 1.
Due to the high-frequency and large-fluctuation load disturbance, the comprehensive proximity of the 3 modes is obviously different, wherein the comprehensive proximity value of the mode 2 is the largest, the frequency modulation performance is the best, and the comprehensive proximity value of the mode 3 is slightly lower than that of the mode 2 but is obviously higher than that of the mode 1. The method shows that for continuous load disturbance under various working conditions, the overall performance of the fire-storage combined AGC frequency modulation is superior to that of the unit frequency modulation without energy storage.
The obtained condition of the frequency modulation performance accords with practical application, and the effectiveness of the comprehensive evaluation method for the AGC frequency modulation performance of the power grid is verified.
In summary, the invention provides a comprehensive evaluation method for the frequency modulation performance of the power grid AGC based on combined weighting-TOPSIS-grey correlation degree analysis, which is based on the purposes of researching the current situation and the deficiency of the comprehensive evaluation method for the frequency modulation performance of the power grid AGC, combining the existing evaluation method, encouraging more high-quality resources to be added into the frequency modulation auxiliary service market and the like based on the optimized AGC frequency modulation performance evaluation mechanism: corresponding AGC frequency modulation performance evaluation index systems are respectively constructed for step/continuous load disturbance working conditions, and a comprehensive evaluation method for the AGC frequency modulation performance of the power grid is provided based on a subjective and objective combination weighting-TOPSIS-grey correlation degree analysis method. A regional power grid dynamic frequency modulation model containing an energy storage system is constructed, and a simulation experiment is carried out on the comprehensive evaluation method of the AGC frequency modulation performance of the power grid under the condition of step/continuous load disturbance by utilizing a Matlab/Simulink platform. Simulation results show that the AGC frequency modulation performance evaluation index system constructed by the invention can better embody the superiority of the energy storage auxiliary unit in the aspects of regulating the frequency modulation performance such as speed, regulating precision, response time, frequency fluctuation inhibition and the like of AGC frequency modulation in a joint manner under the working condition of step/continuous load disturbance, has higher differentiation degree of the frequency modulation performance of different frequency modulation modes, and can better embody the superiority and value of high-quality frequency modulation resources. The comprehensive evaluation method for the frequency modulation performance evaluates the performance conditions of different frequency modulation modes from two dimensions of static distance and dynamic trend, the comprehensive evaluation result accords with practical application, and reference can be provided for a power grid AGC frequency modulation performance evaluation mechanism formulated by a frequency modulation service market.
In the description herein, references to the description of "one embodiment," "an example," "a specific example" or the like are intended to mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above do not necessarily refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.
The foregoing shows and describes the general principles, essential features, and advantages of the invention. It will be understood by those skilled in the art that the present invention is not limited to the embodiments described above, which are given by way of illustration of the principles of the present invention, but that various changes and modifications may be made without departing from the spirit and scope of the invention, and such changes and modifications are within the scope of the invention as claimed.
Claims (10)
1. A comprehensive evaluation method for AGC frequency modulation performance of a power grid is characterized by comprising the following steps:
s1, constructing an AGC frequency modulation performance comprehensive index system under step disturbance and an AGC frequency modulation performance comprehensive index system under continuous disturbance;
s2, constructing a comprehensive evaluation method of the AGC frequency modulation performance of the power grid based on a combined weighting-TOPSIS-grey correlation degree model; the method specifically comprises the following steps:
s21, dimensionless processing;
s22, determining index comprehensive weight based on a subjective and objective combination weighting method;
s23, constructing a TOPSIS-grey correlation degree model, and determining a comprehensive evaluation result of the AGC frequency modulation performance of the power grid;
in S1, an AGC frequency modulation performance comprehensive index system under step disturbance comprises three indexes of regulation rate, regulation precision and response time related to output, and six indexes of maximum frequency deviation, steady-state frequency deviation, frequency fluctuation rate, frequency recovery rate, frequency deviation and frequency recovery time related to frequency;
the AGC frequency modulation performance comprehensive index system under continuous disturbance comprises three indexes of regulation rate, regulation precision and response time related to output and a frequency deviation index related to frequency.
2. The comprehensive evaluation method for the AGC frequency modulation performance of the power grid according to claim 1, wherein the calculation expressions of three indexes related to output in an AGC frequency modulation performance comprehensive index system under step disturbance are respectively as follows:
1) Adjusting the rate index:
in the formula, v represents the regulation rate of the frequency modulation power supply during AGC regulation; p is e Indicating the output of the frequency-modulated power supply at the end of the adjustment; p is s Indicating the output of the frequency-modulated power supply at the beginning of the regulation; t is e Representing the climbing section ending time when AGC is adjusted; t is s Representing the starting time of a climbing section when AGC is adjusted; k 1 Representing an AGC adjusting rate index of the frequency modulation power supply; v. of N Indicating a standard rate of adjustment;
2) Adjusting precision indexes:
in the formula, P bias The deviation amount is averagely adjusted during adjustment; p is A The AGC command power is adjusted; p (t) is the output of the frequency modulation power supply in the oscillation time period during adjustment; t is a unit of oc Is the oscillation time interval duration in the adjustment; k is 2 Showing AGC adjusting precision index of the frequency modulation power supply; p is N,bias A standard value representing an amount of adjustment deviation;
3) Response time index:
in the formula, K 3 Representing an AGC response time index of the frequency modulation power supply; t represents the response time when the frequency modulation power supply is adjusted; t is t N Indicating the standard response time.
3. The comprehensive evaluation method for the AGC frequency modulation performance of the power grid according to claim 2, characterized in that under step disturbance, the calculation expressions of six indexes related to frequency in the AGC frequency modulation performance comprehensive index system are respectively as follows:
1) Maximum frequency deviation index:
in the formula D m Is the maximum frequency deviation index; d m Is the maximum value of the absolute value of the frequency deviation; d N,m Adjusting multiple for increasing the maximum frequency deviation index discrimination;
2) Steady state frequency deviation index:
in the formula, ds is a steady-state frequency deviation index; d s Is a steady state frequency deviation value; d N,s Adjusting multiple for increasing steady state frequency deviation index discrimination;
3) Frequency fluctuation rate index:
in the formula, v m Representing the rate of frequency fluctuation; d is a radical of m Is the maximum value of the absolute value of the frequency deviation; t is t m Indicating the moment when the absolute value of the maximum frequency deviation occurs; t is t b Indicating the start of adjustment; v m Is a frequency fluctuation rate index; v. of N,m Adjusting multiple for increasing frequency fluctuation rate index differentiation;
4) Frequency recovery rate index:
in the formula, v r Represents a frequency recovery rate; d is a radical of m Is the maximum value of the absolute value of the frequency deviation; d s Is the steady state frequency offset value); t is t s Representing the time when the steady-state frequency deviation value occurs; t is t m Indicating the moment when the absolute value of the maximum frequency deviation occurs; v r Is a frequency recovery rate indicator; v. of N,r Is an adjustment multiple for increasing the frequency recovery rate index discrimination;
5) Frequency deviation index:
in the formula, σ 1 Represents the total standard deviation of the frequency of the whole adjusting process; n is a radical of an alkyl radical s Numbering sampling points when the steady-state frequency is reached; f. of i Representing the system frequency corresponding to the ith sampling point; f. of N Represents a reference frequency; d d Is a frequency deviation index; sigma 1N Adjusting multiple for increasing frequency deviation index differentiation;
6) Frequency recovery time index:
t r ＝t s -t b (14)
in the formula, t r Represents a frequency recovery duration(s); t is t s Represents the time at which the steady state frequency occurs; t is t b Indicating the adjustment start time; t is a unit of r Is a frequency recovery time index; t is t N,r A standard value indicating the frequency recovery period.
4. The comprehensive evaluation method for the AGC frequency modulation performance of the power grid according to claim 1, characterized in that under continuous disturbance, three indexes related to output in an AGC frequency modulation performance comprehensive index system are respectively calculated as follows:
1) Adjusting the rate index:
in the formula, v 1 (t) the output regulation rate of the frequency modulation power supply responding to the AGC instruction issued at the t moment; p (t) is the actual output at the moment t; v. of 2 (t) is the AGC command rate of change (; P) agc (t) an AGC command value issued at the time t; d is a radical of a (t) is the variation of two adjacent AGC commands; m 1 D is a judgment factor for adjusting the rate index;
2) Adjusting precision indexes:
m a (t)＝|P agc (t)-P(t+T)| (18)
in the formula, m a (t) the final output response deviation of the frequency modulation power supply to AGC commands issued at t moment; p agc (t) an AGC command value issued at the moment t; p (t) is the actual output at the moment t; m 2 To adjust the accuracy index, m N,a (t) is the output response deviation threshold;
3) Response time index:
in the formula, C n Is a sequence { P agc And { P } and n -correlation coefficient of; t is d Delay in response toA time(s); delta t is sampling interval time(s), and 10s is taken in the invention; i is the sampling point serial number corresponding to the response moment; p is the sequence { C n The sequence number of the sampling point corresponding to the maximum element in the sequence is obtained; q is the sequence { C n The first of which is larger than C N The sampling point sequence number corresponding to the element(s); c q Is a sequence { C n The first of which is greater than C N An element of (1); c N Is a correlation coefficient reference value; m is a group of 3 M is the number of sampling points as a response time index.
5. The comprehensive evaluation method for the AGC frequency modulation performance of the power grid according to claim 4, wherein in a comprehensive index system of the AGC frequency modulation performance under continuous disturbance, a calculation expression of a frequency deviation index related to frequency is as follows:
in the formula, σ 2 Representing the frequency overall variance (Hz) over the time period; n is z The number of the last sampling point in the time period is the number; f. of i Representing the system frequency (Hz) corresponding to the ith sampling point; f. of N Represents a reference frequency; f d As an index of frequency deviation sigma 2N Is an adjustment multiple for increasing the frequency deviation index discrimination.
6. The comprehensive evaluation method for the AGC frequency modulation performance of the power grid according to claim 1, wherein the formula for carrying out non-dimensionalization on the data in S21 is as follows:
in the formula, x ij Is the ith oneThe original value of the j-th evaluation index of the evaluation object; yij is x ij The values after dimensionless processing.
7. The comprehensive evaluation method for the AGC frequency modulation performance of the power grid according to claim 1, wherein the entropy weight method in the objective weighting method in S22 is used for calculating the objective weight of each AGC frequency modulation performance index, and the calculation formula is as follows:
(1) each index is standardized, and the calculation formula is as follows:
in the formula, c ij The index value is the index value after the j item evaluation index of the ith object to be evaluated is standardized;
(2) calculating entropy values of indexes, wherein the calculation formula is as follows:
in the formula, e j Entropy value of the j-th evaluation index;
(3) determining the objective weight of each index, and calculating the formula as follows:
in the formula, w k j Is the objective weight of the j-th evaluation index.
8. The comprehensive evaluation method for AGC frequency modulation performance of a power grid according to claim 7, wherein in S22, the calculation steps of the subjective and objective combination empowerment algorithm are as follows:
(1) constructing an optimization decision model, wherein the comprehensive weight calculation formula is as follows:
in the formula, w j The comprehensive weight of the jth evaluation index; w is a z j The subjective weight of the jth evaluation index; alpha is alpha 1 And beta 1 Preference degree coefficients respectively representing subjective and objective weights;
(2) introducing Euclidean distance function d (w) z j ，w k j ) The difference degree relation equation between the subjective and objective weights and the corresponding preference degree coefficients is constructed as follows:
9. the comprehensive evaluation method for the AGC frequency modulation performance of the power grid according to claim 8, wherein in the step S23, a combined weighted-TOPSIS-grey correlation degree analysis method is adopted to comprehensively evaluate the AGC frequency modulation performance of the power grid, and the calculation steps are as follows:
(1) determining a weighted decision matrix Z:
Z＝Y×W (31)
wherein Z = (Z) ij ) pq ；Y＝(y ij ) pq ；W＝(w 1 ,w 2 ,…,w q )；
(2) Calculating positive and negative ideal solutions of the weighted decision matrix:
in the formula, z j + ＝(z ij ) max ；z j － ＝(z ij ) min ；
(3) Calculating Euclidean distances between each object to be evaluated and the positive and negative ideal solutions:
in the formula, d i + The Euclidean distance between the ith object to be evaluated and the positive ideal solution; d is a radical of i － The Euclidean distance between the ith object to be evaluated and the negative ideal solution;
(4) calculating the gray correlation coefficient of each object to be evaluated and the positive and negative ideal solutions:
wherein rho is a resolution coefficient; r is ij + A j-th evaluation index of the ith object to be evaluated and a grey correlation coefficient of the positive ideal solution are obtained; r is ij － A gray correlation coefficient of the jth evaluation index and the negative ideal solution of the ith object to be evaluated;
(5) calculating the gray correlation degree of each object to be evaluated and the positive and negative ideal solutions:
in the formula, r i + The gray correlation degree of the ith object to be evaluated and the positive ideal solution is obtained; r is a radical of hydrogen i － The gray correlation degree of the ith object to be evaluated and the negative ideal solution is obtained;
(6) respectively carrying out non-dimensionalization on the Euclidean distance and the grey correlation degree:
in the formula, D i + Is d i + A dimensionless processed value; d i － Is d i － A dimensionless processed value; r is i + Is r of i + Dimensionless processed numbersA value; r is i － Is r i － A dimensionless processed value;
(7) calculating the comprehensive proximity of each object to be evaluated:
in the formula, Q i + And Q i － Reflecting the distance between the ith object to be evaluated and the ideal solution from the front surface and the back surface respectively; s i The comprehensive proximity of the ith object to be evaluated; alpha is alpha 2 And beta 2 Is a scale factor.
10. The method for comprehensively evaluating AGC frequency modulation performance of a power grid according to claim 9, wherein α in the formula (37) 2 And beta 2 Respectively taking the value of 0.5.
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN116187830A (en) * | 2023-01-06 | 2023-05-30 | 北京科技大学 | Comprehensive evaluation method for strip steel cold continuous rolling automation rate based on entropy weight-ideal solution |
| CN116187830B (en) * | 2023-01-06 | 2024-04-16 | 北京科技大学 | Comprehensive evaluation method for strip steel cold continuous rolling automation rate based on entropy weight-ideal solution |
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