CN105160166B - A kind of photovoltaic array state judging method - Google Patents
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Abstract
The present invention relates to a kind of photovoltaic array state judging method, collection influences the characteristic parameter of each photovoltaic array state；Time series node, photovoltaic array monitoring point are introduced, parametric model is established from horizontal, two dimensions in longitudinal direction；Construct the photovoltaic array running status assessment models based on positive Negative ideal point evaluation scheme；Using gaussian curve approximation method, the time function relation of condition evaluation results collection and each parameter in length and breadth is established, in conjunction with array I V curves and irradiation level temperature curve, from two angle accurate evaluation photovoltaic array present states in length and breadth, abnormal cause is analyzed, proposes O＆M measure.By carrying out state estimation according to many characteristic parameters, it is possible to increase the accuracy of state estimation, be advantageous to the real-time O＆M of photovoltaic array.Also, good basis also is established to improve the generating efficiency of photovoltaic array colony and seeking more excellent MPPT algorithm, there is stronger application value.
Description
Technical Field
The invention relates to a photovoltaic array state judgment method, and belongs to the technical field of safe operation of photovoltaic arrays.
Background
With the increasingly wide application of photovoltaic power generation technology, a large number of photovoltaic systems are put into operation, more photovoltaic system monitoring systems are researched domestically and abroad, and fewer operations and maintenance researches on photovoltaic power stations are conducted. The photovoltaic array is an integral module formed by connecting multiple photovoltaic modules in series or in series and parallel in order to achieve certain direct current electric energy output, the photovoltaic array is used as an important component of a photovoltaic power generation system, and the quality of the modules and the state of the photovoltaic array directly influence the power generation efficiency and the service life of the whole photovoltaic power generation system. Therefore, it is very important to monitor and evaluate the state of the photovoltaic array in real time and effectively in an unattended solar photovoltaic power station for a long time.
With the popularization and application of large-scale photovoltaic technologies, how to perform online evaluation on the state of a photovoltaic array in a photovoltaic system and find the reason of the failure of the photovoltaic array in time is very meaningful work. However, at present, monitoring of photovoltaic power generation systems at home and abroad only focuses on overall research, that is, only quantitative indexes such as output power, current and voltage of the whole photovoltaic power station are focused, and influences of external factors on the photovoltaic power station are often focused. In actual work, ambient temperature changes, illumination condition changes, factors such as irregular shadow shelters from make each photovoltaic module output characteristic difference appear in the photovoltaic array, each subassembly is in different operating condition promptly, lead to whole photovoltaic array output characteristic various, complicated, operating condition also can correspondingly change, ignore many environmental variables, subassembly self ageing and damage, external factors such as the combination rule and the installation quality of photovoltaic array, the positive clean degree of subassembly can cause the deviation to photovoltaic array state aassessment appearance.
Disclosure of Invention
The invention aims to provide a photovoltaic array state judgment method, which is used for solving the problem of inaccurate evaluation caused by no important attention to external factors because only quantitative indexes such as output power, current, voltage and the like of a whole photovoltaic power station are concerned when a photovoltaic array is evaluated in the prior art.
In order to achieve the above object, the present invention provides a method for judging a state of a photovoltaic array, comprising the steps of:
(1) Collecting characteristic parameters influencing the state of each photovoltaic array;
(2) Introducing time sequence nodes and photovoltaic array monitoring points, establishing a parameter model from two dimensions of transverse dimension and longitudinal dimension, and expressing the parameter model by using a characteristic parameter matrix as follows:
wherein: r ij ＝[R ij1 、R ij2 …R ijk ]；R m×n Representing m multiplied by n schemes to be evaluated for a longitudinal and transverse dimension characteristic parameter matrix; m: the number of the selected time sequence nodes; n: the number of the selected photovoltaic array monitoring points is determined; i: an ith time series node; j: the jth photovoltaic array monitoring point; r ij : a characteristic parameter set of the monitoring point j at the time node i represents a scheme to be evaluated; r is ijk : the kth characteristic parameter of the jth photovoltaic array at the i time nodes; k: the number of the characteristic parameters;
(3) Constructing a photovoltaic array running state evaluation model based on a positive ideal point evaluation scheme and a negative ideal point evaluation scheme;
(4) And establishing a time function relation between the state evaluation result and each longitudinal and transverse parameter by adopting a Gaussian curve fitting method, and evaluating the current state of the photovoltaic array from two angles of longitudinal and transverse directions by combining the array I-V curve and the irradiance-temperature curve.
The characteristic parameters comprise: irradiance, ambient temperature, component backplane temperature, component mismatch rate, shadow rate, dust deposition rate, aging rate, failure rate.
The step (3) is specifically as follows:
1) Constructing a positive ideal point state evaluation matrix and a negative ideal point state evaluation matrix;
2) Calculating the contribution value, and constructing a positive difference matrix and a negative difference matrix according to the contribution value;
3) Calculating a projection coefficient, and constructing a positive difference projection matrix and a negative difference projection matrix according to the projection coefficient;
4) And calculating the optimal distance of each scheme to be evaluated, and then evaluating the running state of the photovoltaic array in each scheme to be evaluated.
The step 1) is specifically as follows:
firstly, a state matrix X to be evaluated of different photovoltaic arrays at a certain moment is selected n×k The method comprises the following steps:
wherein n represents the number of the photovoltaic arrays, and k represents the number of the characteristic parameters;
selecting a certain photovoltaic array and state matrix Y to be evaluated at different moments m×k The method comprises the following steps:
wherein m is the number of time points of data acquisition on a time axis, and k represents the number of characteristic parameters;
then, for matrix X n×k Constructing a positive and negative ideal point state evaluation matrix X + 、X - : said X is + In, the first row data is AND X n×k Corresponding positive ideal evaluation scheme, and the rest is the matrix X n×k (ii) a Said X - In, the first row data is AND X n×k Corresponding negative ideal evaluation scheme, and the rest is the matrix X n×k ；
For matrix Y n×k Constructing a positive and negative ideal point state evaluation matrix Y + 、Y - : said Y + In, the first row data is and Y m×k Corresponding positive ideal evaluation scheme, and the rest is the matrix Y m×k (ii) a Said Y - In, the first row data is and Y m×k Corresponding negative ideal evaluation scheme, and the rest is the matrix Y m×k ；
The positive ideal evaluation scheme is an evaluation scheme in which all the characteristic parameters simultaneously take the best values, and the negative ideal evaluation scheme is an evaluation scheme in which all the characteristic parameters simultaneously take the worst values.
The step 2) is specifically as follows:
a) When the state evaluation is carried out on different photovoltaic arrays at the same time:
first, the contribution values w of k feature parameters are calculated j The calculation formula is as follows:
i 1 ≠i 2 and i is 1 ,i 2 ＝2,…,n+1，
Wherein i 1 ，i 2 Representing the different scenarios to be evaluated,
then, a positive difference matrix E is calculated + ＝X + W, and a negative difference matrix E - ＝X - W, where the disparity vector of the normalized feature parameters is w = (w) 1 ,w 2 ,…,w k ) And is made ofThe positive and negative difference matrices are represented as follows:
b) When evaluating the state of the same photovoltaic array at different times:
first, the contribution values w of k feature parameters are calculated o The calculation formula is as follows:
l 1 ≠l 2 and l 1 ,l 2 ＝2,…,m+1，
Wherein l 1 ，l 2 Indicating the different scenarios to be evaluated and,
then, a positive difference matrix E is calculated + ＝Y + W, and a negative difference matrix E - ＝Y - W, where the disparity vector of the normalized feature parameters is w = (w) 1 ,w 2 ,…,w k ) And is andthe positive and negative difference matrices are represented as follows:
the step 3) is specifically as follows:
a) When the state evaluation is carried out on different photovoltaic arrays at the same moment:
firstly, the forward projection coefficient of the t-th characteristic parameter of the s-th scheme to be evaluated projected to the t-th characteristic parameter of the positive ideal evaluation scheme and the negative projection coefficient of the t-th characteristic parameter of the s-th scheme to be evaluated projected to the t-th characteristic parameter of the negative ideal evaluation scheme are respectively as follows:
wherein the content of the first and second substances, the value of the t characteristic parameter of the positive ideal evaluation scheme is indicated, wherein t =1,2, \8230;, k;the method is characterized by comprising the following steps of (1) referring to the tth characteristic parameter value of the tth scheme to be evaluated, wherein s =2,3, \ 8230;, n, n +1;
the value of the t characteristic parameter of the negative ideal assessment scheme is indicated, wherein t =1,2, \8230;, k;the method is characterized by comprising the following steps of (1) referring to the tth characteristic parameter value of the tth scheme to be evaluated, wherein s =2,3, \ 8230;, n, n +1;
then, a positive and negative difference projection matrix P is calculated + 、P - The calculation formulas are respectively as follows:
b) When the state of the same photovoltaic array at different times is evaluated:
firstly, the forward projection coefficient of the t-th characteristic parameter of the s-th scheme to be evaluated projected to the t-th characteristic parameter of the positive ideal evaluation scheme and the negative projection coefficient of the t-th characteristic parameter of the s-th scheme to be evaluated projected to the t-th characteristic parameter of the negative ideal evaluation scheme are respectively as follows:
wherein the content of the first and second substances, the method refers to the value of the t characteristic parameter of an ideal evaluation scheme, wherein t =1,2, \8230;, k;the method is characterized by comprising the following steps of (1) referring to the tth characteristic parameter value of the tth scheme to be evaluated, wherein s =2,3, \ 8230;, m, m +1;
the t characteristic parameter value of a negative ideal evaluation scheme is indicated, wherein t =1,2, \8230;, k;the method is characterized by comprising the following steps of (1) referring to the tth characteristic parameter value of the tth scheme to be evaluated, wherein s =2,3, \ 8230;, m, m +1;
then, a positive and negative difference projection matrix Q is calculated + 、Q - The calculation formulas are respectively as follows:
the step 4) is specifically as follows:
a) When the state evaluation is carried out on different photovoltaic arrays at the same time:
firstly, calculating Euclidean distances of each scheme to be evaluated relative to positive and negative ideal evaluation schemes as follows:
then, an optimum distance D is calculated s Wherein s is a scheme to be evaluated, and the calculation formula is as follows:
finally, according to the optimal distance D s Performing state evaluation on different photovoltaic arrays at the same time;
b) When the state of the same photovoltaic array at different times is evaluated:
firstly, calculating Euclidean distances of each scheme to be evaluated relative to positive and negative ideal evaluation schemes as follows:
then, an optimum distance is calculatedD s Wherein s is a scheme to be evaluated, and the calculation formula is as follows:
finally, according to the optimal distance D s And carrying out state evaluation on the same photovoltaic array at different moments.
In the step (4), the time function relationship includes an irradiance-state evaluation value curve, a component backplane temperature-state evaluation value curve, a component mismatch rate-state evaluation value curve, and a dust deposition rate-state evaluation value curve.
In the step (4), the evaluating the current state of the photovoltaic array from the longitudinal and transverse angles specifically includes: in the longitudinal direction: when the photovoltaic array is under uniform illumination, if the state evaluation value is lower than a set value, the I-V curves of all the groups of strings of the photovoltaic array meet the same functional relation, and the power curve under the time sequence is a continuously reduced curve, the dust accumulation of the photovoltaic array is judged to be increased; at the transverse angle: when the optimal distance between the photovoltaic arrays A and B is 0.832 and 0.576 respectively, and the I-V curve and irradiance curve of the photovoltaic arrays A and B are the same in the same time period, if the component backplane temperature of B is higher than that of A, and if the on-stream time of A is A t On-stream time B greater than B t If so, the local hot spot phenomenon appears in B; if A is t <B t Then B has a component aging condition.
The method for judging the state of the photovoltaic array comprises the steps of collecting characteristic parameters influencing the state of the photovoltaic array, carrying out a series of matrix processing on the characteristic parameters, calculating comprehensive evaluation coefficients of all evaluation schemes according to the characteristic parameters, and evaluating the state according to conditions met by the evaluation coefficients, wherein the method comprises the following steps of: factors such as environment temperature change, illumination condition change, irregular shadow shielding and the like are also brought into conditions for evaluating the state of the photovoltaic array, and the state evaluation is carried out according to characteristic parameters in multiple aspects, so that the accuracy of the state evaluation can be improved, and the real-time operation and maintenance of the photovoltaic array are facilitated. In addition, a good foundation is laid for improving the power generation efficiency of the photovoltaic array group and seeking a better MPPT algorithm, and the method has a strong application value.
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Fig. 1 is a flow chart of a method for determining a state of a photovoltaic array.
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings.
As shown in fig. 1, the method for judging the state of the photovoltaic array according to the present invention first deeply analyzes the working state and the load state of the photovoltaic array and the characteristic parameters affecting the state of the photovoltaic array, then establishes a parametric model based on the vertical and horizontal dimensions, and then uses an analogy method to make the photovoltaic array equivalent to a photovoltaic module, and constructs a photovoltaic array group analogy evaluation model, thereby implementing the state evaluation of the photovoltaic array under real-time monitoring. The specific analysis is as follows:
firstly, when an object is comprehensively evaluated, all influencing factors are looked at, so that characteristic parameters influencing the state of the photovoltaic array are analyzed by combining actual operation conditions of various photovoltaic power stations. In the past, state parameters are more used as data bases, and the state parameters refer to attributes of parameters at a certain moment, namely transient values, and cannot reflect the dynamic characteristics of the parameters, namely the running states of equipment or a system cannot be accurately judged; the process parameter representation shows a continuous physical fluctuation process along with the change of time, reflects the dynamics and continuity of parameters, contains the trend information of the parameters, and the parameter representation form is generally a fluctuation curve, namely functional data. For example, the current and the voltage are the most direct main parameters reflecting the operation state of the photovoltaic array, and the process of continuously recording the parameter change directly reflects the real state of the photovoltaic array. It is known that the use of process parameters to detect or evaluate the operational state of a device or system is much more fully reliable than state parameters. For the state evaluation of the photovoltaic array, the influence factors are more, and the evaluation comprises array configuration mode, environmental factors, component self factors, shadow, dust and the like from the transverse dimension, continuous changes of solar irradiance, environmental temperature, battery backboard temperature, wind speed and the like from the longitudinal dimension, the service time of the photovoltaic cells and the like. These factors act together to affect the current-power output characteristic curve and the current-voltage output characteristic curve of the photovoltaic array. When the photovoltaic array fails or has other state changes, main parameters of the photovoltaic array also change, namely, the state characteristics of the photovoltaic array can be evaluated according to the data of the changes. The coverage area of the photovoltaic arrays in one photovoltaic field is large, and in order to simplify the state evaluation work of the photovoltaic arrays, the photovoltaic arrays of the whole photovoltaic power station are subjected to group evaluation by adopting an analogy evaluation method. The method is characterized in that a photovoltaic array is analogized to a photovoltaic module, a photovoltaic array with typical characteristics is selected from a photovoltaic array group to be used as a sample, and group analog state evaluation is carried out through organic combination of longitudinal and transverse parameters.
In the specific implementation, eight characteristic parameters for representing the state of the photovoltaic array, namely irradiance, ambient temperature, assembly backboard temperature, assembly mismatch rate, shadow rate (including cloud shielding), dust deposition rate, aging rate (namely power attenuation rate) and fault rate, are selected, and P = { P = 1 ,P 2 ,P 3 ,P 4 ,P 5 ,P 6 ,P 7 ,P 8 The characteristic parameter system can comprehensively provide accurate and reliable results for photovoltaic array population state evaluation.
Wherein, the values of irradiance, ambient temperature and component backboard temperature can be continuously collected by collection equipment such as an environmental monitor, the sampling time period is evaluated by combining the geographic environment of the photovoltaic power station, the state and the physical significance thereof, if a certain large-scale ground photovoltaic power station in Xinjiang is selected as an example, the longitude and latitude are known as east longitude 79 degrees and north latitude 36 degrees, and the value ranges of the irradiance, the ambient temperature and the component backboard temperature are respectively [600, 900], [32,38], [46,52] by combining the historical data of the power station; for the mismatch rate of the components, namely the imbalance rate among the components, the variance value of the current can be approximately expressed, and the value range is [0,1]; shadow rate, dust deposition rate, aging rate and failure rate can not be directly monitored, values can be obtained by combining actual engineering historical experience and expert experience, wherein the value range of the shadow rate is [0,1], the component is unavailable considering that the dust deposition rate, the aging rate and the failure rate reach a certain degree, and the value range of the three characteristic parameters is set to be [0,0.8].
And establishing a parametric model from the transverse dimension and the longitudinal dimension, and expressing the parametric model by using a characteristic parameter matrix. The transverse angle can be used for simulating the states of different photovoltaic arrays with different characteristic parameters at the same moment, and the influence degree of a certain characteristic parameter on the state of the photovoltaic array can be evaluated; the longitudinal angle can be similar to the state change of the same photovoltaic array along the time axis, and the real-time monitoring and evaluation of the state of the photovoltaic array are realized. Introducing time sequence nodes and photovoltaic array monitoring points, and constructing a characteristic parameter matrix as follows:
wherein:
R ij ＝[R ij1 、R ij2 …R ijk ]the parameters in the above matrix are described as follows:
r: a longitudinal and transverse dimension characteristic parameter matrix representing m multiplied by n schemes to be evaluated;
m: the number of the selected time sequence nodes;
n: the number of the selected photovoltaic array monitoring points is determined;
i: an ith time series node;
j: the jth photovoltaic array monitoring point;
R ij : a characteristic parameter set of the monitoring point j at the time node i represents a scheme to be evaluated;
R ijk : a kth characteristic parameter of the jth photovoltaic array at i time nodes;
k: the number of characteristic parameters.
And selecting a certain moment, wherein the state matrixes to be evaluated of different photovoltaic arrays are as follows:
wherein n represents the number of the photovoltaic arrays participating in comparison, and k represents the number of the characteristic parameters.
And selecting a certain photovoltaic array, wherein the state matrix to be evaluated, which runs along the time axis, of the photovoltaic array is as follows:
wherein m is the number of time points of data acquisition on the time axis, and k represents the number of characteristic parameters.
Then, positive and negative ideal evaluation schemes are added according to the matrixes X and Y respectively, and meanwhile, whether the characteristic parameters belong to benefit type indexes, cost type indexes or moderate type indexes is considered, only irradiance belongs to the benefit type indexes, and other indexes belong to the cost type indexes. The positive ideal evaluation scheme refers to an evaluation scheme in which all the characteristic parameters simultaneously take the best values, and the negative ideal evaluation scheme refers to an evaluation scheme in which all the characteristic parameters simultaneously take the worst values. For matrix X, the positive ideal eigenvector at time point 11: p = {900,32,46, 0}, the negative ideal eigenvector is: p = {600,38,52,1, 0.8}.
Then, converting the matrixes X and Y into augmented matrixes, taking the matrix X as an example (subsequently, taking X as an example to realize the evaluation and comparison of the running states of different photovoltaic arrays at the same moment; if Y is selected, carrying out the evaluation and analysis of the states of one photovoltaic array at different moments, wherein the evaluation process is the same as that of X), and carrying out normalization processing and marking as X' n×k Then, a positive ideal point state evaluation matrix is constructed and marked as X + ＝(X ij + ) (n+1)×k Constructing a negative ideal point state evaluation matrix, and marking as X - ＝(X ij - ) (n+1)×k Wherein i =1,2, \8230, n, n +1; j =1,2, \8230;, k. Is just goingIn the ideal dot matrix, the first row of data X 1j + ＝(X 11 + ，X 12 + ，…，X 1k + ) To be willing to evaluate the solution, it is set as the reference solution, while the other row of data X is 2j + 、X 3j + 、…、X (n+1)j + All participating in the evaluation of the status of the scheme X to be evaluated n×k The data of (1). Similarly, for matrix Y n×k Constructing a positive and negative ideal point state evaluation matrix Y + 、Y - ：Y + In the first row, the data is Y m×k Corresponding positive ideal evaluation scheme, and the rest is matrix Y m×k The data of (1); y is - In the first row, the data is Y m×k Corresponding negative ideal evaluation scheme, and the rest is matrix Y m×k The data of (1).
In general, the larger the evaluation difference of each scheme under a certain characteristic parameter, the larger the contribution of the characteristic parameter to the evaluation result, and vice versa.
Based on the above, when the state evaluation is carried out on different photovoltaic arrays at the same time,
first, the contribution values of k feature parameters are calculated as w j Expressed, the calculation formula is:
i 1 ≠i 2 and i is 1 ,i 2 ＝2,…,n+1
Wherein i 1 ，i 2 Representing different scenarios to be evaluated. For evaluating the difference valueIs defined as follows:
the disparity vector of the normalized feature parameter is w = (w) 1 ,w 2 ,…,w k ) And is andthen, a positive difference matrix E is obtained + ＝X + W, similarly, can obtain a negative difference matrix E - ＝X - ·w。
The positive and negative difference matrices are represented as follows:
then, in normalized ideal matrix X + In the middle, letWherein, the first and the second end of the pipe are connected with each other,the value of the t characteristic parameter of the positive ideal evaluation scheme is indicated, wherein t =1,2, \8230;, k;the method is characterized by comprising the following steps of (1) referring to the tth characteristic parameter value of the tth scheme to be evaluated, wherein s =2,3, \ 8230;, n, n +1; order to The t characteristic parameter value of a negative ideal evaluation scheme is indicated, wherein t =1,2, \8230;, k;is the t-th characteristic parameter value of the s-th scheme to be evaluated, wherein s =2,3, \ 8230;, n, n +1.
Then, defining t characteristic parameter of s scheme to be evaluated and projecting it to positive ideal evaluating partyThe positive projection coefficient of the tth characteristic parameter of the scheme and the negative projection coefficient of the tth characteristic parameter of the obtained s-th scheme to be evaluated projected to the tth characteristic parameter of the negative ideal evaluation schemeRespectively as follows:
calculating a positive and negative difference projection matrix P + 、P - The calculation formulas are respectively as follows:
then, calculating Euclidean distances of each scheme to be evaluated relative to the positive and negative reference schemes as follows:
according to the formula, the compound is shown in the specification,the smaller, the closer the solution s to be evaluated is to the positive reference solution,the smaller the solution s to be evaluated is to the negative reference solution. For the case of the scenario s to be evaluated,the smaller the size, the better,the larger the better, the best solution is closest to the positive reference solution, while the farthest is from the negative reference solution, define D s For the best distance between the solution s to be evaluated and the positive reference sequence, the best distance between the solution s to be evaluated and the negative reference sequence is 1-D s 。
Will optimize the distance degree D s As the state evaluation value of the photovoltaic array, the method can realize the order of the advantages and disadvantages of each scheme, only one characteristic parameter of each scheme is set to be different, and the other characteristic parameter values are kept consistent, so that the optimal distance degree can judge the influence degree of the characteristic parameter on the state of the photovoltaic array, and similarly, the interaction degree of a plurality of characteristic parameters on the state of the photovoltaic array can be evaluated.
Similarly, when the state of the same photovoltaic array at different times is evaluated,
first, the contribution values w of k feature parameters are calculated o The calculation formula is as follows:
l 1 ≠l 2 and l 1 ,l 2 ＝2,…,m+1，
Wherein l 1 ，l 2 Indicating the different scenarios to be evaluated and,
then, a positive difference matrix E is calculated + ＝Y + W and a negative difference matrix E - ＝Y - W, where the disparity vector of the normalized feature parameters is w = (w) 1 ,w 2 ,…,w k ) And is made of
The positive and negative difference matrices are expressed as follows:
then, the forward projection coefficient of the t-th characteristic parameter of the s-th scheme to be evaluated projected to the t-th characteristic parameter of the positive ideal evaluation scheme and the negative projection coefficient of the t-th characteristic parameter of the s-th scheme to be evaluated projected to the t-th characteristic parameter of the negative ideal evaluation scheme are respectively:
wherein the content of the first and second substances, the value of the t characteristic parameter of the positive ideal evaluation scheme is indicated, wherein t =1,2, \8230;, k;the method is characterized by comprising the following steps of (1) referring to the tth characteristic parameter value of the tth scheme to be evaluated, wherein s =2,3, \ 8230;, m, m +1;
the t characteristic parameter of negative ideal evaluation schemeValues, where t =1,2, \8230;, k;the method is characterized by comprising the following steps of (1) referring to the tth characteristic parameter value of the tth scheme to be evaluated, wherein s =2,3, \ 8230;, m, m +1;
calculating a positive and negative difference projection matrix Q + 、Q - The calculation formulas are respectively as follows:
then, calculating Euclidean distances of each scheme to be evaluated relative to the positive and negative ideal evaluation schemes as follows:
calculating the optimal distance D s Wherein s is a scheme to be evaluated, and the calculation formula is as follows:
in the same way, according to the optimal distance D s And judging the states of the same photovoltaic array at different moments.
And finally, establishing a time function relation between the state evaluation result and each longitudinal and transverse parameter, wherein the time function relation comprises an irradiance-state evaluation value curve, an assembly backboard temperature-state evaluation value curve, an assembly mismatch rate-state evaluation value curve, a dust deposition rate-state evaluation value curve and the like. By establishing a time function relationship, the running states of the same array in different time periods can be longitudinally compared, and the running states of different arrays in the same time period can be transversely compared.
The curve fitting is to select an appropriate curve type to realize the curve fitting of the monitored object, and analyze the relation between two variables by using a fitted curve equation. In the implementation, according to the principle of the least square method, a Gaussian fitting method with high fitting degree is adopted, and the expression is as follows:
in the formula, the parameter y to be estimated max 、x max The physical meanings represented by s are the peak value, peak position and half width information of the Gaussian curve.
As shown in table 1, the photovoltaic array status types include five categories, normal, shadow, dust, fault, and aging. By the method, the longitudinal angle is combined with an I-V curve (a curve of current and voltage generated by the photovoltaic array) and an irradiance curve, the operating state curve (represented by the optimal distance degree) of a certain photovoltaic array in the same time period is analyzed, the abnormal reason is analyzed, and an operation and maintenance decision is provided. In implementation, when the photovoltaic array is under uniform illumination, the state evaluation value is low (i.e. lower than a set value), the I-V curves of each group of strings of the photovoltaic array are consistent (i.e. the functional relationship satisfied by the I-V curves of each group of strings is the same), and the power curve is slowly and continuously reduced in a time sequence, so that the increase of dust accumulation of the photovoltaic array can be judged, and an operation and maintenance suggestion that the photovoltaic array needs to be cleaned urgently is given.
The lateral angle can be analogous to the operation of different arrays in the same time period. In the implementation, the photovoltaic arrays a and B are taken as an example. When the optimal distance between the photovoltaic arrays A and B is 0.832 and 0.576 respectively, and the I-V curve and the irradiance curve of the photovoltaic arrays A and B in the same time period are basically the same, comparing the characteristic parameters, if the component back plate temperature of B is higher than that of A, then dividing into two cases: if the on-stream time A of A is t On-stream time B greater than B t If B has local hot spot, then B needs to be checked in time; if A is t <B t And judging that the component aging condition exists in the component B.
TABLE 1
Parts of the specification not described in detail are known in the art or are common general knowledge in the field.
The specific embodiments are given above, but the present invention is not limited to the described embodiments. The basic idea of the present invention lies in the above basic solution, and it is not necessary for those skilled in the art to expend creative efforts to design various modified models, formulas and parameters according to the teaching of the present invention. Variations, modifications, substitutions and alterations may be made to the embodiments without departing from the principles and spirit of the invention, and still fall within the scope of the invention.
Claims (9)
1. A photovoltaic array state judgment method is characterized by comprising the following steps:
(1) Collecting characteristic parameters influencing the state of each photovoltaic array;
(2) Introducing time sequence nodes and photovoltaic array monitoring points, establishing a parameter model from two dimensions of transverse dimension and longitudinal dimension, and expressing the parameter model by using a characteristic parameter matrix as follows:
wherein: r is ij ＝[R ij1 、R ij2 …R ijk ]；R m×n Representing m multiplied by n schemes to be evaluated for a longitudinal and transverse dimension characteristic parameter matrix; m: the number of the selected time sequence nodes; n: the number of the selected photovoltaic array monitoring points is determined; i: an ith time series node; j: the jth photovoltaic array monitoring point; r ij : monitor point j atThe characteristic parameter set at the time of the time node i represents a scheme to be evaluated; r ijk : a kth characteristic parameter of the jth photovoltaic array at i time nodes; k: the number of the characteristic parameters;
(3) Constructing a photovoltaic array running state evaluation model based on a positive ideal point evaluation scheme and a negative ideal point evaluation scheme;
(4) And establishing a time function relation between the state evaluation result and each longitudinal and transverse parameter by adopting a Gaussian curve fitting method, and evaluating the current state of the photovoltaic array from two angles of longitudinal and transverse directions by combining the array I-V curve and the irradiance-temperature curve.
2. The method according to claim 1, wherein the characteristic parameters include: irradiance, ambient temperature, component backplane temperature, component mismatch rate, shadow rate, dust deposition rate, aging rate, failure rate.
3. The method for judging the state of the photovoltaic array according to claim 1, wherein the step (3) is specifically as follows:
1) Constructing a positive ideal point state evaluation matrix and a negative ideal point state evaluation matrix;
2) Calculating the contribution value, and constructing a positive difference matrix and a negative difference matrix according to the contribution value;
3) Calculating a projection coefficient, and constructing a positive and negative difference projection matrix according to the projection coefficient;
4) And calculating the optimal distance of each scheme to be evaluated, and then evaluating the running state of the photovoltaic array in each scheme to be evaluated.
4. The method for judging the state of the photovoltaic array according to claim 3, wherein the step 1) is specifically as follows:
firstly, a state matrix X to be evaluated of different photovoltaic arrays at a certain moment is selected n×k The method comprises the following steps:
wherein n represents the number of photovoltaic arrays, and k represents the number of characteristic parameters;
selecting a photovoltaic array and a state matrix Y to be evaluated at different moments m×k The method comprises the following steps:
wherein m is the number of time points of data acquisition on a time axis, and k represents the number of characteristic parameters;
then, for matrix X n×k Constructing a positive and negative ideal point state evaluation matrix X + 、X - : said X + In, the first row data is AND X n×k Corresponding positive ideal evaluation scheme, and the rest is the matrix X n×k (ii) a Said X is - In, the first row data is AND X n×k Corresponding negative ideal evaluation scheme, and the rest is the matrix X n×k ；
For matrix Y n×k Constructing a positive and negative ideal point state evaluation matrix Y + 、Y - : said Y is + In the first row, the data is Y m×k Corresponding positive ideal evaluation scheme, and the rest is the matrix Y m×k (ii) a Said Y - In, the first row data is and Y m×k Corresponding negative ideal evaluation scheme, the rest being the matrix Y m×k ；
The positive ideal evaluation scheme is an evaluation scheme that all characteristic parameters simultaneously take the best values, and the negative ideal evaluation scheme is an evaluation scheme that all characteristic parameters simultaneously take the worst values.
5. The method for judging the state of the photovoltaic array according to claim 4, wherein the step 2) is specifically as follows:
a) When the state evaluation is carried out on different photovoltaic arrays at the same time:
first, the contribution values w of k feature parameters are calculated j The calculation formula is as follows:
l 1 ≠l 2 and l 1 ,l 2 ＝2,…,n+1，
Wherein i 1 ，i 2 Indicating the different scenarios to be evaluated and,
then, a positive difference matrix E is calculated + ＝X + W, and a negative difference matrix E - ＝X - W, where the disparity vector of the normalized feature parameters is w = (w) 1 ,w 2 ,…,w k ) And is made ofThe positive and negative difference matrices are expressed as follows:
b) When evaluating the state of the same photovoltaic array at different times:
first, the contribution values w of k feature parameters are calculated o The calculation formula is as follows:
l 1 ≠l 2 and l 1 ,l 2 ＝2,…,m+1，
Wherein l 1 ，l 2 Representing the different scenarios to be evaluated,
then, the user can use the device to perform the operation,computing a positive difference matrix E + ＝Y + W, and a negative difference matrix E - ＝Y - W, where the disparity vector of the normalized feature parameters is w = (w) 1 ,w 2 ,…,w k ) And is made ofThe positive and negative difference matrices are expressed as follows:
6. the method for judging the state of the photovoltaic array according to claim 5, wherein the step 3) is specifically as follows:
a) When the state evaluation is carried out on different photovoltaic arrays at the same time:
firstly, the forward projection coefficient of the t-th characteristic parameter of the s-th scheme to be evaluated projected to the t-th characteristic parameter of the positive ideal evaluation scheme and the negative projection coefficient of the t-th characteristic parameter of the s-th scheme to be evaluated projected to the t-th characteristic parameter of the negative ideal evaluation scheme are respectively as follows:
wherein, the first and the second end of the pipe are connected with each other, the value of the t characteristic parameter of the positive ideal evaluation scheme is indicated, wherein t =1,2, \8230;, k;the method is characterized by comprising the following steps of (1) referring to the tth characteristic parameter value of the tth scheme to be evaluated, wherein s =2,3, \8230, n, n +1;
the value of the t characteristic parameter of the negative ideal assessment scheme is indicated, wherein t =1,2, \8230;, k;
the method is characterized by comprising the following steps of (1) referring to the tth characteristic parameter value of the tth scheme to be evaluated, wherein s =2,3, \ 8230;, n, n +1;
then, a positive and negative difference projection matrix P is calculated + 、P - The calculation formulas are respectively as follows:
b) When the state of the same photovoltaic array at different times is evaluated:
firstly, the forward projection coefficient of the t-th characteristic parameter of the s-th scheme to be evaluated projected to the t-th characteristic parameter of the positive ideal evaluation scheme and the negative projection coefficient of the t-th characteristic parameter of the s-th scheme to be evaluated projected to the t-th characteristic parameter of the negative ideal evaluation scheme are respectively as follows:
wherein the content of the first and second substances, the method refers to the value of the t characteristic parameter of an ideal evaluation scheme, wherein t =1,2, \8230;, k;the method is characterized by comprising the following steps of (1) referring to the tth characteristic parameter value of the tth scheme to be evaluated, wherein s =2,3, \ 8230;, m, m +1;
the value of the t characteristic parameter of the negative ideal assessment scheme is indicated, wherein t =1,2, \8230;, k;
the method is characterized by comprising the following steps of (1) referring to the tth characteristic parameter value of the tth scheme to be evaluated, wherein s =2,3, \8230, m, m +1;
then, a positive and negative difference projection matrix Q is calculated + 、Q - The calculation formulas are respectively as follows:
7. the method for judging the state of the photovoltaic array according to claim 6, wherein the step 4) is specifically as follows:
a) When the state evaluation is carried out on different photovoltaic arrays at the same time:
firstly, calculating Euclidean distances of each scheme to be evaluated relative to positive and negative ideal evaluation schemes as follows:
then, an optimum distance D is calculated s Wherein s is a scheme to be evaluated, and the calculation formula is as follows:
finally, according to the optimal distance D s Performing state evaluation on different photovoltaic arrays at the same time;
b) When the state of the same photovoltaic array at different times is evaluated:
firstly, calculating Euclidean distances of each scheme to be evaluated relative to positive and negative ideal evaluation schemes as follows:
then, an optimum distance D is calculated s Wherein s is a scheme to be evaluated, and the calculation formula is as follows:
finally, according to the optimal distance D s And carrying out state evaluation on the same photovoltaic array at different moments.
8. The method for determining the state of a photovoltaic array according to claim 1, wherein in the step (4), the time function relationship comprises an irradiance-state evaluation value curve, a component backplane temperature-state evaluation value curve, a component mismatch rate-state evaluation value curve, and a dust accumulation rate-state evaluation value curve.
9. The method according to claim 7, wherein in the step (4), the evaluating the current state of the pv array from two vertical and horizontal angles specifically comprises: at the longitudinal angle: when the photovoltaic array is under uniform illumination, if the state evaluation value is lower than a set value, the I-V curves of all the groups of strings of the photovoltaic array meet the same functional relation, and the power curve under the time sequence is a continuously reduced curve, the dust accumulation of the photovoltaic array is judged to be increased; at the transverse angle: when the optimal distance between the photovoltaic arrays A and B is 0.832 and 0.576 respectively, and the I-V curve and irradiance curve of the photovoltaic arrays A and B are the same in the same time period, if the component backplane temperature of B is higher than that of A, and if the on-stream time of A is A t On-stream time B greater than B t B, local hot spot phenomenon occurs; if A is t <B t Then B has a component aging condition.
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