CN114721462B - Method for dynamically tracking maximum power point of photovoltaic array based on cloud model - Google Patents
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Abstract
The invention discloses a method for dynamically tracking the maximum power point of a photovoltaic array based on a cloud model, and belongs to the technical field of calculation, reckoning or counting. The method comprises the following steps: analyzing the distribution characteristics of the laser dynamic tracking sighting device by adopting a mathematical statistic method and establishing a distribution model; connecting a plurality of photovoltaic modules by a TCT structure which is connected in parallel and then in series, and analyzing the position relation between tracking and aiming precision and the global maximum power point of a system; based on the statistical distribution characteristic of dynamic tracking aiming, the GMPPT technology for simplifying the multi-peak power voltage characteristic into the dual-peak power voltage characteristic is provided by combining the output characteristic of the photovoltaic array at the mobile receiving end, and the purposes of reducing the voltage search interval and saving the system response time are achieved. The invention realizes the rapid searching of the global maximum power point of the system under the condition that the laser transmitting end and the receiving end move relatively, widens the application range, reduces the cost, improves the searching speed and simultaneously ensures the accuracy of global maximum power tracking.
Description
Technical Field
The invention discloses a method for dynamically tracking the maximum power point of a photovoltaic array based on a cloud model, and belongs to the technical field of calculation, reckoning or counting.
Background
Laser Power Transmission (LPT) is a technology for transmitting wireless Power over a long distance by using Laser as a carrier based on the photovoltaic effect. Because the laser has the characteristics of high power density, good directivity, high brightness and good monochromaticity, the volume and the quality of equipment required by the laser wireless energy transmission system are small, and the laser wireless energy transmission system does not interfere with signals of satellites in different rows, and is suitable for providing an energy acquisition means with advanced technology and flexible application for mobile equipment or platforms such as aircrafts, satellites, deep hole detectors, wireless sensor networks and the like, so the laser technology is one of the research hotspots at home and abroad at present and has wide development prospects in the aspects of military, aerospace, production and life and the like.
The general structure of the laser wireless energy transmission system is shown in fig. 1, and mainly comprises a laser emitting end, a free space and a laser receiving end. The laser receiving end is an important component of the LPT system and is used for converting received optical energy into electric energy of direct current, and the direct current electric energy is transmitted to the receiving end to supply energy to a load. The receiving end mainly includes: the photovoltaic system comprises a photovoltaic array, a photovoltaic converter, a direct current load and a corresponding control system, wherein the light-electricity conversion efficiency of the photovoltaic array is crucial to the whole system. Because the laser has gaussian characteristics and the LPT technology is generally applied to the situation where the relative mobility of the transceiving end is strong, the irradiation intensity on the photovoltaic array changes frequently, so that the light intensity of the incident panel changes, the volt-ampere output curve of the photovoltaic array at the mobile receiving end changes accordingly, the stable output of power is affected, and the light-electricity conversion efficiency of the photovoltaic array is greatly affected, so that the LPT system has a high requirement on the GMPPT tracking speed. Therefore, a GMPPT (Global Maximum Power Point Tracking) technology capable of quickly Tracking and improving the laser energy utilization rate under the condition of non-uniform dynamic energy distribution is needed.
Disclosure of Invention
The invention aims to provide a method for dynamically tracking the maximum power point of a photovoltaic array based on a cloud model, which aims at the defects of the background technology, and provides an optimized double-peak GMPPT technology by adopting a mathematical statistics method to analyze and establish a distribution model for the characteristic analysis of the laser dynamic tracking aiming technology, analyzing the overall law of the power characteristic of the photovoltaic array at a receiving end under the electrical connection of a complete Cross structure (TCT, total-Cross-Tie) of the photovoltaic array, thereby greatly shortening the response time of the system, improving the search speed and solving the key technical problems of slow response time, unstable power output and low photoelectric conversion efficiency of the conventional LPT system.
The invention adopts the following technical scheme for realizing the aim of the invention:
a method for dynamically tracking the maximum power point of a photovoltaic array based on a cloud model comprises the following 3 steps.
testing the tracking and aiming positions of various existing tracking and aiming devices, recording the position deviation between the tracking and aiming points and the preset target point by taking the preset target point as a reference point, drawing a position deviation distribution characteristic curve, and performing fitting verification on the position deviation distribution characteristic curve by using a nonparametric testing method in mathematical statistics to obtain the conclusion that the position deviation distribution characteristic curve of the dynamic laser tracking and aiming device accords with the distribution of a cloud model, and finally obtaining the conclusion that the position deviation distribution characteristic curve of the dynamic laser tracking and aiming device accords with the distribution of the cloud modelConforming to normal cloud '3E' according to cloud model n The characteristic of the rule is that the dynamic tracking of the maximum power point of the photovoltaic array is converted into the tracking of the maximum power point of the photovoltaic module at a fixed position. Expectation E of cloud model x Is composed of
Entropy E n Is composed of
Hyper entropy H e Is composed of
the method is characterized in that for branches formed by connecting different parallel branches in series, diodes are connected in parallel on each parallel branch, the irradiation change can be automatically adapted, the maximum power point positions of the photovoltaic arrays in different scales are related to the scales of the photovoltaic arrays based on the cloud model distribution characteristics of the position deviation distribution characteristic curve of the tracking sighting device and MATLAB simulation, and the voltages corresponding to the maximum power points of the photovoltaic arrays in different scales are in direct proportion to the open-circuit voltages of the photovoltaic arrays. The voltage range of the maximum power point is different for different laser irradiation conditions.
Sequencing local maximum power points on a TCT photovoltaic array curve according to the voltage magnitude sequence, obtaining per unit irradiation intensity of each photovoltaic module according to a laser energy distribution simplified model, deriving a power per unit value expression of the local maximum power points by taking a first local maximum power point as a reference, obtaining a serial number value of the local maximum power point closest to the maximum power point according to the fact that the derivative of the power per unit value expression of the local maximum power point to the local maximum power point serial number is zero, and determining a voltage searching range according to the obtained serial number value of the local maximum power point.
When the scale n of the photovoltaic array is odd, the numerical value of the local maximum power point closest to the maximum power point is
The voltage search range of the maximum power point is [ V ] ref_start ,V ref_finish ]，V ref_start ＝(2[k]-1)*0.76*V oc ，V ref_finish ＝(2[k]+1)*0.76*V oc K is the kth local maximum power point, when k is an integer, the kth local maximum power point is the global maximum power point, when k is not an integer, the global maximum power point is at the [ k ] th]Local maximum power point and k]+1 local maximum power points.
When the photovoltaic array scale n is an even number, the numerical value of the local maximum power point closest to the maximum power point is
The voltage search range of the maximum power point is V ref_start ,V ref_finish ]，V ref_start ＝(2[k])*0.76*V oc ，V ref_finish ＝(2[k]+2)*0.76*V oc 。
And 3, optimizing the traditional GMPPT technology for scanning a voltage full range into the GMPPT technology for scanning a voltage interval range constructed by two local maximum power points closest to the maximum power point based on the statistical distribution characteristic of the dynamic tracking aiming position deviation and by combining the power characteristic of the photovoltaic array at the mobile receiving end, thereby achieving the purpose of increasing the GMPPT tracking speed. The method comprises the following steps: firstly, determining voltages corresponding to two adjacent local maximum power points according to the scale of the photovoltaic array to construct a voltage search range of the maximum power point, then adjusting the output voltage of the photovoltaic array to be in the voltage range by adopting a voltage positioning algorithm, and finally adjusting the duty ratio of a direct current converter connected behind the photovoltaic array to perform disturbance observation on the output signal of the direct current converter until the photovoltaic array works at the maximum power point.
According to the output characteristic analysis of the photovoltaic array power voltage of the receiving end, an actively controlled Boost converter is added behind the photovoltaic array, and the global maximum power point tracking technology of positioning firstly and then scanning is realized by using a chip.
By adopting the technical scheme, the invention has the following beneficial effects:
(1) Performance advantages are as follows: compared with the situation that the receiving end is fixed, the method aims at the practical application that the load at the receiving end moves rapidly, and obtains a key conclusion that the probability that the tracking aiming can accurately aim at one time in a dynamic LPT system is approximately 100 percent according to the dynamic tracking aiming characteristic, all possibilities occurring dynamically are simplified into the fixed irradiation situation, and the method adopts the maximum power point tracking technology of double-peak voltage interval searching aiming at the fixed irradiation situation. Compared with the traditional GMPPT method for tracking the whole voltage range, the method provided by the invention reduces the voltage search interval and saves the system response time, which means that the proposed double-peak GMPPT technology can more quickly and accurately track the maximum power point of the LPT system. Meanwhile, the invention provides an optimized GMPPT technology based on the aiming distribution characteristics of the tracking sighting device, combines mathematical and statistical disciplines into engineering application, can adapt to various occasions where the transmitting and receiving ends are not relatively static in laser wireless energy transmission, has enhanced applicability and universality.
(2) The cost advantage is as follows: compared with the prior art that the research is based on the situation that the receiving end is relatively fixed, the method is suitable for the situation that the receiving end is in a moving state in the laser wireless energy transmission, avoids the need of designing different searching methods aiming at different situations, has wide application range, and saves time and cost.
(3) Modularization and easy integration: the scheme provided by the invention is beneficial to modularization realization, the development of hardware circuits, chips and the like which are specifically realized in the communication field is mature, and the subsequent chip design is easy to realize.
Drawings
Fig. 1 is a general configuration diagram of a laser wireless energy transfer system.
Fig. 2 is a block diagram of an example of dynamic laser tracking targeted wireless power transfer.
Fig. 3 is a schematic diagram of the deviation of the tracked aim position from the target point under dynamic tracking.
FIG. 4 is a schematic diagram of a two-dimensional normal cloud model.
FIG. 5 is a block diagram of a one-dimensional normal cloud generator.
FIG. 6 is "3E" of a normal cloud n "rule graph.
Fig. 7 (a) is a structural view of the electrical connection of the photovoltaic array SP.
Fig. 7 (b) is a diagram of the electrical connection structure of the photovoltaic array TCT.
FIG. 8 (a) is a graph showing the power output characteristics of the 5 × 5 PV array elements 6# to 20# at the laser tracking aiming position, fig. 8 (b) is a graph of power output characteristics of 5 × 5 pv arrays 1# to 5# array elements and 21# to 25# array elements at the laser tracking aiming position.
Fig. 9 (a) is a schematic diagram of a voltage search range in the conventional MPPT method, and fig. 9 (b) is a schematic diagram of a voltage search range in the dual-peak GMPPT method.
Fig. 10 is a flow chart of voltage location.
Fig. 11 is a schematic diagram of finding the maximum power point by the perturbation and observation method.
Fig. 12 is an algorithm flow diagram of a global maximum power point tracking technique.
Detailed Description
The technical scheme of the invention is explained in detail in the following with reference to the attached drawings.
The invention provides a method for dynamically tracking the maximum power point of a photovoltaic array based on a cloud model, which is further described in detail with reference to the attached drawings in order to make the purpose, the technical scheme and the effect of the invention clearer and clearer.
1. Laser dynamic tracking aiming technical characteristic modeling
(1) Establishing cloud model for tracking sighting characteristics of sighting device
In order to make the laser wireless energy transmission system suitable as usual and maximize the photoelectric conversion efficiency of the receiving end under the condition that the receiving end moves rapidly, the characteristics of the tracking and aiming technology need to be researched. In the application, the receiving end has the characteristics of flexibility, high efficiency, safety and the like (such as an unmanned aerial vehicle), and has unique advantages in reconnaissance and target locking in occasions such as specific battlefield anti-terrorism and the like. The dynamic laser tracking aiming wireless energy transmission example is shown in fig. 2 and mainly comprises a laser transmitting end and a laser receiving end. At a laser emission end, an unmanned aerial vehicle image is captured through a television viewing window, the central position of a laser battery panel is extracted through information processing, and a servo tracking module is driven, so that the laser battery panel is positioned at the center of a television viewing field. The laser emission axis is parallel to the television viewing axis, and emits laser through the laser emission window to irradiate on the laser charging battery panel. At the laser receiving end, the laser charging battery board converts laser into electric energy. The accuracy of the dynamic tracking and aiming technique is particularly important.
Therefore, in order to find out the inherent law of tracking and aiming, the randomness, the ambiguity and the relevance in the tracking and aiming process are uniformly depicted by endowing the sample points with random certainty on the basis of combining probability theory and fuzzy mathematical theory. The deviation between the position aimed by the tracking sighting device and the optimal aiming point in the research process is described by utilizing 3 digital characteristics (expectation, entropy and super entropy), and an uncertain conversion model between qualitative and quantitative concepts expressed by the digital characteristics is formed by a specific algorithm. Due to the influence of various random factors, the tracking sighting device does not aim at the optimal aiming point every time, and the positions of multiple aiming are approximately normally distributed on the target photovoltaic array as shown in fig. 3. Therefore, a normal cloud model (E) as shown in FIG. 4 is used x ，E n ，H e ) To describe the overall tracking aiming condition; the expected value is the coordinate of the average point of all cloud droplets (tracking points) on the photovoltaic array, and reflects the target performance of the tracking sighting device on the target point; the entropy reflects randomness of a tracking point, namely the discrete degrees of the tracking point to an expected value in the horizontal direction and the vertical direction, and reflects ambiguity of the tracking, namely membership; the super entropy reflects the discrete degree of the entropy and embodies the uncertainty of the membership degree.
(2) Tracking aiming distributed cloud drop generation algorithm
Clouds are models of uncertainty transitions between qualitative concepts and quantitative, expressed in natural language values. By expected value E x Entropy E n Hyper entropy H e The three values represent the numerical characteristics of the cloud. Thus, to quantitatively analyze the distribution of the tracking aim characteristics of the tracking sight, a tracking aiming cloud droplet is generated by a one-dimensional inverse cloud generator as shown in fig. 5:
1) By making a reservationThe target point is used as a reference point, and the position information x of the experimental sample point (namely the tracking aiming point) is recorded and input i (i＝1,2,…,m)。
2) According to x i Calculating the mean of the samples for the set of data
First order sample absolute center moment
Sample variance
3) Calculating expectation
Entropy of the stress
Super entropy
4) And drawing a tracking aiming distribution curve chart by combining the calculated digital characteristics, as shown in figure 6.
Based on a distribution characteristic model and a fuzzy correlation theory, which have been defined by probability theory, a non-parameter test method is adopted to fit a tracking aiming distribution curve graph, and a distribution model of tracking aiming distribution is verified. And the test result shows that the tracking and aiming distribution curve is completely fitted with the cloud model curve, so that the tracking and aiming can be obtained to meet the cloud model distribution characteristic.
Based on the above conclusions, it can be obtained by combining statistical knowledge that the cloud model has the following rules: 99.74% of cloud drops fall on (E) x -3E n ，E x +3E n ) Within the range, even negligible (E) x -3E n ，E x +3E n ) Quantitative values outside the interval, i.e. "3E" of normal cloud as shown in FIG. 6 n "rule. Research shows that the aiming characteristics of the tracking sighting device meet the distribution of a cloud model,and it conforms to "3E" of a normal cloud n "rule. Based on the distribution characteristic of tracking aiming, the method lays a foundation for the subsequent research range of dynamic tracking aiming of the laser in the LPT system, and avoids a large amount of invalid and complex condition analysis. The invention conforms to normal cloud 3E by utilizing tracking aiming characteristics n The characteristic of the rule is that the dynamic tracking aiming is simplified into a specific fixed tracking aiming, and an optimized GMPPT method is designed based on the simplified fixed tracking aiming.
2. Power characteristic analysis after TCT connection of photovoltaic array
(1) Analysis of TCT connection mode: under the condition of Gaussian laser irradiation with uneven energy distribution, the most main reason for influencing the output power of the photovoltaic array is caused by mismatching of the output characteristics of each photovoltaic cell in the array. In most of the research on the LPT system, mismatch loss in the array is reduced mainly by optimizing the electrical connection mode of the photovoltaic array, so as to achieve the purpose of improving the output power of the array. In practical applications, it is common to have an SP connection as shown in fig. 7 (a) and a TCT connection as shown in fig. 7 (b). In the TCT connection, because the battery monomers are not simply connected in series and in parallel, the current generated by each battery monomer flows out in a plurality of directions, so that the work of other batteries in the same branch is not influenced when the illumination of a certain battery monomer is different, and the structure can better solve the problem of power loss caused by mismatching among photovoltaic batteries when the illumination is uneven, so that the power characteristic analysis is carried out on the TCT structure.
(2) Analyzing the power characteristics of the TCT connection photovoltaic array: the output characteristics of the photovoltaic array of the TCT connection are derived from the power characteristics of the individual photovoltaic modules. If the photovoltaic array is of an nxn scale, if n is an odd number, the center of the Gaussian laser spot (namely the origin of a photovoltaic array coordinate system) is superposed with the photovoltaic cell monomer at the center of the photovoltaic array; if n is an even number, the center of the Gaussian laser spot does not coincide with any photovoltaic cell monomer in the photovoltaic array. Therefore, the output characteristics of the photovoltaic array under gaussian laser irradiation when n is an odd number will be discussed first.
When n is an odd number, a rectangular coordinate system is established by taking the center of a laser spot as an origin, and the ratio X of the irradiation intensity of Gaussian laser can be expressed mathematically as:
wherein G is i,j Is the intensity of irradiation of the photovoltaic cell with coordinates (i, j), D i,j Distance of the photovoltaic cell to the center of the spot, G 0,0 Is the intensity of irradiation at the center of the laser spot, w 0 Is the radius of the laser spot.
The method comprises the steps of sequentially naming local maximum power points on a photovoltaic string P-V curve as LMPP1, LMPP2, \8230, LMPPk 8230and 8230in the order of voltage from small to large, recording the irradiation intensity of the origin of a photovoltaic array coordinate system as reference 1, and obtaining the per-unit irradiation intensity of each photovoltaic cell in a photovoltaic array according to a laser energy distribution simplified model. Since the short-circuit current of the photovoltaic module is proportional to the irradiation intensity, the ratio of the short-circuit current of the parallel branches is similar to equation (1). Recording the current of LMPP1 as reference 1, then the current per unit value I of LMPPk pk * Can be represented as follows, wherein X is represented by formula (3):
it is known that the voltage of each local peak point of a photovoltaic array under non-uniform illumination is equal to about an integer multiple of 0.76Voc, and therefore the voltage of each local peak point is about 0.76V oc ,3*0.76V oc ,5*0.76V oc ,…,n*0.76V oc . The voltage of the LMPP1 is recorded as reference 1, and then the voltage per unit value V of the LMPPk pk * Can be expressed as:
V pk * ＝2k-1 (4)
if the power P of LMPP1 is reduced p1 Recording as benchmark 1, the output of LMPPkPer unit value P of output power pk * Can be expressed as:
deriving k and making it 0 yields the following equation:
similarly, by deriving the photovoltaic array with n being an even number, the expression of k can be obtained as follows:
therefore, in the formula (6) and the formula (7), if the value of k is a positive integer, the kth local maximum power point LMPPk is GMPP; if k is not an integer, GMPP is between LMPP [ k ] and LMPP ([ k ] + 1). Where [ k ] represents the rounding of k.
The location of the GMPP is only dependent on the photovoltaic array scale and not on the laser irradiance. Therefore, under the condition of the fixed receiving end photovoltaic array, the GMPP position of the receiving end photovoltaic array has constancy. However, if the laser irradiation deviates from the central target aiming point to a great extent, the irradiation condition of the photovoltaic array is greatly different, wherein the property of the GMPP corresponding to the kth LMPP is not changed, and the voltage of the kth LMPP corresponding to the GMPP is changed. In a 5 x 5 scale photovoltaic array, the first case: when the center of the spot falls within the shaded pv modules 6# to 20# in fig. 8 (a), GMPP corresponds to the second LMPP, which corresponds to a voltage of 3 × 0.76v oc (ii) a In the second case: when the light spot falls on the shaded pv modules 1# to 5# and 21# to 25# in fig. 8 (b), the GMPP still corresponds to the second LMPP, but the corresponding voltage is 2 × 0.76v oc The difference between the two voltage values is large, the voltage searching range cannot be kept constant, and the rapid and accurate dual-peak GMPPT technology is inconvenient to follow. But based on the above modeling of the characteristics of the dynamic tracking and aiming technique of the laser, the tracking and aiming device is discoveredAiming characteristics meet cloud model distribution, 99.74% of tracking aiming can realize aiming of the first condition, and the possibility of the second condition can be completely ignored, so that the GMPP position range and the corresponding voltage can be calculated through a mathematical expression aiming at the fixed photovoltaic array scale, and a theoretical basis is provided for the subsequent optimization of the traditional GMPPT technology.
3. Dual-peak global maximum power point tracking algorithm analysis
According to simulation and experimental experience, the Boost circuit is used as an active direct-current converter to adjust the final output power. As shown in FIG. 1, the photovoltaic modules TCT are connected and then connected in parallel to the input end of the Boost circuit, and the output end of the Boost circuit is connected with the final direct current load R L The voltage and current of the input end and the output end of the Boost circuit are respectively collected, a voltage positioning algorithm and a disturbance observation method are carried out in a DSP (Digital Signal Processing) controller, the output voltage of the photovoltaic array can be adjusted to be in a voltage range closest to the global maximum power point, the maximum power point is tracked, and more efficient, faster and more accurate power point tracking is realized.
As can be seen from the above analysis, the non-uniform gaussian laser irradiation energy distribution causes a plurality of peak points to exist in the overall power characteristic curve, but in combination with the tracking and aiming condition for the dynamic changes of the photovoltaic arrays of different scales, the position of the global maximum power point relative to the local maximum power point is constant, the search range can be reduced to be between two local maximum power points, and then the global maximum power point is obtained by searching and comparing, as shown in fig. 9 (a) and 9 (b).
The method firstly calculates k related to the scale of the photovoltaic array through the power characteristics of the TCT structure photovoltaic array under dynamic laser tracking aiming so as to determine V ref The size of (2). And then, positioning the search voltage range from the original 0 to a certain local maximum power point voltage by a voltage positioning method. The voltage positioning flow chart is shown in fig. 10, and the positioning method is based on the dichotomy idea and aims to adjust the output voltage V of the photovoltaic array pvstring Adjusted to V ref . Because the open-circuit voltage of the photovoltaic cell can change along with the illumination intensityBut different so that the calculated V ref Is only an approximate value of the actual GMPP voltage, and only needs the adjusted V in order to accelerate the operation process of the voltage control subprogram pvstring At V ref In the present invention, the range may be set to (V) ref -1,V ref +1). When V is pvstring <V ref When-1, assign D to D max The dichotomy modifies D so that D becomes smaller, and V pvstring Enlarging; in the same way, when V pvstring >V ref When +1, assign D to D min D becomes larger after dichotomy, V ref Finally, will V pvstring Is adjusted to (V) ref -1,V ref + 1) range.
After the positioning is finished, the local maximum power point is searched by adopting a disturbance observation method. The disturbance observation method, as the name implies, needs to apply an external disturbance to the controlled circuit to generate a corresponding change in the output voltage, then samples the output voltage and the output power of the circuit to which the external disturbance is applied, and makes the next judgment after observing the change trends of the output voltage and the output power, and the working principle of the disturbance observation method is shown in fig. 11. The specific idea is as follows: disturbance is applied to an input signal of the converter by adjusting the Boost duty ratio D, if the applied disturbance causes the output voltage to increase and the output power to increase, as shown by P in the figure a Change to P b Then the direction of the disturbance is considered to be correct, so that continuing to apply a disturbance in the same direction causes the output voltage to continue to increase; if the applied disturbance causes the output voltage to increase, but the output power to decrease accordingly, as shown by P c Change to P d Then applying the perturbation in the reverse direction to reduce the output voltage; and vice versa. According to the idea, the values of the output voltage and the output current are detected at fixed time intervals, the control direction of the next step is determined according to the observation and comparison results, and the process is circulated until the output power approaches the maximum power point. Because the voltage searching range of the double-peak MPPT technology is greatly reduced, the tracking step length is set to be a small numerical value, so that the tracking speed can be increased, and the tracking precision can be improved.
V ref_start And V ref_finish The calculation is obtained by the DSP through an algorithm, and the specific algorithm flow is shown in FIG. 12. Given photovoltaic array size n in combination with practical application and open circuit voltage V of photovoltaic module oc Value assigned V ref_start Is 0, assigned a value of V ref_finish Is n x V oc That is, the default initial voltage search range is the maximum range in which the output voltage can be varied. And then n is classified into odd and even numbers, if n can be divided by 2, the n is an even number, otherwise, the n is an odd number. Assigning a corresponding mathematical expression to k and giving a starting point V of the voltage sweep range ref_start And endpoint V ref_finish I.e. maximum power point at k]A local maximum power point and a [ k ]]V between +1 local maximum power points, when n is odd number ref_start ＝(2[k]-1)*0.76*V oc ，V ref_finish ＝(2[k]+1)*0.76*V oc When n is an even number, V ref_start ＝(2[k])*0.76*V oc ，V ref_finish ＝(2[k]+2)*0.76*V oc And then tracking the maximum power point by the voltage positioning algorithm and the more accurate variable step size disturbance observation method.
The above embodiments are only for illustrating the technical idea of the present invention, and the protection scope of the present invention is not limited thereby, and any modifications made on the basis of the technical scheme according to the technical idea of the present invention fall within the protection scope of the present invention.
Claims (6)
1. A method for dynamically tracking the maximum power point of a photovoltaic array based on a cloud model is characterized in that,
establishing a cloud model for describing the distribution characteristics of the tracking aiming points, and conforming to the normal cloud 3E according to the cloud model n "regular features, transform dynamic tracking of maximum power point of photovoltaic array to tracking of maximum power point of fixed position photovoltaic module, expectation E of said cloud model x Is composed of
Entropy E n Is composed of
Hyper entropy H e Is composed of
Wherein,
to track the sample mean of the coordinates of the sighting point location,
x i i =1,2, \ 8230for the position coordinates of the ith tracking aiming point, m, m is the number of tracking aiming points,
first order sample absolute center moments, S, for tracking the position coordinates of the aiming point 2 In order to be the variance of the samples,
tracking the maximum power point of the fixed position photovoltaic module, firstly determining two adjacent local maximum power points according to the scale of the photovoltaic array, constructing a voltage search range of the maximum power point according to voltages corresponding to the two adjacent local maximum power points, then adjusting the output voltage of the photovoltaic array to be in the voltage search range by adopting a voltage positioning algorithm, and finally adjusting the duty ratio of a direct current converter behind the photovoltaic array to carry out disturbance observation on the output signal of the direct current converter until the photovoltaic array works at the maximum power point, wherein,
the specific method for determining two adjacent local maximum power points according to the photovoltaic array scale and constructing the maximum power point search range according to the voltages corresponding to the two adjacent local maximum power points comprises the following steps: sequencing local maximum power points on a TCT photovoltaic array curve according to the voltage sequence, obtaining per unit irradiation intensity of each photovoltaic module according to a laser energy distribution simplified model, deriving a power per unit value expression of the local maximum power points by taking a first local maximum power point as a reference, obtaining a serial number value of the local maximum power point closest to the maximum power point according to the fact that the derivative of the power per unit value expression of the local maximum power point to the serial number of the local maximum power point is zero, determining a voltage searching range according to the obtained serial number value of the local maximum power point,
the specific method for adjusting the output voltage of the photovoltaic array to be within the voltage search range by adopting the voltage positioning algorithm comprises the following steps: determining the value range [ D ] of the duty ratio of a DC converter connected behind a photovoltaic array min ,D max ]Sampling and recording the output voltage and the current duty ratio of the DC converter, wherein the output voltage of the DC converter is less than V ref When-1, the value of the current duty ratio is assigned to D max Then the current duty ratio is recalculated, and the output voltage of the DC converter is greater than V ref When +1, the value of the current duty ratio is given to D min Then recalculating the current duty ratio, repeatedly sampling and recording the output voltage of the DC converter, and then adjusting the operation of the current duty ratio until the output voltage of the DC converter is (V) ref -1,V ref + 1), wherein D max 、D min Upper and lower limits, V, of the duty cycle of a DC converter following a photovoltaic array ref For outputting a voltage reference, V, to the DC converter ref Determined according to the voltage search range of the maximum power point,
the specific method for adjusting the duty ratio of the direct current converter connected behind the photovoltaic array to perform disturbance observation on the output signal of the direct current converter comprises the following steps: the duty ratio of the DC converter is increased to apply disturbance to the input of the DC converter, the output signal of the DC converter is observed, when the output voltage and the output power of the DC converter are both increased, the duty ratio of the DC converter is continuously increased, and when the output voltage of the DC converter is increased but the output power is decreased, the duty ratio of the DC converter is decreased.
2. The method according to claim 1, wherein the power per unit value of the local maximum power point is expressed as：
Wherein, P pk * For the power per unit value of the kth local maximum power point,
and n is the scale of the TCT photovoltaic array.
3. The method for dynamically tracking the maximum power point of the photovoltaic array based on the cloud model as claimed in claim 2, wherein when n is an odd number, the numerical value of the local maximum power point closest to the maximum power point is defined as
4. The method for dynamically tracking the maximum power point of the photovoltaic array based on the cloud model as claimed in claim 2, wherein when n is an even number, the numerical value of the local maximum power point closest to the maximum power point is
5. The method for dynamically tracking the maximum power point of the photovoltaic array based on the cloud model as claimed in claim 3, wherein the voltage search range of the maximum power point is [ V ] ref_start ,V ref_finish ]，V ref_start ＝(2[k]-1)*0.76*V oc ，V ref_finish ＝(2[k]+1)*0.76*V oc Wherein V is ref_finish 、V ref_start Is the upper and lower limits, V, of the maximum power point voltage search range oc Is the open circuit voltage of the TCT photovoltaic array.
6. The method for dynamically tracking the maximum power point of the photovoltaic array based on the cloud model as claimed in claim 4, whereinIn that the voltage search range of the maximum power point is [ V ] ref_start ,V ref_finish ]，V ref_start ＝(2[k])*0.76*V oc ，V ref_finish ＝(2[k]+2)*0.76*V oc Wherein V is ref_finish 、V ref_start Is the upper and lower limits, V, of the maximum power point voltage search range oc Is the open circuit voltage of the TCT photovoltaic array.
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