CN116736929A - Photovoltaic string global maximum power point tracking method and system based on region segmentation - Google Patents
Photovoltaic string global maximum power point tracking method and system based on region segmentation Download PDFInfo
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Abstract
The invention discloses a photovoltaic string global maximum power point tracking method and system based on region segmentation, and relates to the technical field of photovoltaic power generation. Obtaining an output characteristic value of a photovoltaic string; the output characteristic values include a current-voltage value and a power-voltage value; extracting characteristic voltage point V in output characteristic value init And according to the current value and the characteristic voltage point V in the output characteristic value init Calculating to obtain multiple initial powers P init The method comprises the steps of carrying out a first treatment on the surface of the Multiple initial powers P init Constructing a power data set; determining a global maximum power point of the photovoltaic string according to the power data set; determining the photovoltaic module area where the photovoltaic module area is located according to the maximum power point; the maximum power point is tracked in real time in the photovoltaic module area. The invention improves the searching efficiency reaching the global maximum power point and realizes the output maximization under the condition of partial shadow shielding of the photovoltaic string.
Description
Technical Field
The invention relates to the technical field of photovoltaic power generation, in particular to a photovoltaic string global maximum power point tracking method and system based on region segmentation.
Background
Due to the instability of the external environment, the photovoltaic power generation system, particularly the distributed photovoltaic power generation system, is extremely easy to be influenced by the conditions of cloud layer movement, building shielding and the like, and the photovoltaic string is in a partially shadow shielding condition, so that the output characteristic curve of the photovoltaic string is in a multimodal state. In order to ensure that the output of the photovoltaic string is maximized, global maximum power point tracking (Global Maximum Power Point Tracking, GMPPT) is widely applied to a photovoltaic power generation system, so that the maximization of photovoltaic output energy is realized, and the overall efficiency of the system is further improved.
The traditional GMPPT algorithm based on global scanning needs to search most areas of the photovoltaic curve, redundant search points are introduced, and the convergence speed of the algorithm is reduced. The GMPPT scheme based on the intelligent algorithm needs to optimize the preset parameters or needs a large amount of training data to achieve the purpose of fast tracking, but can bring a large calculation burden to the system. The traditional model-based GMPPT scheme needs to accurately model the photovoltaic string, has high requirement on data calculation, and can introduce an illumination sensor and increase the system cost.
Disclosure of Invention
The embodiment of the invention aims to provide a method and a system for tracking a global maximum power point of a photovoltaic string based on region segmentation, which improve the searching efficiency of reaching the global maximum power point and realize the maximization of output under the condition of partial shadow shielding of the photovoltaic string.
In order to achieve the above object, the embodiment of the present invention provides the following solutions:
a photovoltaic string global maximum power point tracking method based on region segmentation comprises the following steps:
obtaining an output characteristic value of a photovoltaic string; the output characteristic value includes: current-voltage value and power-voltage value;
extracting a characteristic voltage point V in the output characteristic value init And according to the current value in the output characteristic value and the characteristic voltage point V init Calculating to obtain multiple initial powers P init The method comprises the steps of carrying out a first treatment on the surface of the The plurality of initial powers P init Constructing a power data set;
determining a global maximum power point of the photovoltaic group string according to the power data set; determining the photovoltaic module area where the maximum power point is located according to the maximum power point; and then tracking the maximum power point in real time in the photovoltaic module area.
Optionally, extracting the output characteristicCharacteristic voltage point V in value init The method specifically comprises the following steps:
nth characteristic voltage point V init,n The calculation formula of (a) is specifically as follows:
V init,n ＝[σ ccr +σ eq (n-1)]·V oc0 -(N m -n)·V bp ；
wherein sigma ccr For the coefficient, sigma, of the constant current region operation eq Is the equivalent working voltage of the photovoltaic module, V oc0 Is open circuit voltage of the photovoltaic module under standard test conditions, wherein the standard test conditions are 25 ℃ environment temperature and 1000W/m 2 The illumination intensity, the atmospheric mass AM 1.5; v (V) bp The turn-on voltage of the bypass diode of the photovoltaic module; n (N) m The individual photovoltaic modules form a photovoltaic string.
Optionally, the maximum power point maps a characteristic voltage point V in the output characteristic value init,max The specific calculation formula is as follows:
wherein n represents a characteristic voltage point V init Is a number of (3).
Optionally, tracking the maximum power point in real time in the photovoltaic module area specifically includes:
wherein V is pv,ref (t) is the reference voltage corresponding to the photovoltaic working point of the current disturbance interval, V pv,ref (t-1) is the reference voltage corresponding to the photovoltaic working point of the last disturbance interval, dV pv The characteristic voltage point V extracted for the current extraction time and the last extraction time init Is the difference of dP pv Initial power P extracted for current extraction time and last extraction time init Difference of V step Is the voltage step length; sign (x) is a sign function.
In order to achieve the above purpose, the embodiment of the present invention further provides the following solutions:
a photovoltaic string global maximum power point tracking system based on region segmentation, comprising:
the data acquisition module is used for acquiring the output characteristic value of the photovoltaic string; the output characteristic value includes: current-voltage value and power-voltage value;
the characteristic voltage point extraction module is connected with the data acquisition module and is used for extracting a characteristic voltage point V in the output characteristic value init And according to the current value in the output characteristic value and the characteristic voltage point V init Calculating to obtain multiple initial powers P init The method comprises the steps of carrying out a first treatment on the surface of the The plurality of initial powers P init Constructing a power data set;
the determining module is connected with the characteristic voltage point extracting module and is used for:
determining a global maximum power point of the photovoltaic group string according to the power data set; determining the photovoltaic module area where the maximum power point is located according to the maximum power point;
and the tracking module is connected with the determining module and used for tracking the maximum power point in real time in the photovoltaic module area.
Optionally, the characteristic voltage point extraction module includes:
a calculation unit for calculating an nth characteristic voltage point V init,n The method comprises the steps of carrying out a first treatment on the surface of the The calculation formula is specifically as follows:
V init,n ＝[σ ccr +σ eq (n-1)]·V oc0 -(N m -n)·V bp ；
wherein sigma ccr For the coefficient, sigma, of the constant current region operation eq Is the equivalent working voltage of the photovoltaic module, V oc0 Is open circuit voltage of the photovoltaic module under standard test conditions, wherein the standard test conditions are 25 ℃ environment temperature and 1000W/m 2 The illumination intensity, the atmospheric mass AM 1.5; v (V) bp The turn-on voltage of the bypass diode of the photovoltaic module; n (N) m The individual photovoltaic modules form a photovoltaic string.
Optionally, the determining module includes:
a mapping unit for mapping the characteristic voltage point V in the output characteristic value with the maximum power point init,max The specific calculation formula is as follows:
wherein n represents a characteristic voltage point V init Is a number of (3).
Optionally, the tracking module includes:
the maximum power point tracking unit is configured to track a maximum power point in real time in the photovoltaic module area, and specifically includes:
wherein V is pv,ref (t) is the reference voltage corresponding to the photovoltaic working point of the current disturbance interval, V pv,ref (t-1) is the reference voltage corresponding to the photovoltaic working point of the last disturbance interval, dV pv The characteristic voltage point V extracted for the current extraction time and the last extraction time init Is the difference of dP pv Initial power P extracted for current extraction time and last extraction time init Difference of V step Is the voltage step length; sign (x) is a sign function.
In the embodiment of the invention, the output characteristic value of the photovoltaic group string is obtained; the output characteristic value includes: current-voltage value and power-voltage value; the photovoltaic power generation system can be rapidly applied to the existing photovoltaic power generation system without adding an additional illumination sensor, and has higher cost efficiency. The feature area is divided only according to the information in the photovoltaic module data manual, so that the cost brought by system modeling is not required to be additionally increased, and efficient loading is realized.
Extracting characteristic voltage point V in output characteristic value init And according to the current value and the characteristic voltage point V in the output characteristic value init Calculating to obtain multiple initial powers P init The method comprises the steps of carrying out a first treatment on the surface of the Multiple initial powers P init Constructing a power data set;only the characteristic point extraction program is inserted into the existing maximum power point tracking controller, hardware or larger software modification is not needed, and the cost is effectively reduced.
Determining a global maximum power point of the photovoltaic string according to the power data set; and determining the photovoltaic group area where the photovoltaic group string is positioned according to the maximum power point, so as to judge the area where the global maximum power point of the photovoltaic group string is positioned under the condition of partial shadow shielding. The working point position of the photovoltaic string can be quickly switched to the region where the global maximum power point is located, and the maximum power point tracking is performed, so that the convergence speed of the global maximum power point is ensured, and the maximization of the output of the photovoltaic string is realized.
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In order to more clearly illustrate the embodiments of the present invention or the technical solutions of the prior art, the drawings that are needed in the embodiments will be briefly described below, it being obvious that the drawings in the following description are only some embodiments of the present invention, and that other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
Fig. 1 is a schematic flow chart of a tracking method of a global maximum power point of a photovoltaic string based on region segmentation according to an embodiment of the present invention;
FIG. 2 is a schematic diagram of constant current region and characteristic point voltage extraction according to an embodiment of the present invention; wherein FIG. 2 (a) is a photovoltaic string current I pv And voltage V pv Is a schematic diagram of the variation relationship of (a); FIG. 2 (b) shows the voltage change rates dI/dV and V pv Is a schematic diagram of the variation curve of (a);
fig. 3 is a control block diagram of a tracking method of a global maximum power point of a photovoltaic string based on region segmentation according to an embodiment of the present invention;
fig. 4 is a schematic diagram of an operation result of a photovoltaic string global maximum power point tracking method based on region segmentation under a static partial shadow shielding condition according to an embodiment of the present invention; wherein FIG. 4 (a) is the photovoltaic power P pv A working waveform diagram; FIG. 4 (b) shows the photovoltaic voltage V pv A working waveform diagram; FIG. 4 (c) shows the photovoltaic current I pv A working waveform diagram;
fig. 5 is a schematic diagram of an operation result of a photovoltaic string global maximum power point tracking method based on region segmentation under a dynamic partial shadow shielding condition according to an embodiment of the present invention;
FIG. 6 is a diagram comparing a photovoltaic string global maximum power point tracking method based on region segmentation with the prior art under the condition of static partial shadow shielding according to the embodiment of the present invention;
fig. 7 is a schematic structural diagram of a photovoltaic string global maximum power point tracking system based on region segmentation according to an embodiment of the present invention;
fig. 8 is a general control structure diagram of a photovoltaic string global maximum power point tracking system based on region segmentation according to an embodiment of the present invention.
Symbol description:
the characteristic voltage point extraction module comprises a data acquisition module-1, a characteristic voltage point extraction module-2, a determination module-3 and a tracking module-4.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
The invention aims to provide a photovoltaic string global maximum power point tracking method and system based on region segmentation, which are used for solving the problem of low searching efficiency of the existing global maximum power point.
In order that the above-recited objects, features and advantages of the present invention will become more readily apparent, a more particular description of the invention will be rendered by reference to the appended drawings and appended detailed description.
Fig. 1 illustrates an exemplary flow of the above-described photovoltaic string global maximum power point tracking method based on region segmentation. The steps are described in detail below.
Step 1: obtaining an output characteristic value of a photovoltaic string; the output characteristic value includes: current-voltage values and power-voltage values.
Step 2: extracting characteristic voltage point V in output characteristic value init And according to the current value and the characteristic voltage point V in the output characteristic value init Calculating to obtain multiple initial powers P init The method comprises the steps of carrying out a first treatment on the surface of the Multiple initial powers P init Constructing a power data set; the method specifically comprises the following steps:
nth characteristic voltage point V init,n The calculation formula of (a) is specifically as follows:
V init,n ＝[σ ccr +σ eq (n-1)]·V oc0 -(N m -n)·V bp ； (1)
wherein sigma ccr For coefficients operating in constant current region, sigma eq Is the equivalent working voltage of the photovoltaic module, V oc0 Is open circuit voltage of the photovoltaic module under standard test conditions, wherein the standard test conditions are 25 ℃ environment temperature and 1000W/m 2 The illumination intensity, the atmospheric mass AM 1.5; v (V) bp The turn-on voltage of the bypass diode of the photovoltaic module; n (N) m The individual photovoltaic modules form a photovoltaic string.
In one example, the characteristic voltage point V in the constant current region (Constant Current Region, CCR) is extracted init Can be concretely an initialization flow, and characteristic voltage points V in n constant current regions after the output characteristic region is divided by the initialization flow init ，(V init ∈[V init,1 ,V init,2 ,…,V init,n ]) Searching is carried out, and a constant current area where the global maximum power point (Global Maximum Power Point, GMPP) of the photovoltaic string is located is determined. In the initialization process, the acquisition of the characteristic voltage point Vinit is realized by adjusting the working point voltage of the photovoltaic string, and the characteristic voltage point V of the photovoltaic string in the initialization process is required to be acquired init Number N of photovoltaic modules in group string m And keep the same.
FIG. 2 is a graph showing the output characteristics of a string of three MSX-60 photovoltaic panels under a shadow mask condition, where I pv ，V pv The output current and the output voltage of the photovoltaic string are respectively. The CCR region marked in FIG. 2 is in the photovoltaic output characteristicsConstant current region (Constant Current Region, CCR). In this region, the conductance increase (dI/dV) of the photovoltaic output characteristic is approximately equal to zero, i.e. the output current of this region can ideally be constant.
FIG. 2 (a) shows the string current I of the photovoltaic group pv With respect to voltage V pv Is a changing relationship of (a). The CCR marked area is a constant current area, and three sections of constant current areas exist because of three different illuminations. Then, 3 characteristic voltage points V can be obtained by the calculation of the formula (1) init,1 ,V init,2 And V init,3 Is a value of (2). At the corresponding time, the reference voltage is set to a characteristic voltage value (V ref,1 ＝V init,1 ,V ref,2 ＝V init,2 ,V ref,3 ＝V init,3 ). In addition, the points marked by the pentagram are local power maximum peak points.
FIG. 2 (b) shows the photovoltaic current with respect to the voltage change rate dI/dV with respect to V pv Is a change curve of (a).
Step 3: determining a global maximum power point of the photovoltaic string according to the power data set; determining the photovoltaic module area where the photovoltaic module area is located according to the maximum power point; and then, tracking the maximum power point in real time in the photovoltaic module area.
Maximum power point maps characteristic voltage point V in output characteristic value init,max The specific calculation formula is as follows:
wherein n represents a characteristic voltage point V init Is a number of (3).
Tracking the maximum power point in real time in the photovoltaic module area specifically comprises the following steps:
wherein V is pv,ref (t) is the reference voltage corresponding to the photovoltaic working point of the current disturbance interval, V pv,ref (t-1) is the reference voltage corresponding to the photovoltaic working point of the previous disturbance interval,dV pv the characteristic voltage point V extracted for the current extraction time and the last extraction time init Is the difference of dP pv Initial power P extracted for current extraction time and last extraction time init Difference of V step Is the voltage step length; sign (x) is a sign function.
In one example, when x >0, sign (x) =1; when x=0, sign (x) =0; when x <0, sign (x) = -1.
Please refer to fig. 3, wherein P pv 、I pv And V pv The power, the current and the voltage are respectively output by the photovoltaic string. Detecting photovoltaic string output current I pv (t) and voltage V pv (t) (obtaining an output characteristic value of the photovoltaic string). Judging whether illumination changes, if so, updating V according to the formula (1) pv,ref Performing initial information acquisition (extracting characteristic voltage point V in constant current region) init ) The method comprises the steps of carrying out a first treatment on the surface of the If not, judging whether the initialization is completed, if so, judging whether the initialization is a GMPP area (determining a global maximum power point of the photovoltaic group string according to a power data set, and determining a photovoltaic module area where the photovoltaic group string is positioned according to the maximum power point); if not, then update V according to equation (2) pv,ref Is V (V) init，max Realizing rapid approach to GMPP; if yes, update V according to equation (3) pv,ref GMPP searching (tracking the maximum power point in real time in the photovoltaic module area) is implemented.
Please refer to fig. 4, wherein P pv 、I pv 、V pv The initial power, the characteristic current point and the characteristic voltage point which are output by the photovoltaic string are respectively.
Fig. 4 is a schematic working waveform diagram of the present method. At time t=0s, after extracting the characteristic voltage points (three corresponding to three photovoltaic panels), at the end of the fourth period (i.e. t=0.4 s, i.e. the fourth disturbance period, the disturbance period T p =0.1 s) reaches the vicinity of GMPP, and then starts in the fifth cycle (t=0.5 s) according to equation (3), perturbs around the GMPP point and achieves tracking of GMPP.
Please refer to fig. 5, wherein P pv 、I pv 、V pv The initial power, the characteristic current point and the characteristic voltage point which are output by the photovoltaic string are respectively.
Referring to fig. 5, in the Case of varying shadow masking, there are four different masking cases (Case I, case II, case III, case IV, respectively), when the masking cases are switched, the burst power suddenly changes, and thus a change in the masking Case is detected. The tracking method of the embodiments of the present invention is then restarted to find the new GMPP and track it. It can be seen that the embodiment of the invention can immediately respond and accurately and quickly find the GMPP under the condition of switching different shielding conditions.
Please refer to fig. 6, wherein fig. 6 (a), fig. 6 (b), and fig. 6 (c) are respectively related art GMPPT methods, and fig. 6 (d) is a method according to an embodiment of the present invention. P, P pv 、I pv 、V pv The initial power, the characteristic current point and the characteristic voltage point which are output by the photovoltaic string are respectively. Through comparison, the tracking speed of the global maximum power point is obviously higher than that of other schemes, and the method is advanced.
In summary, in the embodiment of the present invention, the output characteristic value of the photovoltaic string is obtained; the output characteristic value includes: current-voltage value and power-voltage value; the photovoltaic power generation system can be rapidly applied to the existing photovoltaic power generation system without adding an additional illumination sensor, and has higher cost efficiency. The feature area is divided only according to the information in the photovoltaic module data manual, so that the cost brought by system modeling is not required to be additionally increased, and efficient loading is realized.
Extracting characteristic voltage point V in output characteristic value init And according to the current value and the characteristic voltage point V in the output characteristic value init Calculating to obtain multiple initial powers P init The method comprises the steps of carrying out a first treatment on the surface of the Multiple initial powers P init Constructing a power data set; only the characteristic point extraction program is inserted into the existing maximum power point tracking controller, hardware or larger software modification is not needed, and the cost is effectively reduced.
Determining a global maximum power point of the photovoltaic string according to the power data set; and determining the photovoltaic group area where the photovoltaic group string is positioned according to the maximum power point, so as to judge the area where the global maximum power point of the photovoltaic group string is positioned under the condition of partial shadow shielding. The working point position of the photovoltaic string can be quickly switched to the region where the global maximum power point is located, and the maximum power point tracking is performed, so that the convergence speed of the global maximum power point is ensured, and the maximization of the output of the photovoltaic string is realized.
In order to achieve the above purpose, the embodiment of the present invention further provides the following solutions:
referring to fig. 7, the system for tracking global maximum power point of a photovoltaic string based on region segmentation includes:
the data acquisition module 1 is used for acquiring an output characteristic value of the photovoltaic string; the output characteristic value includes: current-voltage value and power-voltage value;
the characteristic voltage point extraction module 2 is connected with the data acquisition module 1, and the characteristic voltage point extraction module 4 is used for extracting a characteristic voltage point V in the output characteristic value init And according to the current value of the output characteristic value and the characteristic voltage point V init Calculating to obtain multiple initial powers P init The method comprises the steps of carrying out a first treatment on the surface of the Multiple initial powers P init Constructing a power data set;
the characteristic voltage point extraction module 2 includes:
the calculation unit is used for calculating the nth characteristic voltage point V initn The method comprises the steps of carrying out a first treatment on the surface of the The calculation formula is specifically as follows:
V init,n ＝[σ ccr +σ eq (n-1)]·V oc0 -(N m -n)·V bp ； (1)
wherein sigma ccr For coefficients operating in constant current region, sigma eq Is the equivalent working voltage of the photovoltaic module, V oc0 The open circuit voltage of the photovoltaic module under the standard test condition is 25 ℃ environment temperature, 1000W/m 2 The illumination intensity, the atmospheric mass AM 1.5; v (V) bp The turn-on voltage of the bypass diode of the photovoltaic module; n (N) m The individual photovoltaic modules form a photovoltaic string.
The determination module 3 includes:
the mapping unit is used for mapping the characteristic voltage point V of the output characteristic value of the maximum power point init,max The specific calculation formula is as follows:
wherein n represents a characteristic voltage point V init Is a number of (3).
The determining module 3 is connected with the characteristic voltage point extracting module 2, and the determining module 3 is used for:
determining a global maximum power point of the photovoltaic string according to the power data set; and determining the photovoltaic module area where the photovoltaic module area is located according to the maximum power point.
The tracking module 4 is connected with the determining module 3, and the tracking module 4 is used for tracking the maximum power point in real time in the photovoltaic module area.
The tracking module 4 includes:
the maximum power point tracking unit is used for tracking the maximum power point in real time in the photovoltaic module area, and specifically comprises the following steps:
wherein V is pv,ref (t) is the reference voltage corresponding to the photovoltaic working point of the current disturbance interval, V pv,ref (t-1) is the reference voltage corresponding to the photovoltaic working point of the last disturbance interval, dV pv The characteristic voltage point V extracted for the current extraction time and the last extraction time init Is the difference of dP pv Initial power P extracted for current extraction time and last extraction time init Difference of V step Is the voltage step length; sign (x) is a sign function.
Referring to fig. 8, a power conversion link of a photovoltaic string to a power grid is shown: the direct current power PV (PV Strings) emitted by the photovoltaic string is boosted to a direct current bus (DC-Link) by a DC-DC converter and then is merged into an alternating current Grid AC Grid by the DC-AC converter.
For the DC-AC link, the voltage and current of the output end and the DC-link reference voltage are sampled at first, and then the switching tube is driven by the Grid-side Control of the Grid-connected controller. L (L) inv ,L grid ,C f Is an inverterThe component parts of the LCL-filter, the DC/AC converter outputs filter parameters; v (V) g ,I g Voltage and current of the power grid; z is Z grid Is the equivalent impedance of the power grid.
For the DC-DC link, sampling the voltage and current of the photovoltaic string, and inputting the voltage and current into the GMPPT controller; then, photovoltaic reference voltage V pv,ref Given by the GMPPT controller. The voltage ring then stabilizes the voltage of the photovoltaic string according to the reference voltage. V (V) dc ,V dc,ref Respectively direct-current side voltage and reference voltage thereof; i pv ，V pv Current and voltage for the string of photovoltaic groups; v (V) pv,ref Is a photovoltaic string voltage reference; c (C) pv L is the input capacitance and inductance of the DC/DC converter DC-Link; PI (Proportional-Integral) is a Proportional-Integral controller. PWM (pulse Width modulation) b The duty ratio obtained by the PI compensator in the photovoltaic side controller (PV side control) further modulates the PWM wave generated.
In the present specification, each embodiment is described in a progressive manner, and each embodiment is mainly described in a different point from other embodiments, and identical and similar parts between the embodiments are all enough to refer to each other. For the system disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant points refer to the description of the method section.
The principles and implementations of the embodiments of the present invention have been described herein with reference to specific examples, the description of the above examples being only for the purpose of aiding in the understanding of the methods of the embodiments of the present invention and the core ideas thereof; also, it is within the spirit of the embodiments of the present invention for those skilled in the art to vary from one implementation to another and from application to another. In view of the foregoing, this description should not be construed as limiting the embodiments of the invention.
Claims (8)
1. The method for tracking the global maximum power point of the photovoltaic string based on the region segmentation is characterized by comprising the following steps of:
obtaining an output characteristic value of a photovoltaic string; the output characteristic value includes: current-voltage value and power-voltage value;
extracting a characteristic voltage point V in the output characteristic value init And according to the current value in the output characteristic value and the characteristic voltage point V init Calculating to obtain multiple initial powers P init The method comprises the steps of carrying out a first treatment on the surface of the The plurality of initial powers P init Constructing a power data set;
determining a global maximum power point of the photovoltaic group string according to the power data set; determining the photovoltaic module area where the maximum power point is located according to the maximum power point; and then tracking the maximum power point in real time in the photovoltaic module area.
2. The method for tracking global maximum power point of a photovoltaic string based on region segmentation according to claim 1, wherein the characteristic voltage point V in the output characteristic value is extracted init The method specifically comprises the following steps:
nth characteristic voltage point V init,n The calculation formula of (a) is specifically as follows:
V init,n ＝[σ ccr +σ eq (n-1)]·V oc0 -(N m -n)·V bp ；
wherein sigma ccr For the coefficient, sigma, of the constant current region operation eq Is the equivalent working voltage of the photovoltaic module, V oc0 Is open circuit voltage of the photovoltaic module under standard test conditions, wherein the standard test conditions are 25 ℃ environment temperature and 1000W/m 2 The illumination intensity, the atmospheric mass AM 1.5; v (V) bp The turn-on voltage of the bypass diode of the photovoltaic module; n (N) m The individual photovoltaic modules form a photovoltaic string.
3. The method for tracking global maximum power point of a photovoltaic string based on region segmentation according to claim 1, wherein the maximum power point maps a characteristic voltage point V in the output characteristic value init,max The specific calculation formula is as follows:
wherein the method comprises the steps ofN represents a characteristic voltage point V init Is a number of (3).
4. The method for tracking the global maximum power point of the photovoltaic string based on the region segmentation according to claim 1, wherein the method for tracking the maximum power point in real time in the photovoltaic module region specifically comprises the following steps:
wherein V is pv,ref (t) is the reference voltage corresponding to the photovoltaic working point of the current disturbance interval, V pv,ref (t-1) is the reference voltage corresponding to the photovoltaic working point of the last disturbance interval, dV pv The characteristic voltage point V extracted for the current extraction time and the last extraction time init Is the difference of dP pv Initial power P extracted for current extraction time and last extraction time init Difference of V step Is the voltage step length; sign (x) is a sign function.
5. A photovoltaic string global maximum power point tracking system based on region segmentation, comprising:
the data acquisition module is used for acquiring the output characteristic value of the photovoltaic string; the output characteristic value includes: current-voltage value and power-voltage value;
the characteristic voltage point extraction module is connected with the data acquisition module and is used for extracting a characteristic voltage point V in the output characteristic value init And according to the current value in the output characteristic value and the characteristic voltage point V init Calculating to obtain multiple initial powers P init The method comprises the steps of carrying out a first treatment on the surface of the The plurality of initial powers P init Constructing a power data set;
the determining module is connected with the characteristic voltage point extracting module and is used for:
determining a global maximum power point of the photovoltaic group string according to the power data set; determining the photovoltaic module area where the maximum power point is located according to the maximum power point;
and the tracking module is connected with the determining module and used for tracking the maximum power point in real time in the photovoltaic module area.
6. The regional division-based photovoltaic string global maximum power point tracking system of claim 5, wherein the characteristic voltage point extraction module comprises:
a calculation unit for calculating an nth characteristic voltage point V init,n The method comprises the steps of carrying out a first treatment on the surface of the The calculation formula is specifically as follows:
V init,n ＝[σ ccr +σ eq (n-1)]·V oc0 -(N m -n)·V bp ；
wherein sigma ccr For the coefficient, sigma, of the constant current region operation eq Is the equivalent working voltage of the photovoltaic module, V oc0 Is open circuit voltage of the photovoltaic module under standard test conditions, wherein the standard test conditions are 25 ℃ environment temperature and 1000W/m 2 The illumination intensity, the atmospheric mass AM 1.5; v (V) bp The turn-on voltage of the bypass diode of the photovoltaic module; n (N) m The individual photovoltaic modules form a photovoltaic string.
7. The zone division based photovoltaic string global maximum power point tracking system of claim 5, wherein the determining module comprises:
a mapping unit for mapping the characteristic voltage point V in the output characteristic value with the maximum power point init,max The specific calculation formula is as follows:
wherein n represents a characteristic voltage point V init Is a number of (3).
8. The zone division based photovoltaic string global maximum power point tracking system of claim 5, wherein the tracking module comprises:
the maximum power point tracking unit is configured to track a maximum power point in real time in the photovoltaic module area, and specifically includes:
wherein V is pv,ref (t) is the reference voltage corresponding to the photovoltaic working point of the current disturbance interval, V pv,ref (t-1) is the reference voltage corresponding to the photovoltaic working point of the last disturbance interval, dV pv The characteristic voltage point V extracted for the current extraction time and the last extraction time init Is the difference of dP pv Initial power P extracted for current extraction time and last extraction time init Difference of V step Is the voltage step length; sign (x) is a sign function.
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