CN116736929A - Photovoltaic string global maximum power point tracking method and system based on regional segmentation - Google Patents

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

Photovoltaic string global maximum power point tracking method and system based on regional segmentation

Technical field

The present invention relates to the technical field of photovoltaic power generation, and in particular to a method and system for tracking the global maximum power point of photovoltaic strings based on regional segmentation.

Background technique

Due to the instability of the external environment, photovoltaic power generation systems, especially distributed photovoltaic power generation systems, are extremely susceptible to cloud movement, building shading, etc., and photovoltaic strings are partially shaded, resulting in photovoltaic string output characteristic curves. Presenting a multi-peaked state. In order to ensure the maximum output of photovoltaic strings, Global Maximum Power Point Tracking (GMPPT) is widely used in photovoltaic power generation systems to maximize photovoltaic output energy and thereby improve the overall efficiency of the system.

The traditional GMPPT algorithm based on global scanning needs to search most areas of the photovoltaic curve, which introduces redundant search points and reduces the convergence speed of the algorithm. The GMPPT solution based on intelligent algorithms requires optimization of preset parameters or a large amount of training data to achieve fast tracking, but it will bring a greater computational burden to the system. The traditional model-based GMPPT solution requires accurate modeling of the photovoltaic strings, has higher requirements for mathematical calculations, and may introduce light sensors and increase system costs.

Contents of the invention

The purpose of the embodiments of the present invention is to provide a method and system for tracking the global maximum power point of photovoltaic strings based on regional segmentation, to improve the search efficiency for reaching the global maximum power point, and to maximize the output when the photovoltaic string is partially shaded.

To achieve the above objectives, embodiments of the present invention provide the following solutions:

A global maximum power point tracking method for photovoltaic strings based on regional segmentation, including:

Obtain the output characteristic value of the photovoltaic string; the output characteristic value includes: current-voltage value and power-voltage value;

Extract the characteristic voltage point V _init in the output characteristic value, and calculate multiple initial powers P _init according to the current value in the output characteristic value and the characteristic voltage point V _init ; the multiple initial powers P _init form a power data set;

Determine the global maximum power point of the photovoltaic string according to the power data set; and determine the photovoltaic module area where it is located based on the maximum power point; and then track the maximum power point in the photovoltaic module area in real time.

Optionally, extracting the characteristic voltage point V _init in the output characteristic value specifically includes:

The calculation formula of the nth characteristic voltage point V _init,n is specifically:

V _init,n =[σ _ccr +σ _eq (n-1)]·V _oc0 -(N _m -n)·V _bp ;

Among them, σ _ccr is the coefficient of operation in the constant current zone, σ _eq is the equivalent operating voltage of the photovoltaic module, V _oc0 is the open circuit voltage of the photovoltaic module under standard test conditions, and the standard test conditions are 25°C ambient temperature, 1000W/m ² light intensity, air quality AM 1.5; V _bp is the conduction voltage of the bypass diode of the photovoltaic module; N _m photovoltaic modules constitute a photovoltaic string.

Optionally, the maximum power point maps the characteristic voltage point V _init,max in the output characteristic value. The specific calculation formula is:

Among them, n represents the number of characteristic voltage points V _init .

Optionally, track the maximum power point in the photovoltaic module area in real time, specifically including:

Among them, V _pv,ref (t) is the reference voltage corresponding to the photovoltaic operating point of the current disturbance interval, V _pv,ref (t-1) is the reference voltage corresponding to the photovoltaic operating point of the previous disturbance interval, dV _pv is the current extraction time and The difference between the characteristic voltage point V _init extracted at the last extraction time, dP _pv is the difference between the current extraction time and the initial power P _init extracted at the previous extraction time, V _step is the voltage step size; sign(x) is symbolic function.

In order to achieve the above objects, embodiments of the present invention also provide the following solutions:

A global maximum power point tracking system for photovoltaic strings based on regional division, including:

A data acquisition module is used to obtain the output characteristic values of the photovoltaic string; the output characteristic values include: current-voltage value and power-voltage value;

A characteristic voltage point extraction module, connected to the data acquisition module, is used to extract the characteristic voltage point V _init in the output characteristic value, and calculate it according to the current value in the output characteristic value and the characteristic voltage point V _init Multiple initial powers P _init are obtained; the multiple initial powers P _init constitute a power data set;

Determination module, connected with the characteristic voltage point extraction module, used for:

Determine the global maximum power point of the photovoltaic string according to the power data set; and determine the photovoltaic module area where it is located according to the maximum power point;

A tracking module, connected to the determination module, is used to track the maximum power point in the photovoltaic module area in real time.

Optionally, the characteristic voltage point extraction module includes:

Calculation unit, used to calculate the nth characteristic voltage point V _init,n ; the calculation formula is specifically:

V _init,n =[σ _ccr +σ _eq (n-1)]·V _oc0 -(N _m -n)·V _bp ;

Among them, σ _ccr is the coefficient of operation in the constant current zone, σ _eq is the equivalent operating voltage of the photovoltaic module, V _oc0 is the open circuit voltage of the photovoltaic module under standard test conditions, and the standard test conditions are 25°C ambient temperature, 1000W/m ² light intensity, air quality AM 1.5; V _bp is the conduction voltage of the bypass diode of the photovoltaic module; N _m photovoltaic modules constitute a photovoltaic string.

Optionally, the determining module includes:

The mapping unit is used for maximum power point mapping of the characteristic voltage point V _init,max in the output characteristic value. The specific calculation formula is:

Among them, n represents the number of characteristic voltage points V _init .

Optionally, the tracking module includes:

Maximum power point tracking unit, used to track the maximum power point in the photovoltaic module area in real time, specifically including:

Among them, V _pv,ref (t) is the reference voltage corresponding to the photovoltaic operating point of the current disturbance interval, V _pv,ref (t-1) is the reference voltage corresponding to the photovoltaic operating point of the previous disturbance interval, dV _pv is the current extraction time and The difference between the characteristic voltage point V _init extracted at the last extraction time, dP _pv is the difference between the current extraction time and the initial power P _init extracted at the previous extraction time, V _step is the voltage step size; sign(x) is symbolic function.

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; there is no need to add additional light sensors and can be quickly applied to existing photovoltaic power generation systems. , with high cost-effectiveness. The division of characteristic areas only needs to be done based on the information in the photovoltaic module data sheet, without the additional cost of system modeling to achieve efficient loading.

Extract the characteristic voltage point V _init in the output characteristic value, and calculate multiple initial powers P _init based on the current value and characteristic voltage point V _init in the output characteristic value; multiple initial powers P _init constitute a power data set; just The feature point extraction program is inserted into the existing maximum power point tracking controller without the need for hardware or major software modifications, effectively reducing costs.

Determine the global maximum power point of the photovoltaic string based on the power data set; and determine the photovoltaic group area where it is located based on the maximum power point, realizing the determination of the area where the global maximum power point of the photovoltaic string is located under partial shadowing. It can quickly switch the working point of the photovoltaic string to the area where the global maximum power point is located and perform maximum power point tracking, ensuring the convergence speed to the global maximum power point and maximizing the output of the photovoltaic string.

Description of drawings

In order to explain the embodiments of the present invention or the technical solutions in the prior art more clearly, the drawings needed to be used in the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some of the drawings of the present invention. Embodiments, for those of ordinary skill in the art, other drawings can also be obtained based on these drawings without exerting creative efforts.

Figure 1 is a schematic flow chart of a photovoltaic string global maximum power point tracking method based on regional segmentation provided by an embodiment of the present invention;

Figure 2 is a schematic diagram of constant current area and characteristic point voltage extraction provided by the embodiment of the present invention; Figure 2(a) is a schematic diagram of the relationship between the photovoltaic string current I _pv and voltage V _pv ; Figure 2(b) is a voltage change Schematic diagram of the change curves of rates dI/dV and V _pv ;

Figure 3 is a control block diagram of a photovoltaic string global maximum power point tracking method based on regional segmentation provided by an embodiment of the present invention;

Figure 4 is a schematic diagram of the operation results of the photovoltaic string global maximum power point tracking method based on regional segmentation under static partial shadowing provided by the embodiment of the present invention; Figure 4(a) is a photovoltaic power P _pv operating waveform diagram; Figure 4(b) is the working waveform diagram of photovoltaic voltage V _pv ; Figure 4(c) is the working waveform diagram of photovoltaic current I _pv ;

Figure 5 is a schematic diagram of the operation results of the photovoltaic string global maximum power point tracking method based on regional segmentation in the case of dynamic partial shadowing provided by the embodiment of the present invention;

Figure 6 is a comparison diagram between the photovoltaic string global maximum power point tracking method based on regional segmentation and the existing technology in the case of static partial shadow shading according to the embodiment of the present invention;

Figure 7 is a schematic structural diagram of a photovoltaic string global maximum power point tracking system based on regional segmentation provided by an embodiment of the present invention;

FIG. 8 is an overall control structure diagram of a photovoltaic string global maximum power point tracking system based on area segmentation provided by an embodiment of the present invention.

Symbol Description:

Data acquisition module-1, characteristic voltage point extraction module-2, determination module-3, tracking module-4.

Detailed ways

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of the present invention.

The purpose of the present invention is to provide a method and system for tracking the global maximum power point of photovoltaic strings based on regional segmentation, so as to solve the existing problem of low search efficiency of the global maximum power point.

In order to make the above objects, features and advantages of the present invention more obvious and understandable, the present invention will be described in further detail below with reference to the accompanying drawings and specific embodiments.

Figure 1 shows an exemplary process of the above-mentioned regional segmentation-based global maximum power point tracking method for photovoltaic strings. Each step is introduced in detail below.

Step 1: Obtain the output characteristic values of the photovoltaic string; the output characteristic values include: current-voltage value and power-voltage value.

Step 2: Extract the characteristic voltage point V _init in the output characteristic value, and calculate multiple initial powers P _init based on the current value and the characteristic voltage point V _init in the output characteristic value; multiple initial powers P _init constitute a power data set; Specifically include:

The calculation formula of the nth characteristic voltage point V _init,n is specifically:

V _init,n =[σ _ccr +σ _eq (n-1)]·V _oc0 -(N _m -n)·V _bp ; (1)

Among them, σ _ccr is the coefficient of constant current zone operation, σ _eq is the equivalent operating voltage of the photovoltaic module, and V _oc0 is the open circuit voltage of the photovoltaic module under standard test conditions. The standard test conditions are 25°C ambient temperature, 1000W/ m ² light intensity, air quality AM 1.5; V _bp is the conduction voltage of the bypass diode of the photovoltaic module; N _m photovoltaic modules constitute a photovoltaic string.

In one example, extracting the characteristic voltage point V _init in the constant current region (Constant Current Region, CCR) can be specifically an initialization process. In the initialization process, the characteristic voltage points in n constant current regions are divided into output characteristic regions. V _init , (V _init ∈ [V _init,1 ,V _init,2 ,…,V _init,n ]) is searched to determine the constant current area where the global maximum power point (GMPP) of the photovoltaic string is located . In this initialization process, the characteristic voltage point Vinit is collected by adjusting the working point voltage of the photovoltaic string. The number of characteristic voltage points V _init of the photovoltaic string in the initialization process that needs to be collected corresponds to the number of photovoltaic modules in the string N _m be consistent.

Figure 2 shows the output characteristics of a photovoltaic string composed of three MSX-60 photovoltaic panels under a certain shadow shielding condition, where I _pv and V _pv are the output current and output voltage of the photovoltaic string respectively. The CCR region marked in Figure 2 is the Constant Current Region (CCR) in the photovoltaic output characteristic curve. In this region, the conductance increment (dI/dV) of the photovoltaic output characteristic curve is almost equal to zero, that is, the output current in this region can ideally be a constant value.

Figure 2(a) shows the relationship between the photovoltaic string current I _pv and the voltage V _pv . The CCR marked area is the constant current area. Since there are three different lighting conditions, there are three constant current areas. Next, the values of the three characteristic voltage points V _init,1 , V _init,2 and V _init,3 can be obtained through calculation using equation (1). At the corresponding time, the reference voltage is set to the characteristic voltage value (V _ref,1 =V _init,1 , V _ref,2 =V _init,2 , V _ref,3 =V _init,3 ). In addition, the point marked by the pentagram is the maximum local power peak point.

Figure 2(b) shows the change curve of the photovoltaic current with respect to the voltage change rate dI/dV with respect to V _pv .

Step 3: Determine the global maximum power point of the photovoltaic string based on the power data set; and determine the photovoltaic module area where it is located based on the maximum power point; then, track the maximum power point in the photovoltaic module area in real time.

The maximum power point maps the characteristic voltage point V _init,max in the output characteristic value. The specific calculation formula is:

Among them, n represents the number of characteristic voltage points V _init .

Track the maximum power point in real time in the photovoltaic module area, including:

Among them, V _pv,ref (t) is the reference voltage corresponding to the photovoltaic operating point of the current disturbance interval, V _pv,ref (t-1) is the reference voltage corresponding to the photovoltaic operating point of the previous disturbance interval, dV _pv is the current extraction time and The difference between the characteristic voltage point V _init extracted at the last extraction time, dP _pv is the difference between the current extraction time and the initial power P _init extracted at the previous extraction time, V _step is the voltage step size; sign(x) is symbolic 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 Figure 3, where P _pv , I _pv and V _pv are the power, current and voltage output by the photovoltaic string respectively. Detect the photovoltaic string output current I _pv (t) and voltage V _pv (t) (obtain the output characteristic value of the photovoltaic string). Determine whether the illumination changes. If so, update V _{pv, ref} according to formula (1) to collect initialization information (extract the characteristic voltage point V _init in the constant current area); if not, determine whether the initialization is completed. If so, determine whether is the GMPP area (determine the global maximum power point of the photovoltaic string based on the power data set; and determine the photovoltaic module area where it is located based on the maximum power point); if not, update V _{pv according to formula (2), ref} is V _{init, max} Achieve rapid approach to GMPP; if so, update V _{pv, ref} according to formula (3) to achieve GMPP search (real-time tracking of the maximum power point in the photovoltaic module area).

Please refer to Figure 4, where P _pv , I _pv , and V _pv are the initial power, characteristic current point, and characteristic voltage point output by the photovoltaic string respectively.

Figure 4 is a schematic working waveform diagram of this method. At t=0s, after extracting the characteristic voltage points (three in total, corresponding to three photovoltaic panels), it ends at the fourth period (that is, t=0.4s, which is the fourth disturbance period, and the disturbance period T _p =0.1s ) reaches near the GMPP, and then according to equation (3), starting from the fifth period (t=0.5s), it perturbs near the GMPP point and realizes tracking of the GMPP.

Please refer to Figure 5, where P _pv , I _pv , and V _pv are the initial power, characteristic current point, and characteristic voltage point output by the photovoltaic string respectively.

Please refer to Figure 5. Under the changing shadow shadowing situation, there are four different shadowing situations (CaseI, Case II, Case III, Case IV respectively). When the shadowing situation is switched, the string power changes suddenly. Changes in occlusion are thereby detected. Then, the tracking method of the embodiment of the present invention is restarted to find the new GMPP and track it. It can be seen that the embodiment of the present invention can respond immediately when switching between different shielding conditions, and find the GMPP accurately and quickly.

Please refer to Figure 6 , where Figure 6(a), Figure 6(b), and Figure 6(c) respectively show the GMPPT method in the prior art, and Figure 6(d) shows the method proposed in the embodiment of the present invention. , P _pv , I _pv , and V _pv are the initial power, characteristic current point, and characteristic voltage point output by the photovoltaic string respectively. Through comparison, it is found that the tracking speed of the global maximum power point of the present invention is significantly higher than that of other solutions, which reflects the advancement of this method.

To sum up, 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; there is no need to add additional light sensors and can be quickly applied to existing Among the photovoltaic power generation systems, it has high cost-effectiveness. The division of characteristic areas only needs to be done based on the information in the photovoltaic module data sheet, without the additional cost of system modeling to achieve efficient loading.

Extract the characteristic voltage point V _init in the output characteristic value, and calculate multiple initial powers P _init based on the current value and characteristic voltage point V _init in the output characteristic value; multiple initial powers P _init constitute a power data set; just The feature point extraction program is inserted into the existing maximum power point tracking controller without the need for hardware or major software modifications, effectively reducing costs.

Determine the global maximum power point of the photovoltaic string based on the power data set; and determine the photovoltaic group area where it is located based on the maximum power point, realizing the determination of the area where the global maximum power point of the photovoltaic string is located under partial shadowing. It can quickly switch the working point of the photovoltaic string to the area where the global maximum power point is located and perform maximum power point tracking, ensuring the convergence speed to the global maximum power point and maximizing the output of the photovoltaic string.

In order to achieve the above objects, embodiments of the present invention also provide the following solutions:

A global maximum power point tracking system for photovoltaic strings based on regional segmentation, see Figure 7, including:

The data acquisition module 1 is used to obtain the output characteristic values of the photovoltaic string; the output characteristic values include: current-voltage value and power-voltage value;

The characteristic voltage point extraction module 2 is connected to the data acquisition module 1. The characteristic voltage point extraction module 4 is used to extract the characteristic voltage point V _init in the output characteristic value, and calculate the polynomial based on the current value of the output characteristic value and the characteristic voltage point V _init An initial power P _init ; multiple initial powers P _init constitute a power data set;

Feature voltage point extraction module 2 includes:

The calculation unit is used to calculate the nth characteristic voltage point V _initn ; the calculation formula is specifically:

V _init,n =[σ _ccr +σ _eq (n-1)]·V _oc0 -(N _m -n)·V _bp ; (1)

Among them, σ _ccr is the coefficient of constant current zone operation, σ _eq is the equivalent operating voltage of the photovoltaic module, V _oc0 is the open circuit voltage of the photovoltaic module under standard test conditions, and the standard test conditions are 25°C ambient temperature, 1000W/m ² Light intensity, air quality AM 1.5; V _bp is the conduction voltage of the bypass diode of the photovoltaic module; N _m photovoltaic modules constitute a photovoltaic string.

Determine module 3 includes:

The mapping unit is used to map the characteristic voltage point V _init,max of the maximum power point output characteristic value. The specific calculation formula is:

Among them, n represents the number of characteristic voltage points V _init .

The determination module 3 is connected to the characteristic voltage point extraction module 2, and the determination module 3 is used for:

Determine the global maximum power point of the photovoltaic string based on the power data set; and determine the photovoltaic module area where it is located based on the maximum power point.

The tracking module 4 is connected to the determination module 3, and the tracking module 4 is used to track the maximum power point in the photovoltaic module area in real time.

Tracking module 4 includes:

The maximum power point tracking unit is used to track the maximum power point in real time in the photovoltaic module area, including:

Among them, V _pv,ref (t) is the reference voltage corresponding to the photovoltaic operating point of the current disturbance interval, V _pv,ref (t-1) is the reference voltage corresponding to the photovoltaic operating point of the previous disturbance interval, dV _pv is the current extraction time and The difference between the characteristic voltage point V _init extracted at the last extraction time, dP _pv is the difference between the current extraction time and the initial power P _init extracted at the previous extraction time, V _step is the voltage step size; sign(x) is symbolic function.

Please refer to Figure 8, which shows the power conversion link from the photovoltaic string to the power grid: the DC power PV (PV Strings) emitted by the photovoltaic string is boosted to the DC bus (DC-Link) by the DC-DC converter, and then It is integrated into the AC grid by the DC-AC converter.

Among them, for the DC-AC link, the voltage, current and DC-link reference voltage at the output end are first sampled, and then the switching tube is driven by the grid-side controller to achieve this. L _inv , L _grid , C _f are the components of the inverter LCL-filter, and the DC/AC converter output filter parameters; V _g , I _g are the voltage and current of the grid; Z _grid is the equivalent impedance of the grid.

For the DC-DC link, the voltage and current of the photovoltaic string are sampled and input into the GMPPT controller; then, the photovoltaic reference voltage V _pv,ref is given by the GMPPT controller. The voltage loop then stabilizes the voltage of the PV string based on the reference voltage. V _dc , V _{dc, ref} are the DC side voltage and its reference voltage respectively; I _pv , V _pv are the current and voltage of the photovoltaic string; V _{pv, ref} are the photovoltaic string voltage reference; C _pv , L is DC/DC The input capacitance and inductance of the converter DC-Link; PI (Proportional-Integral) is a proportional-integral controller. PWM _b is the duty cycle obtained by the PI compensator in the photovoltaic side controller (PV side control), and then modulates the generated PWM wave.

Each embodiment in this specification is described in a progressive manner. Each embodiment focuses on its differences from other embodiments. The same and similar parts between the various embodiments can be referred to each other. As for the system disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple. For relevant details, please refer to the description in the method section.

This article uses specific examples to illustrate the principles and implementation methods of the embodiments of the present invention. The description of the above embodiments is only used to help understand the methods and core ideas of the embodiments of the present invention; at the same time, for those of ordinary skill in the art According to the ideas of the embodiments of the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this description should not be understood as limiting the embodiments of the present 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.