CN115549205A

CN115549205A - Method for positioning and optimizing series mismatch and parallel mismatch of components of photovoltaic power station

Info

Publication number: CN115549205A
Application number: CN202211230175.2A
Authority: CN
Inventors: 单峻; 孔超; 张旭光; 许杰; 杨睿; 张永
Original assignee: FONRICH NEW ENERGY TECHNOLOGY Ltd SHANGHAI; Huaneng Xuzhou Tongshan Wind Power Generation Co ltd; Clean Energy Branch of Huaneng International Power Jiangsu Energy Development Co Ltd Clean Energy Branch
Current assignee: FONRICH NEW ENERGY TECHNOLOGY Ltd SHANGHAI; Huaneng Xuzhou Tongshan Wind Power Generation Co ltd; Clean Energy Branch of Huaneng International Power Jiangsu Energy Development Co Ltd Clean Energy Branch
Priority date: 2022-10-08
Filing date: 2022-10-08
Publication date: 2022-12-30

Abstract

The invention mainly relates to a method for positioning and optimizing series mismatch and parallel mismatch of components of a photovoltaic power station. The photovoltaic modules working on the left side of the maximum power point are classified and connected in series into a first type battery string, and the photovoltaic modules working on the right side of the maximum power point are classified and connected in series into a second type battery string, so that power mismatch between the photovoltaic modules with different maximum power point distributions is avoided when the first type battery string and the second type battery string are connected in series and parallel.

Description

Method for positioning and optimizing series mismatch and parallel mismatch of components of photovoltaic power station

Technical Field

The invention mainly relates to the field of photovoltaic power generation, in particular to a method for positioning and optimizing series mismatch and parallel mismatch of components of a photovoltaic power station in a photovoltaic power generation system containing photovoltaic components.

Background

The photovoltaic module is used as an important core component of the photovoltaic power generation system, the excellent performance of the photovoltaic module directly influences the overall effect of the power generation system, in fact, the photovoltaic module is subjected to more restriction factors, and the characteristic difference of each photovoltaic module can cause the loss of the connection combination efficiency. The photovoltaic device array is generally in series-parallel connection, and if one of the cell devices is subjected to power reduction caused by shadow or dust, or shading or aging, other devices in series-parallel connection may be affected by the reduction of voltage and current intensity. In order to guarantee the safety and reliability of the operation of the photovoltaic array, it is important to fully exert the maximum power generation efficiency of each photovoltaic module and guarantee that the photovoltaic modules are in a normal working state.

The inefficiency of solar power generation is largely due to the concealment of the mismatch of the photovoltaic modules, and the owner or user may ignore or not know the mismatch problem of the photovoltaic modules, resulting in reduced return on investment and profit, and causing energy waste to some extent. The mechanism of mismatch is multifaceted, with the main factors generally being the combined mismatch of cell voltage and cell current, which is provoked by contamination shadowing and flying clouds, building shading, surface contamination, different installation tilt angles and sunlight installation orientations, aging, ambient temperature, mismatch between components, etc. The mismatch of the photovoltaic modules results in unbalanced power loss of the photovoltaic modules, and the whole power generation system cannot operate at the optimal output power point.

The photovoltaic inverter is a core junction device in the photovoltaic power generation system, and the photovoltaic inverter can realize the conversion from direct current to alternating current by controlling the switch device. The operation condition of the photovoltaic inverter has important influence on the reliable operation and the power generation efficiency of the whole photovoltaic power generation system. However, the natural environment of the photovoltaic power plant is generally harsh, and the internal devices are subjected to high electrical stress and high thermal stress for a long time. Meanwhile, the negative effects of grid and dc side disturbances can also inadvertently increase the mismatch incidence of the pv inverter, resulting in loss of efficiency. In addition, some pv inverters may not be low in performance due to intrinsic factors of the pv system, such as mismatch between series and parallel of pv modules, so the actual operating efficiency and power generation efficiency of the pv inverters are always far from the rated efficiency and performance.

When the overall efficiency of a photovoltaic power generation system is counted, it is usually assumed that all the photovoltaic modules used have the same illumination radiance, temperature and performance parameters. However, in practical situations, the current and voltage mismatch and inefficiency of the module may be caused by the external factors such as partial shading effect, temperature imbalance and installation tilt angle. Shadow masking causes power loss in many forms, perhaps seasonal over the years or several hours of the day, which is not readily noticeable for short periods but causes long term power loss.

The power matching optimization scheme is integrated into the design of the photovoltaic power generation system in advance, so that the power generation efficiency of the photovoltaic power station can be improved, the service life of a battery can be prolonged, and the return on investment can be improved. However, it is still a difficult problem how to solve the matching degree between the photovoltaic modules and the matching degree between the battery strings so as to solve the module mismatch and optimize and improve the power generation.

Disclosure of Invention

The application relates to a method for positioning and optimizing series mismatch and parallel mismatch of components of a photovoltaic power station, which comprises the following steps:

the photovoltaic modules working on the left side of the maximum power point are classified and connected in series into a first-class battery string, and the photovoltaic modules working on the right side of the maximum power point are classified and connected in series into a second-class battery string, so that when the first-class battery string and the second-class battery string are connected in series and parallel, power mismatch among the photovoltaic modules with different maximum power point distributions is avoided.

The method described above, wherein: and classifying the photovoltaic modules which just work at the maximum power point position and connecting the photovoltaic modules in series to form a third type battery string, wherein the third type battery string is used for connecting the first type battery string and the second type battery string in parallel.

The method described above, wherein: the inverter is powered by at least the first type battery pack string and the second type battery pack string, the maximum power point of each photovoltaic module is dynamically analyzed in the process that the inverter executes maximum power tracking, and secondary optimization is executed:

classifying photovoltaic components working on the right side of the maximum power point in the first battery string into a second battery string;

and classifying the photovoltaic modules which work at the left side of the maximum power point in the second battery string into the first battery string.

The method described above, wherein: in the execution of the secondary optimization stage: photovoltaic modules which just work at the position of the maximum power point in the first type battery strings and the second type battery strings are classified into third type battery strings, and the first type battery strings are connected with the third type battery strings in parallel.

The method described above, wherein: the sign of the property that the variation of the output power of the photovoltaic module is greater than the variation of the output voltage of the upper photovoltaic module determines whether the photovoltaic module operates on the left side or the right side of the maximum power point: if the property symbol is a positive sign, the photovoltaic module works on the left side of the maximum power point; if the property sign is negative, the photovoltaic module operates on the right side of the maximum power point.

The method described above, wherein: and if the variable quantity of the output power of the photovoltaic component is closer to zero than the variable quantity of the output voltage of the upper photovoltaic component, the photovoltaic component just works at the maximum power point position.

The method described above, wherein: the device for connecting photovoltaic modules in series comprises: one of a photovoltaic junction box that connects the photovoltaic module into the battery string, a shut-off device that removes the photovoltaic module from the battery string or restores the photovoltaic module in a removed state into the battery string, a power optimizer that sets the photovoltaic module at its maximum power point, and a voltage converter that performs voltage conversion on an initial voltage of the photovoltaic module.

The method described above, wherein: the equipment is also provided with a data acquisition module for acquiring the output power and the output voltage of the photovoltaic module and analyzing the variable quantity of the output power and the variable quantity of the output voltage of the photovoltaic module.

In addition to the foregoing embodiments, the present application also discloses another method for positioning and optimizing series and parallel mismatch of components of a photovoltaic power plant, comprising: analyzing the property sign of the variable quantity of the output power of the photovoltaic assembly to the variable quantity of the output voltage of the upper photovoltaic assembly; connecting photovoltaic modules with positive signs in series to form a battery pack string of one category; connecting photovoltaic modules with negative signs in series to form battery strings in another category; in order to avoid power mismatch between photovoltaic modules with different maximum power point distributions when different types of strings are connected in parallel with each other.

The method described above, wherein: the inverter is powered by at least battery pack strings of different types, the maximum power point of each photovoltaic module is dynamically analyzed in the process that the inverter executes maximum power tracking, and secondary optimization is executed:

and in each battery string in different categories, photovoltaic modules with the property symbols changed into positive signs are classified into battery string categories which are connected in series with each other, and photovoltaic modules with the property symbols changed into negative signs are classified into battery string categories which are connected in series with each other.

In addition to the foregoing embodiments, the present application is directed to a method of addressing component mismatches and optimizing power generation in a photovoltaic power plant and such method of optimizing power generation includes: the foregoing description relates to the location and optimization of series and parallel mismatch of components of a photovoltaic power plant. The problem that the photovoltaic power generation efficiency is low due to intrinsic factors such as software and hardware design (usually in the aspect of power integration) and the like in the photovoltaic system is solved, series-parallel mismatch and the like of photovoltaic modules are optimized, and the actual operation efficiency and the power generation efficiency of the power system with the photovoltaic inverter reach the optimal performance.

Drawings

To make the above objects, features and advantages more comprehensible, embodiments accompanied with figures are described in detail below, and features and advantages of the present application will become apparent upon reading the following detailed description and upon reference to the following figures.

Fig. 1 shows photovoltaic modules supplying bus lines in series and possible series-parallel mismatch between modules.

Fig. 2 is a graph of the power mismatch between photovoltaic modules with different maximum power point distributions after adjustment.

Fig. 3 shows that parameters such as output power and output voltage of each photovoltaic module in the string are sent to an analyzer.

Figure 4 is a photovoltaic module configured with a voltage converter to raise or lower the voltage of the photovoltaic module.

Fig. 5 shows the connection of a photovoltaic module to a bus bar by means of a photovoltaic junction box equipped with a data acquisition module.

Fig. 6 shows the connection of the photovoltaic module to the bus bar by means of a shut-off device equipped with a data acquisition module.

Fig. 7 shows the connection of a photovoltaic module to a bus bar by means of a voltage converter equipped with a data acquisition module.

Fig. 8 is a photovoltaic module which operates on the left side and the right side of the maximum power point and is classified and then connected in series and in parallel.

Detailed Description

The present invention will be described more fully hereinafter with reference to the accompanying drawings, in which some, but not all embodiments of the invention are shown and described, and which, based on the foregoing, are given by way of illustration only, and which, without any inventive step, are within the scope of the invention.

Referring to fig. 1, in an alternative example, illustrated by battery strings ST1-STM, M is a positive integer exceeding 1 and a number of tens or more of strings connected in parallel is often used for a single inverter of a photovoltaic plant. The limited number of strings in the figures is merely an illustrative example and is not meant to be a specific limitation.

Referring to fig. 1, power is supplied to bus bars B1-B2 by respective parallel battery strings ST 1-STM. An energy management device 100 such as an inverter, a combiner box, or a charger receives electric energy supplied from each battery string from a bus.

Referring to fig. 4, the power generation system includes a plurality of photovoltaic modules P1-PN and includes a plurality of voltage converters DC/DC (e.g., local devices J1-JN are voltage converters) connected in series, each of the voltage converters (e.g., JN) converting the electric energy received from a corresponding one of the photovoltaic modules PN into its own output power. The respective output voltages of the multilevel voltage converters are superimposed on the dc bus B1-B2 and thereby serve as bus voltages. The inverter INVT performs power conversion on the output power supplied from the multi-stage voltage converter and generates alternating current.

Referring to fig. 5, the power generation system includes a plurality of photovoltaic modules P1-PN and the power generation system includes a plurality of photovoltaic junction boxes (e.g., local devices J1-JN are photovoltaic junction boxes) connected in series, each photovoltaic junction box (e.g., JN) is used for connecting a corresponding photovoltaic module PN to a battery string.

Referring to fig. 6, the power generation system includes a plurality of photovoltaic modules P1-PN, and further includes a plurality of series-connected shutdown devices (for example, the local devices J1-JN are fast shutdown devices), and each of the shutdown devices (for example, JN) is further configured to remove a corresponding one of the photovoltaic modules PN from the string of battery packs or to re-insert the photovoltaic module PN in a removed state into the string of battery packs.

Referring to fig. 7, the power generation system includes a plurality of photovoltaic modules P1-PN and the power generation system includes a plurality of power optimizers (e.g., power optimizers used by local devices J1-JN) connected in series, and each of the shutdown devices (e.g., JN) is further configured to set a corresponding one of the photovoltaic modules PN at its maximum power point.

Referring to fig. 1, the maximum photovoltaic module power depends on the optimal operating current multiplied by the optimal operating voltage: each photovoltaic module has a unique maximum power point that corresponds to the maximum power output of the photovoltaic module, which is approximately a function of an exponential relationship with respect to voltage and current. For example, refer to the power optimization apparatus disclosed in chinese patent application 201110097292.1, which is used to monitor and optimize the power of each photovoltaic panel, where any panel in the array has a mismatch problem, and other cells can still output maximum power to compensate the power generation loss caused by the mismatch problem. The method aims to integrate a power matching scheme into the design of a photovoltaic power generation system in advance, and solves the problem of assembly mismatch and the problem of battery string mismatch at the system integration level.

Referring to fig. 1, the existing method for evaluating the mismatch of the devices or strings has certain disadvantages, and in particular, the evaluation research of the efficiency loss in the case of series-parallel connection of photovoltaic devices involves less. Therefore, a mismatch solution compatible with the photovoltaic grid-connected inverter and the component in the case of series-parallel connection and the case of tracking the maximum power point needs to be established, so that the efficiency loss caused by series mismatch and parallel mismatch of the photovoltaic components in the photovoltaic system is effectively recovered, and optimized power generation is realized.

Referring to fig. 1, factors affecting the accuracy of the efficacy assessment also include the rationality of the assessment method. The existing evaluation method mostly takes a normally-operated photovoltaic power station as an evaluation object. The system energy efficiency PR value is taken as a globally recognized key efficiency index and has guiding significance for measuring the power generation performance of the whole photovoltaic system under the normal operation condition. However, the evaluation of the efficiency of the photovoltaic power station by the system energy efficiency usually takes the year and month as a time unit, and factors such as geographical positions, weather, illumination intensity and the like which affect the efficiency of the photovoltaic power station are selected as evaluation indexes, so that the evaluation is relatively more biased to the efficiency evaluation when the photovoltaic system normally operates, but is not suitable for the efficiency loss evaluation of devices in the photovoltaic system caused by the mismatch of photovoltaic modules.

With reference to fig. 1, in terms of the management of the components of the photovoltaic module: a plurality of photovoltaic modules P1-PN supply the bus in series and assuming that the bus comprises a positive bus B1 and a negative bus B2, the positive pole of one string of the series of photovoltaic modules P1-PN is coupled to the so-called positive bus B1, and correspondingly the negative pole of the aforesaid string of the series of photovoltaic modules P1-PN is coupled to the so-called negative bus B2. For example, each pv module is equipped with a pv junction box, which in a pv system mainly serves to connect the electrical energy generated by the pv module to external wiring and allows the pv junction box to have bypass diodes in some cases, so that when an abnormality occurs in the pv module, such as a hot spot effect, the abnormal pv module can be bypassed by the bypass diodes of the pv junction box.

Referring to fig. 1, in the field of photovoltaic power generation, a photovoltaic module, that is, a photovoltaic cell, is a core component of power generation, and a solar panel is divided into a monocrystalline silicon cell, a polycrystalline silicon solar cell, an amorphous silicon solar cell, and the like in a mainstream technical direction. The number of photovoltaic modules adopted by a large centralized photovoltaic power station is huge, while the number of photovoltaic modules adopted by a small household small power station in a small scale is relatively small. Silicon substrate photovoltaic modules require service lives in the field of up to over twenty years, so real-time and permanent monitoring of photovoltaic modules is essential. Many internal and external factors cause the power generation efficiency of the photovoltaic module to be low, such as mismatch between the photovoltaic modules themselves, mismatch between strings, manufacturing difference or installation difference of the photovoltaic modules or shadow shielding, maximum power tracking adaptability and other factors cause the conversion efficiency of the module to be reduced.

Referring to fig. 1, taking a common shadow blocking as an example, if a part of the photovoltaic modules is blocked by clouds or buildings or tree shadows or pollutants and the like, the part of the photovoltaic modules becomes a load by a power supply and does not generate electric energy any more, the local temperature of the photovoltaic modules at a position with a serious hot spot effect is usually higher, even exceeds 150 ℃, so that a local area of the photovoltaic modules is burnt or forms a dark spot, a welding spot is melted, a packaging body is aged, glass is exploded and corroded, and permanent damage such as dark spot, welding spot melting, packaging body aging, glass explosion and corrosion causes great hidden danger to the long-term safety and reliability of the photovoltaic modules, so that it is more important to avoid mismatch between the photovoltaic modules and find and locate faults in time.

Referring to fig. 1, in a battery string ST1, it is assumed that there are some photovoltaic modules operating exactly at their own maximum power point and in terms of a voltage versus power curve CV: it will be seen that the curve CV reflects that the maximum power of the photovoltaic module depends on the optimal operating current multiplied by the optimal operating voltage, and that there is a unique maximum power point for each photovoltaic module.

Referring to fig. 1, in a string ST2 of cells, it is assumed that there are some photovoltaic modules operating to the left of their own maximum power point and in terms of a voltage versus power curve CV: deviating from its unique maximum power point. Component mismatches occur when the electrical parameters of a single photovoltaic component in a string of groups are significantly different from the other photovoltaic components in the string of groups.

Referring to fig. 1, in a string STM, it is assumed that some photovoltaic modules operate to the right of their own maximum power point and in terms of a voltage versus power curve CV: deviating from its unique maximum power point. Component mismatches occur when the electrical parameters of a single photovoltaic component in a string of groups are significantly different from the other photovoltaic components in the string of groups.

Referring to fig. 1, a photovoltaic module can cause a mismatch loss problem: one of the sources of mismatch loss is due to the interconnection of photovoltaic modules, including series-parallel connections, which either do not have the same characteristics or experience different conditions leading to problems. The mismatch problem is a very serious problem because the output of a string of cells in the worst case is determined by the photovoltaic module with the lowest output among them. For example, when one pv module is shaded while the other pv modules in the string are not, the power generated by a good pv module is dissipated by the low performing pv module rather than being provided to the load side. This can result in very high local power dissipation and the resulting local heating can cause irreparable damage to the component.

Referring to fig. 1, the typical first year decay of a photovoltaic module is 5%, and the subsequent year does not exceed 0.8%, and the 25 year does not allow more than 20%. Unlike component mismatches, which are product inconsistencies at the factory, where photovoltaic component attenuation inconsistencies are caused over the years and attenuation is rather insidious and imperceptible, component mismatches, where a photovoltaic component operates to the left or right of its own maximum power point, are also related to attenuation. In addition, other reasons for component mismatch include shadow shielding, which is particularly prominent in distributed power stations in urban environments and mainly affected by fixed shadows such as surrounding buildings and trees. For rooftop power stations with less than ideal locations, it is very likely that periodic shadow shading on a daily basis results in a loss of 3-5% of the power production by the module mismatch.

Referring to fig. 1, let a photovoltaic module P1 be equipped with a local device J1. In the present embodiment, it is assumed that the local device is a photovoltaic junction box, the positive electrode of the photovoltaic module P1 is connected to the positive bus bar B1 by the local device J1, and the negative electrode of the photovoltaic module P1 is connected to the positive electrode of the photovoltaic module P2 by the local device J1 according to the connection function of the photovoltaic junction box. And if the local equipment is a photovoltaic junction box, the positive pole of the photovoltaic component P2 is connected to the negative pole of the P1 by the local equipment J2, and according to the connection function of the photovoltaic junction box, the negative pole of the photovoltaic component P2 is connected to the positive pole of the P3 by the local equipment J2. And similarly, if the local device is a photovoltaic junction box, the positive pole of the photovoltaic component P3 is connected to the negative pole of the P2 by the local device J3, and according to the connection function of the photovoltaic junction box, the negative pole of the photovoltaic component P3 is connected to the positive pole of the P4 by the local device J3. In analogy, a plurality of photovoltaic modules are connected in series to form a battery string capable of providing a higher voltage level. A photovoltaic junction box (PV junction box) which is a connector between the photovoltaic module and the bus bar is also called a solar junction box.

Referring to fig. 2, the management device 100 is exemplified by an inverter INVT that can invert the dc power on the bus to the desired ac power, noting that there are many other alternatives to the management device, such as a combiner box or a battery charger that charges a battery. The energy management device is explained by taking an inverter INVT as an example.

Referring to fig. 2, knowledge about inverter INVT: the photovoltaic inverter mainly plays a role in converting direct current emitted by a photovoltaic component into alternating current in a photovoltaic system, and besides, the inverter also plays important functions of detecting the running states of the component, a power grid and a cable, communicating with the outside, managing a system safety manager and the like.

Referring to fig. 2, in the photovoltaic industry standard NB32004-2013, there are over 100 strict technical parameters for inverters and each parameter is qualified for sale. The method is used for detecting a plurality of items such as protection connection, contact current, power frequency withstand voltage of solid insulation, rated input and output, conversion efficiency, harmonic wave and waveform distortion, power factor, direct current component, alternating current output side over/under voltage protection and the like of a photovoltaic grid-connected inverter product.

Referring to fig. 2, the photovoltaic modules P1-PN emit direct current, and after the direct current is changed by the inverter bridge, the magnitude and direction of the voltage and current are changed, but the voltage and current are not pure sine wave alternating current, and the current and voltage are not continuous, and contain a large amount of harmonics and can be changed into pure sine wave alternating current after being processed, which is filtering. The output harmonic of the photovoltaic inverter is divided into two parts, one part is higher harmonic and mainly comes from a modulation mode, and the other part is low harmonic and comes from switch dead zone effect, device parameter drift, sampling error, control parameter mismatching and the like.

Referring to fig. 2, a method of a photovoltaic power plant to address component mismatch and optimize power generation: photovoltaic modules (e.g., P1 of STM) operating to the left of the maximum power point are categorized and connected in series into strings of cells of a first type (e.g., ST 2). The dashed line with an arrow in the figure indicates switching P1 of the STM into string ST2 of cells. After the replacement and the switching, all the photovoltaic modules connected in series in the first battery pack string work on the left side of the maximum power point.

Referring to fig. 2, a method of photovoltaic power plant addressing component mismatch and optimizing power generation: photovoltaic modules (e.g., PN from ST 1) operating to the right of the maximum power point are sorted and connected in series into a string of a second type of cells (e.g., STM). The dashed line with an arrow in the figure indicates switching of PN from ST1 to string STM. After the replacement and the switching, all the photovoltaic modules connected in series in the second battery pack string work at the right side of the maximum power point.

Referring to fig. 2, a method of photovoltaic power plant addressing component mismatch and optimizing power generation: photovoltaic modules (such as P2 of ST 2) at the position of the maximum power point are classified and connected in series into a third type battery string (such as ST 1). The dashed line with an arrow in the figure indicates switching P2 of ST2 into the battery string ST1. After the replacement and the switching, all the photovoltaic modules connected in series in the third battery pack string just work at the maximum power point position.

Referring to fig. 2, a method of a photovoltaic power plant to address component mismatch and optimize power generation: when the first type battery pack string and the second type battery pack string are connected in parallel, power mismatch among photovoltaic modules with different maximum power point distributions is avoided. The third type of string may not be used because there may be fewer or nearly no photovoltaic modules at the very point of maximum power point.

Referring to fig. 2, a method of photovoltaic power plant addressing component mismatch and optimizing power generation: the third type of battery string is used for being connected with the first type of battery string and the second type of battery string in parallel. In order to avoid power mismatch between photovoltaic modules with different maximum power point distributions when the first to third types of battery packs are connected in series and in parallel.

Referring to fig. 2, if the product inconsistency at the time of shipment of the module meets the specifications, if the photovoltaic module still has a high attenuation consistency after undergoing a long attenuation, then a third type of battery string is typically used, since the photovoltaic module just at the maximum power point position will have a considerable proportion.

Referring to fig. 2, the inverter is supplied with power from at least the first-type and second-type battery strings (if the third-type battery string is used, the inverter is supplied with power from the first-type to third-type battery strings in common), the maximum power point of each photovoltaic module is dynamically analyzed in the process of performing maximum power tracking by the inverter, and secondary optimization is performed. The secondary optimization means that the string classification can be repeatedly executed on each photovoltaic module, and the execution times of the secondary optimization are not limited.

Referring to fig. 2, in an alternative embodiment, when performing quadratic optimization: those photovoltaic modules within the first type of string (e.g., the previously assigned first type of string ST 2) that have become operating again to the right of the maximum power point need to be re-categorized into a second type of string (e.g., the previously assigned second type of string STM).

Referring to fig. 2, in an alternative embodiment, when performing quadratic optimization: those photovoltaic modules within the second type of string (e.g., the previously assigned second type of string STM), which in turn become operating to the left of the maximum power point, need to be re-categorized into the first type of string (e.g., the previously assigned first type of string ST 2).

Referring to fig. 2, in an alternative embodiment, when performing quadratic optimization: those photovoltaic modules within the first type of string (e.g., the previously assigned first type of string ST 2) that have become operating at the maximum power point location need to be re-categorized into a third type of string (e.g., the previously assigned third type of string ST 1).

Referring to fig. 2, in an alternative embodiment, when performing quadratic optimization: those photovoltaic modules within the second type of string (e.g., the previously assigned second type of string STM) that have become operating at the maximum power point location need to be re-categorized into a third type of string (e.g., the previously assigned third type of string ST 1).

Referring to fig. 3, the energy management device 100 is omitted but an analyzer 150 is shown. Note that the energy management device is not eliminated from the power generation system, but is intentionally omitted based on the simplicity of the drawing. Other names for analyzers are processing modules or data analysis modules, etc.

Referring to fig. 3, module mismatch to support optimized power generation is connected in parallel by a plurality of battery strings ST1-STM and each battery string comprises a plurality of photovoltaic modules P1-PN connected in series, wherein: arranging a data acquisition module (integrated in the local device J1) for acquiring photovoltaic module parameters at one or more photovoltaic modules of each battery string; the parameters such as the output power and the output voltage corresponding to each photovoltaic module are all transmitted to the analyzer 150, and the analyzer 150 analyzes the power state of the photovoltaic module according to the parameters such as the output power and the output voltage transmitted by each photovoltaic module, and analyzes whether the photovoltaic module operates on the left side of the maximum power point or on the right side of the maximum power point, or just the maximum power point. The data acquisition module can also acquire the voltage and the current of the photovoltaic module and the parameters of whether the electric arc occurs and the like.

Referring to fig. 3, each local device J1-JN of the battery string ST1 transmits parameter data such as output power and output voltage of the photovoltaic module, which are acquired by each of the photovoltaic modules P1-PN, to the analyzer 150.

Referring to fig. 3, each local device J1-JN of the battery string ST2 transmits parameter data such as output power and output voltage of the photovoltaic module, which are acquired by each of the photovoltaic modules P1-PN, to the analyzer 150.

Referring to fig. 3, each local device J1-JN of the battery string STM transmits parameter data such as output power and output voltage of the photovoltaic module, which are acquired by each of the photovoltaic modules P1-PN, to the analyzer 150.

Referring to fig. 3, the photovoltaic module PN is equipped with a local device JN. In this embodiment, if the local device is a photovoltaic junction box, the positive electrode of the photovoltaic module PN is connected to the negative electrode of PN-1 by the local device JN, and the negative electrode of the photovoltaic module PN is connected to the negative bus B2 by the local device JN according to the connection function of the photovoltaic junction box. Therefore, different photovoltaic modules are connected in series and different local devices are connected in series, wherein N is a positive integer larger than 1.

Referring to fig. 3, in an alternative embodiment, in which a plurality of battery strings are connected in parallel and each battery string includes a plurality of photovoltaic modules P1 to PN connected in series, each photovoltaic module is configured with a local device that receives its output power, e.g., photovoltaic module P1 is configured with a local device J1 that receives the P1 output power, and further, for example, other photovoltaic modules PN are configured with a local device JN that receives PN output power. A plurality of photovoltaic modules, for example, a plurality of local devices J1 to JN corresponding to P1 to PN under any battery string are connected in series with each other by cables, which are usually conductive cables or referred to as power lines or power supply lines. In the present embodiment, it is set that the positive output terminal of the local device J1 is connected to the positive bus B1 and the negative output terminal of the local device JN is connected to the negative bus B2. After the output power of each photovoltaic module is subjected to power conversion or no power change by the local device corresponding to each photovoltaic module, the output powers of the plurality of photovoltaic modules are converged together and then sent to an energy collecting device mentioned later by the local device connected in series.

Referring to fig. 3, the divided voltage of the first-stage photovoltaic device P1 is V1. The divided voltage output by the similar second-stage photovoltaic module P2 is denoted as V2. And by analogy, the divided voltage output by the Nth-stage photovoltaic module PN is VN. The total bus voltage provided by any group of photovoltaic modules is about V through calculation _BUS Equal to V1+ V2+ V3+ \ 8230VN. The output power of each photovoltaic component is superposed on the bus bar, and the power collected by the bus bar is much higher than that of the single photovoltaic component.

Referring to fig. 3, the local equipment J1 uses a photovoltaic junction box in the present embodiment. The partial voltage V1 output by the photovoltaic module P1 to the cable can be represented by the output voltage of the local device J1, and the branch current output by the photovoltaic module P1 to the cable is represented by the current I1 output by the local device J1. The local device JN can also be characterized by the output voltage of the local device JN, for example, the divided voltage VN output by the photovoltaic module PN to the cable can be characterized by the current IN output by the local device JN, which is characteristic of the junction box. The cables are sometimes referred to as busbars.

Referring to fig. 3, IN an alternative embodiment, a plurality of local devices, e.g., J1 to JN, corresponding to a plurality of photovoltaic modules, e.g., P1 to PN, of the battery string are set IN series, the output current of the local device J1 configured by the monitored photovoltaic module P1 represents the branch current I1 supplied by the photovoltaic module P1 to the cable, the output current of the local device J2 configured by the photovoltaic module P2 represents the branch current I2 supplied by the photovoltaic module P2 to the cable, the output current of the local device JN configured by the photovoltaic module PN represents the branch current IN supplied by the photovoltaic module PN to the cable, and so on.

Referring to fig. 4, if the local device is a voltage converter, for example, each of the multi-stage photovoltaic modules P1-PN is configured with a voltage converter, the output power of the voltage converters corresponding to the multi-stage photovoltaic modules P1-PN is required to be superimposed on the dc bus and thus used as the bus power. In this case, the plurality of voltage converters are connected in series with each other. The local device J1, such as a voltage converter, converts the electric energy captured from the corresponding photovoltaic module P1 into its own output power, and the local device J1, such as a voltage converter, further performs processing such as voltage boosting, voltage reducing, or voltage boosting on the initial voltage of the corresponding photovoltaic module P1, and then outputs the initial voltage. The DC/DC converter serving as the voltage converter may be a step-up type voltage converter or a step-up type switching power supply, a step-down type voltage converter or a step-down type switching power supply, a step-up/step-down type voltage converter, or a step-up/step-down type switching power supply. The local device has a voltage regulation function of boosting or reducing voltage. According to the same principle, the remaining other local devices JN such as the voltage converter convert the electric energy extracted from the corresponding photovoltaic module PN into their own output power, and the local devices JN such as the voltage converter further perform the processing of boosting, stepping down, or stepping up and stepping down the initial voltage of the corresponding photovoltaic module PN and then output the initial voltage.

Referring to fig. 4, the local device is a voltage converter that performs voltage conversion on the initial voltage of the component. In the series relation, the partial voltage provided by the first-stage photovoltaic assembly P1 to the cable is represented by the output voltage V1 of the local equipment J1, and the branch current provided by the first-stage photovoltaic assembly to the cable is represented by the current I1 output by the local equipment J1. The output voltage V1 is a voltage output by the converter, i.e., the local device J1, after performing conversion such as voltage boosting or voltage dropping. The local device J1 is in this example a voltage converter for performing a voltage conversion on the initial voltage of the photovoltaic module P1. In this example, the output voltage V1 may be higher than the initial voltage output by the corresponding photovoltaic module P1 or lower than the initial voltage output by the photovoltaic module P1. A capacitor is often connected between a group of output ends of the voltage converter, that is, the positive output end and the negative output end of the local device J1, so as to ensure that the output voltage of the voltage converter is relatively smooth and reduce ripples. The positive and negative outputs of the local device herein or below may be replaced by the terms first and second output, respectively.

Referring to fig. 4, the local device is a voltage converter that performs up-down conversion on the initial voltage of the component. IN the series connection, the partial voltage supplied to the cable by the last photovoltaic module PN is characterized by the output voltage VN of the local device JN and the branch current supplied to the cable by the last photovoltaic module PN is characterized by the local device JN output current IN. The output voltage VN is a voltage output by the converter, that is, the local device JN, after performing conversion such as voltage boosting or voltage dropping. The local device JN is in this example a voltage converter for performing voltage conversion on the initial voltage of the photovoltaic module PN. The output voltage VN in this example can be either higher or lower than the initial voltage output by the corresponding photovoltaic module PN.

Referring to fig. 4, assume that the output voltage of the local device J1 is V1. Similarly assume that the output voltage from local device J2 is denoted as V2. And so on, the voltage output by the nth stage local device JN is VN. The total bus voltage provided by any group of photovoltaic modules is about V through calculation _BUS Equal to V1+ V2+ V3+ \ 8230VN. The output power of each photovoltaic module is superposed on the bus bar, and the power collected by the bus bar is much higher than that of the single photovoltaic module.

Referring to fig. 4, the energy collecting device used by the management apparatus 100 may be other energy collecting devices besides the inverter INVT, such as a junction box CB or the like that typically collects energy of photovoltaic modules, or may be various chargers or boost converters or the like that charge storage batteries. The management equipment can raise the voltage level of the bus by using the boost converter, and then carries out inversion conversion on the bus voltage with higher voltage level.

Referring to fig. 3, a plurality of battery strings are connected in parallel and each battery string includes a plurality of photovoltaic modules connected in series by cables, for example, a first battery string illustrated in the upper half of the drawing includes a plurality of photovoltaic modules P1 to PN connected in series by cables, and a second battery string illustrated in the lower half of the drawing includes a plurality of photovoltaic modules P1 to PN connected in series by cables. More parallel battery strings like STM are not shown in the figure.

Referring to fig. 5, the data acquisition module is used for acquiring one or more items of target data of the photovoltaic module. The target data collected by the data collection module comprise initial voltage and initial current of the photovoltaic module, and output voltage or output current output to the bus by local equipment. The data acquisition module may use a voltage detection module, such as a voltage detector VT or a voltage sensor, which is commonly used in the industry, to detect the initial voltage of the photovoltaic module, and a voltage detection module, such as a voltage detector VT or a voltage sensor, which is commonly used, to detect the output voltage of the local device. The current detector CT or the current sensor may be used to detect the initial current of the photovoltaic module, and the current detector CT or the current sensor may be used to detect the output current of the local device. The initial voltage and initial current of the photovoltaic module are delivered to the local device and the output voltage and output current of the local device are delivered to the cable. The data acquisition module may include a temperature sensor for monitoring the ambient temperature in which the photovoltaic module is located, or an irradiance meter for monitoring the effective irradiance of solar irradiance in the ambient environment in which the photovoltaic module is located. The target data may also be referred to as operating parameters, and the data types include, but are not limited to, voltage, current, temperature, output power, effective light radiation, etc. of the photovoltaic module.

Referring to fig. 5, the arc signal belongs to a class of data, so when the data acquisition module is used to acquire one or more target data of the photovoltaic module, the target data includes arc data. In an alternative embodiment, the data acquisition module comprises an arc sensor or a fault arc detector (arc fault sensor). The arc sensor may be integrated with a photovoltaic junction box (e.g., JN) and the photovoltaic junction box (e.g., JN) may then be used to connect the photovoltaic module PN to the battery string STM. An arc sensor, not shown, is used to detect an arc condition at the photovoltaic module PN.

Referring to fig. 5, the local devices J1 to JN include the above-mentioned current detector CT or similar current detection module such as a current sensor to detect the output current of the photovoltaic module or the local device. For example, the branch current I1 provided by each monitored photovoltaic module, for example P1, to the cable is measured in any battery string, and since the photovoltaic module P1 is not directly connected to the cable but indirectly connected to the cable through the local device J1, the branch current provided by the photovoltaic module P1 to the cable is represented by the output current I1 of the local device J1. The initial current and initial voltage of the photovoltaic module P1 are delivered to the local device J1 and the latter receives the P1 output power. If the branch current IN supplied to the cable by each monitored photovoltaic module, for example, PN, is measured IN the battery string, and the branch current supplied to the cable by the photovoltaic module PN is represented by the output current IN of the local device JN because the photovoltaic module PN is not directly connected to the cable but indirectly connected to the cable through the local device JN. The initial current and initial voltage of the photovoltaic module PN are delivered to the local device JN and the latter receives the PN output power

Referring to fig. 5, the native device JN includes a controller IC1. Many types of controllers IC1 currently have their own data acquisition modules that can collect the aforementioned target data. For example, the controller IC1 is also called a microprocessor and allows it to have a function of a temperature sensor or a voltage current detection module. The controller IC1 may be provided with an additional data acquisition module to collect the target data, provided that it does not have a data acquisition module. Usually, the controller IC1 can send out the target data by controlling the communication module CM1 after knowing the parameter information such as the target data. The communication mechanism of the communication module CM1 includes two types of wired communication and wireless communication: for example, all existing wireless communication schemes such as WIFI, ZIGBEE, 433MHZ communication, infrared or bluetooth, etc. may be adopted, and for example, a scheme of power line carrier communication may be intentionally adopted. In an alternative embodiment of the present application, the communication module CM1 includes a power line carrier modulator, and the power line carrier modulator is configured to transmit the target data to the data receiving side by means of a power line carrier. A coupling element 10 is shown for coupling a power line carrier emitted by a power line carrier modulator to a bus, the coupling element 10 being, for example, a transformer with a primary secondary winding or, for example, a signal coupler with a coupling coil. The coupling transformer can be used, for example, to transmit a power line carrier to the primary winding and the secondary winding to the bus or bus branch as part of the bus, the carrier being transmitted to the bus by the coupling of the primary and secondary windings. A typical method of using a signal coupler with a magnetic loop and a coupling coil is to pass a bus or a bus branch directly through the magnetic loop of the signal coupler around which the coupling coil is wound, and a power line carrier is transmitted to the coupling coil and is sensed from the power bus, so that contactless signal transmission can be performed. In summary, all signal coupling schemes disclosed in the prior art can be adopted as the coupling element, and injection type inductive coupler technology, cable clamping type inductive coupler technology, switchable full-impedance matching cable clamping type inductive coupler and the like are all alternatives of the application. The general principle is that the controller delivers the target data to the communication module and the communication module transmits the target data to the data receiver through wired or wireless means.

Referring to fig. 5, regarding wired communication and wireless communication, considering that the geographical environment of the photovoltaic module is a building roof or a desert area or a suburban mountain, the wireless communication usually brings high additional cost and is inferior in reliability of durability, and after all, the general life of the photovoltaic module is as long as more than twenty years, so the use of power line carrier for communication between the master node and the slave node and between the slave node and the slave node is a preferable option. The frequencies of the power line carrier signals that are allowed to be emitted by different local devices are also different, but wireless communication is also an option.

Referring to fig. 5, analyzer 150, which includes controller IC2 and communication module CM2, also allows for the inclusion of an associated carrier signal coupling element 20 for sensing a power line carrier signal from the bus, noting that the local device is sending and loading a power line carrier signal onto the bus or cable at the photovoltaic module, while the analyzer is sensing and capturing a power line carrier signal returned from the cable to the analyzer. The communication module and the coupling element are sometimes integrated, as they comprise any of the types of rogowski air coil sensors or high frequency sensors, codecs or shunts, etc. It is worth clarifying that the local equipment is also the same as the analyzer described above: the wireless communication terminal has a data receiving function of wired or wireless communication. The same is true of the analyzer as the local device described above: the wireless communication device has a data transmission function of wired or wireless communication. For example, when the analyzer actively polls different local devices and requests the local devices to receive polling signals, it is necessary to return target data collected and stored by the analyzer to the analyzer, and the analyzer is equivalent to a master node and each local device is equivalent to a slave node. The local device is illustrated and described in this example with the photovoltaic junction box as an optional example, although the wired and wireless communication functions provided in the local device and the analyzer are also applicable to this example.

Referring to fig. 5, the analyzer 150 may be integrated directly inside the energy management device 100. The analyzer 150 may be provided separately without being integrated with the energy management device 100.

Referring to fig. 5, the analyzer 150 has a current detection module such as the conventional current detector CT or current sensor mentioned above to detect the string current IS of the battery string. The string current is a current flowing through the battery string, and is also a current flowing through each of the photovoltaic modules P1 to PN or a current flowing through each of the local devices J1 to JN.

Referring to fig. 5, after the analyzer 150 and the local devices J1 to JN establish a communication mechanism, the branch current provided by each photovoltaic module to the cable is sent to the analyzer 150 by the local device configured to the branch current, and one of the core tasks of the analyzer 150 is to analyze the variation of the output power of the photovoltaic module and the variation of the output voltage of the photovoltaic module, where the variation of the output power and the variation of the output voltage of the photovoltaic module can be provided by the data acquisition module. For example, the data acquisition module acquires the output power at two moments and performs difference to obtain the power variation, for example, the data acquisition module acquires the output voltage at two moments and performs difference to obtain the variation of the output voltage of the photovoltaic module. These tasks may be performed by the analyzer 150.

Referring to fig. 5, this example is a photovoltaic junction box. The photovoltaic junction box may be replaced with a shutdown device that disconnects the photovoltaic module from the cable or that reconnects the disconnected photovoltaic module to the cable, the photovoltaic junction box may be replaced with a power optimizer that sets the photovoltaic module at a maximum power point, or the photovoltaic junction box may be replaced with a voltage converter that performs voltage conversion on an initial voltage of the photovoltaic module. The solution of fig. 5 is applicable to the examples of fig. 6 to 8.

Referring to fig. 6, in a shutdown apparatus supporting rapid shutdown management of a photovoltaic module, a local device JN, such as a shutdown apparatus, which can control whether the photovoltaic module is shutdown or not, is taken as an example. The shutdown management goal that the local device JN, such as the circuit of the shutdown apparatus, is expected to achieve is to determine whether it is necessary to shutdown the photovoltaic module in time: photovoltaic systems installed or built into buildings must include a quick shut-off function, reducing the risk of electrical shock to emergency personnel. Although the component shutdown device is described by taking as an example a component shutdown device that implements a shutdown function, in fact, the component shutdown device functionally integrates at least a data acquisition function and a component shutdown function. Explanation on the component shutdown function: the local device JN, such as a shutdown device, may disconnect the corresponding photovoltaic module PN from the cable and not supply power to the bus bar, and the local device JN, such as a shutdown device, may restore the disconnected photovoltaic module PN to the cable and supply power to the bus bar again. For example, a positive output of native device J1 is connected to positive bus B1 and a negative output of native device JN is connected to negative bus B2. And the positive output end of the latter local device in the plurality of series-connected local devices is connected to the negative output end of the adjacent former local device, or the positive output end of the latter local device in the plurality of stages of local devices is connected to the negative output end of the adjacent former local device, so that the plurality of local devices are connected in series to form a battery string. Each photovoltaic module in the battery string is configured with a local device receiving the output power thereof, for example, any one photovoltaic module PN in the battery string is configured with a local device JN receiving the output power of the photovoltaic module PN, and a plurality of local devices corresponding to the plurality of photovoltaic modules P1 to PN in any battery string are connected in series with each other, for example, J1 to JN in series, through cables. The connection relationships of the local devices here apply to the examples of fig. 1-6.

Referring to fig. 6, the data acquisition module may be integrated with a shutdown device (e.g., JN) and the shutdown device is now used to remove individual photovoltaic modules PN from the string STM or to reconnect the removed photovoltaic modules PN back into the string STM. The data acquisition module is used for detecting various parameters of the photovoltaic module: the data acquisition module is used for collecting voltage and current parameters or target data and the like at the photovoltaic module, so that the voltage and the current of the photovoltaic module can be converted into the variable quantity of the output power of the photovoltaic module and the variable quantity of the output voltage of the photovoltaic module.

Referring to fig. 6, a bypass diode or a complementary switch may be disposed between the positive output terminal (first output terminal) and the negative output terminal (second output terminal) of the native device JN. The complementary switch is a switch complementary to switch S1: if switch S1 is on then its complementary switch is turned off and switch S1 is off then its complementary switch is turned on. The significance of arranging the bypass diode or complementary switch is to prevent the battery string from forming an open circuit at the local device JN. The bypass diode or the complementary switch of the local device JN is switched on if the photovoltaic module PN is switched off. If the photovoltaic module PN is reconnected to the cable or in the battery string, the bypass diode or complementary switch is turned off.

Referring to fig. 6, the local device JN may set a switch S1 between the negative electrode of the photovoltaic module PN and the conductive cable or may alternatively set a switch S1 between the positive electrode of the photovoltaic module PN and the conductive cable. The local device JN collects one or more target data of the photovoltaic module through the data collection module, and if the target data are found to be abnormal, the local device JN can be controlled by the controller IC1 to turn off the photovoltaic module PN, for example, the controller IC1 is used to operate to turn off the switch S1, and the controller IC1 can drive or control the switch S1 to turn off whether the initial voltage or the initial current of the photovoltaic module is abnormal or the output voltage or the output current of the local device to the cable is abnormal. Based on the communication mechanism established between the local device and the analyzer, if the instruction sent by the analyzer 150 to the local device JN includes a turn-off instruction, the local device will actively drive or control the switch S1 to turn off when receiving such an instruction. Meanwhile, in other optional embodiments, shutdown management is also supported, for example, the local device J1 supporting fast shutdown of the photovoltaic module P1 is used to operate the turn-off or turn-on of the shutdown switch S1 configured for the photovoltaic module, so as to control whether the photovoltaic module P1 is turned off or not. And so on, other optional examples also support shutdown management, such as the local device J2 supporting the rapid shutdown of the pv module P2 is used to operate the shutdown switch S1 of the pv module configuration to turn off or on to control whether the pv module P2 is turned off or not. The local device is illustrated as an optional example in this example as a shut-off device, although the wired and wireless communication functions of the local device and the analyzer described above are also applicable to this example, and both the local device and the analyzer have bidirectional communication capabilities. The shutdown device removes the photovoltaic module from the battery string or restores the photovoltaic module in the removed state to be connected to the battery string again.

Referring to fig. 6, the way in which the analyzer 150 reads the respective target data of the photovoltaic modules P1-PN, such as the voltage to the cable and the branch current to the cable, is: the analyzer 150 polls the series of local devices J1-JN corresponding to the photovoltaic modules P1-PN in turn, and when the analyzer 150 polls any one of the local devices, such as JN, the queried local device, such as JN, needs to return the target data of the corresponding photovoltaic module PN to the analyzer 150. This data reading mode is now described, for example: when the controller IC2 of the analyzer 150 queries the local device, such as J1, the controller IC1 of the queried local device, such as J1, needs to return the target data of the photovoltaic module P1 to the controller IC2. Continuing by way of example, this manner of data reading: when the controller IC2 of the analyzer 150 queries the local device, such as J2, the controller IC1 of the queried local device, such as J2, needs to return the target data of the photovoltaic module P2 to the controller IC2. In summary, such data reading can be considered as: the controllers configured by the analyzer, i.e., the master node, sequentially poll the controllers configured by the local devices, i.e., the slave nodes, respectively, and when the analyzer polls any one of the local devices, the controller of the queried local device returns target data of a corresponding photovoltaic module, such as a voltage of the photovoltaic module and an output current of the photovoltaic module, to the controller configured by the analyzer. To avoid confusion, the controller of the local device may be referred to as the first controller and its communication module may be referred to as the first communication module, while the controller of the analyzer may be referred to as the second controller and its communication module may be referred to as the second communication module. Other alternatives to the controller are: a field programmable gate array or a complex programmable logic device or a field programmable analog gate array or a semi-custom ASIC or a processor or a microprocessor or a digital signal processor or an integrated circuit or a software firmware program stored in a memory, etc. The polling data reading method is also applicable to a shutdown device, a power optimizer, a voltage converter and the like besides the illustrated photovoltaic junction box.

Referring to fig. 7, each of the pv modules P1-PN is configured with a voltage converter, which is also called a switching regulator and is most commonly represented by switching power supply circuit topologies such as buck converter, boost converter, buck-boost converter, etc. The controller IC1 of the local device JN is usually designed as a driving chip, and the controller drives a voltage converter or a converting circuit to convert the input voltage drawn from the photovoltaic module P1 into an output voltage, the voltage converter is also called a power stage circuit, the controller IC1 is also called a power controller, and the controller IC1 is most commonly a power management controller or a power management chip for managing the switching power supply in the industry. This example allows the local device to simply perform a basic step-down conversion or step-up conversion on the initial voltage of the photovoltaic module, for example, the output voltage of the local device is regarded as the partial voltage of the output of the photovoltaic module to the bus, and the initial voltage of the photovoltaic module is transmitted to the local device, and the output voltage of the local device is the voltage obtained by stepping-down or stepping-up the initial voltage of the photovoltaic module. The local device does not need power optimization at this time.

Referring to fig. 7, the data collection module is integrated with a voltage converter (e.g., JN) and the voltage converter is used to perform a step-up voltage conversion or a step-down voltage conversion on the initial voltage of the photovoltaic module PN. The data acquisition module is used for collecting voltage and current parameters or target data and the like at the photovoltaic module, so that the voltage and the current of the photovoltaic module can be converted into the variable quantity of the output power of the photovoltaic module and the variable quantity of the output voltage of the photovoltaic module.

With reference to fig. 7, the issues of concern in distributed or centralized photovoltaic power plants are: shadow occlusion causes mismatches among numerous photovoltaic modules. The problem is that the battery output characteristics of the photovoltaic module are represented by the fact that the output voltage and the output current are closely related to external factors such as light intensity and ambient temperature, and the uncertainty of the external factors causes the corresponding voltages of the maximum output power and the maximum power point to change along with the change of the external factors. For example, the power output by the photovoltaic module has randomness and severe fluctuation, and the random uncontrollable characteristic has high probability of causing large impact on the power grid and can also cause negative influence on important load operation. Based on these doubts, achieving maximum power point tracking of photovoltaic modules in consideration of external factors is a core goal of the industry to maximize energy and revenue.

Referring to fig. 7, the principle and features of a conventional MPPT method for power optimization: for example, in the early output power control for photovoltaic modules, the Voltage feedback method Constant Voltage Tracking is mainly used, and this Tracking method ignores the influence of temperature on the open-circuit Voltage of the solar cell, so the open-circuit Voltage method and the short-circuit current method are proposed, and their common property is basically very similar to the maximum power point of the solar cell. In order to more accurately capture the maximum power point, a disturbance observation method, a duty ratio disturbance method, a conductance increment method and the like are proposed. The disturbance observation method is characterized in that the current array power is measured, then a small voltage component disturbance is added to the original output voltage, the output power is changed, the changed power is measured, the power before and after the change is compared, the power change direction can be known, if the power is increased, the original disturbance is continuously used, and if the power is reduced, the original disturbance direction is changed. The duty ratio disturbance working principle is as follows: the interface between the photovoltaic array and the load generally adopts a voltage converter controlled by a pulse width modulation signal, so that the input and output relationship of the converter can be adjusted by adjusting the duty ratio of the pulse width modulation signal, and the function of impedance matching is realized, and therefore, the magnitude of the duty ratio substantially determines the magnitude of the output power of the photovoltaic cell. The incremental conductance method is a special way to the disturbance observation method, the biggest difference is only in the logical judgment formula and the measurement parameters, although the incremental conductance method still changes the output voltage of the photovoltaic cell to reach the maximum power point, the logical judgment formula is modified to reduce the oscillation phenomenon near the maximum power point, so that the incremental conductance method is suitable for the climate with instantaneous change of the sunlight intensity and the temperature. Practical measurement methods, fuzzy logic methods, power mathematical models, intermittent scanning tracking methods, optimal gradient methods or three-point gravity center comparison methods and the like belong to the most popular maximum power point tracking methods. Therefore, the MPPT algorithm used in the photovoltaic energy industry is diversified, and repeated description is omitted in the application.

Referring to fig. 7, each of the pv modules P1-PN is configured with a voltage converter, but the voltage converter is not only a simple voltage converter but also an optimizer because it has a power optimization function. Each power optimizer is used to set the initial current and initial voltage of the photovoltaic module corresponding thereto at the maximum power point. For example, a local device J1 such as a power optimizer is shown to set the corresponding pv module P1 at the maximum power point, a local device J2 such as a power optimizer is shown to set the corresponding pv module P2 at the maximum power point, and a local device JN such as a power optimizer is shown to set the corresponding pv module PN at the maximum power point. The power optimizer performs a power optimization function on the photovoltaic module, and in this example, the controller IC1 of the local device JN may be configured to operate the power optimizer to perform voltage conversion actions such as voltage boosting or voltage dropping or voltage boosting, so as to set the initial current and the initial voltage of the photovoltaic module, that is, the input voltage and the input current of the local device to the maximum power point of the photovoltaic module PN. The local equipment may also be provided with power management functions to maximize the efficiency of the photovoltaic module.

Referring to fig. 7, the power optimizer is a dc-to-dc converter, also a single component level battery maximum power tracking device. After the single component is optimized to the maximum power by the power optimizer, the collected total power is transmitted to the inverter to be converted from direct current to alternating current, and then the converted total power is supplied to local use or direct grid connection. The inverter may typically be a pure inverter device without maximum power tracking or an inverter device equipped with two-stage maximum power tracking. The main topology of mainstream power optimizers is for example the conventional BUCK or BOOST or BUCK-BOOST or CUK circuit architecture.

Referring to fig. 7, the data acquisition module is integrated with a power optimizer (e.g., JN) and the power optimizer is then used to set the photovoltaic module PN at the maximum power point. The data acquisition module is used for collecting voltage and current parameters or target data and the like at the photovoltaic module: therefore, the voltage and the current of the photovoltaic module can be converted into the variable quantity of the output power of the photovoltaic module and the variable quantity of the output voltage of the photovoltaic module.

Referring to FIG. 8, photovoltaic modules P1-PN are connected in series to supply power to the bus bars, and the output power and output voltage of the photovoltaic modules are collected at each of the photovoltaic modules P1-PN. According to the same principle, the output power and the output voltage of the photovoltaic module P1 are collected by the local device J1, the output power and the output voltage of the photovoltaic module P2 are collected by the local device J2, and so on, the photovoltaic module PN can also be known to be collected by the local device JN. And so on.

Referring to fig. 8, the local device J1 sends the output power and the output voltage of the photovoltaic module P1 collected at the photovoltaic module P1 or the output voltage and the output current of the photovoltaic module P1 to the analyzer 150.

Referring to fig. 8, the local device J2 sends the output power and the output voltage of the photovoltaic module P2 collected at the photovoltaic module P2 or the output voltage and the output current of the photovoltaic module P2 to the analyzer 150.

Referring to fig. 8, the local device JN transmits the output power and the output voltage of the photovoltaic module PN or the output voltage and the output current of the photovoltaic module PN collected at the photovoltaic module PN to the analyzer 150. After the data acquisition module acquires the output power and the output voltage of the corresponding photovoltaic module, the output power variation of the photovoltaic module and the variation of the output voltage of the photovoltaic module can be analyzed by local equipment, target data can also be given to the analyzer 150, and then the analyzer analyzes the output power variation of the photovoltaic module and the variation of the output voltage of the photovoltaic module. The method for analyzing whether the photovoltaic module works on the left side or the right side of the maximum power point by the local equipment belongs to edge side data processing, and the method for analyzing whether the photovoltaic module works on the left side or the right side of the maximum power point by the analyzer is similar to cloud side data processing.

Referring to fig. 8, after the analyzer 150 knows the output voltage and output current results of each photovoltaic module, the analyzer can analyze whether the photovoltaic module operates on the left side of the maximum power point or on the right side of the maximum power point according to the output voltage and output current results transmitted by each battery string ST 1-STM.

Referring to fig. 8, in the photovoltaic module power-voltage curve, the photovoltaic module has only one maximum output power point under the same environmental conditions. On the left side of the maximum power point, the output power of the photovoltaic module represented by a curve at the moment shows a rising trend along with the rising of the output voltage of the photovoltaic module; after the maximum power point is reached, the output power of the photovoltaic module represented by the curve at the moment is rapidly reduced on the right side of the maximum power point, and the output power of the photovoltaic module represented by the curve at the moment is in a descending trend along with the increase of the output voltage of the photovoltaic module. Typically, the rate of such a drop is much greater than the rate of rise. It is preferable to stabilize the output voltage of the photovoltaic module around the unique voltage corresponding to its maximum power point.

Referring to fig. 8, for example, a positive output terminal of the local device J1 is connected to the positive bus B1 and a negative output terminal of the local device JN is connected to the negative bus B2, and a positive output terminal of a subsequent local device among the plurality of local devices connected in series is connected to a negative output terminal of an adjacent previous local device, or a positive output terminal of a subsequent local device among the plurality of local devices connected in series is connected to a negative output terminal of an adjacent previous local device, thereby connecting the plurality of local devices in series to form a battery string. Each photovoltaic module in the battery string is configured with a local device receiving the output power thereof, for example, any one photovoltaic module PN in the battery string is configured with a local device JN receiving the output power of the photovoltaic module PN, and a plurality of local devices corresponding to the plurality of photovoltaic modules P1 to PN in any battery string are connected in series with each other, for example, J1 to JN in series, through cables.

Referring to fig. 8, each photovoltaic module PN is configured with a local device JN for retrieving parameter information thereof, and an analyzer 150 for collecting at least parameter conditions of each battery string is configured on the bus bar or the cable. Communication is established between the local equipment and the analyzer, the local output voltage and current condition of each photovoltaic module JN is sent to the analyzer by the local equipment configured by the photovoltaic module JN, and the analyzer 150 judges the maximum power point position of the module at the battery string ST 1-STM. And judging the photovoltaic module working at the left side of the maximum power point, the photovoltaic module working at the right side of the maximum power point or judging the photovoltaic module just working at the maximum power point, and classifying the photovoltaic modules.

Referring to fig. 5, the local device JN includes a first controller IC1 and a first communication module CM1 and the analyzer 150 includes a second controller IC2 and a second communication module CM2; and the first controller IC1 of the local device JN transmits the target parameter result of the corresponding photovoltaic module PN to the analyzer 150 using the first communication module CM 1. The second controller IC2 of the analyzer receives the target parameter results for each photovoltaic module by the second communication module CM2, and the second controller determines the power status (e.g., left and right, etc.) at each photovoltaic module. The mode of communication between the local device JN and the analyzer 150 includes at least power line carrier communication, wireless communication, or the like.

Referring to fig. 8, a method of photovoltaic power plant addressing component mismatch and optimizing power generation: photovoltaic modules operating on the left side of the maximum power point are classified and connected in series into a first type of string (e.g., ST 2) and photovoltaic modules operating on the right side of the maximum power point are classified and connected in series into a second type of string (e.g., STM) so that when the first type of string and the second type of string are connected in parallel, power mismatch between photovoltaic modules (ST 1-STM) having different maximum power point distributions is avoided and the best effort is made to operate the photovoltaic system in the optimal power point state.

Referring to fig. 8, a method of photovoltaic power plant addressing component mismatch and optimizing power generation: photovoltaic modules operating at the left side of the maximum power point are categorized and connected in series into a first type of string (e.g., ST 2), and photovoltaic modules operating at the right side of the maximum power point are categorized and connected in series into a second type of string (e.g., STM), with photovoltaic modules operating at the right side of the maximum power point being categorized and connected in series into a third type of string (e.g., ST 1). The third type battery string is used for being connected with the first type battery string and the second type battery string in parallel, and supplies power to the bus and the inverter INVT together.

Referring to fig. 8, a method of photovoltaic power plant addressing component mismatch and optimizing power generation: analyzing a property sign of a variation in output power of the photovoltaic module to a variation in output voltage of the upper photovoltaic module, wherein photovoltaic modules having a property sign of positive sign are connected in series into a category of battery string (for example, battery string ST 2); in addition, photovoltaic modules with a property sign of negative sign are connected in series into another category of battery string (e.g., battery string STM). In order to avoid power mismatch between photovoltaic modules with different maximum power point distributions when different types of strings are connected in parallel with each other.

Referring to fig. 8, a method of a photovoltaic power plant to address component mismatch and optimize power generation: photovoltaic modules that happen to operate at the maximum power point location are categorized and connected in series into other categories of battery strings (e.g., battery string ST 1). Three different classes of battery strings are provided in series connection (e.g., ST1-STM series connection).

Referring to fig. 8, the inverter is supplied with power from at least different types of battery strings, and the maximum power point of each photovoltaic module is dynamically analyzed and secondary optimization is performed during the maximum power tracking performed by the inverter: photovoltaic modules with the property signs changed into positive signs (such as certain photovoltaic modules with the property signs changed into positive signs originally belonging to STMs) are classified into the battery string classes connected in series (such as the battery string ST 2), and photovoltaic modules with the property signs changed into negative signs (such as the photovoltaic modules with the property signs changed into negative signs originally belonging to ST 2) are classified into the battery string classes connected in series (such as the battery string STM).

Referring to fig. 8, the inverter is supplied with power from at least different types of battery strings, and the maximum power point of each photovoltaic module is dynamically analyzed and secondary optimization is performed during the maximum power tracking performed by the inverter: the method comprises the steps of classifying photovoltaic modules in different battery string categories into battery string categories (such as battery string ST 1) connected in series, and classifying photovoltaic modules in different battery string categories into battery string categories (such as battery string ST 1) connected in series, wherein the photovoltaic modules are operated at the maximum power point positions (such as photovoltaic modules in different attribute symbols of ST 2).

Referring to fig. 8, in fact, the method is limited by complicated operation environments, such as accidental factors of the shading position of the photovoltaic module, the gradual change of the cloud or the sunlight, the temperature change, and the like. These factors result in considerable randomness in the determination of whether a photovoltaic module is operating to the left or right of the maximum power point. The difficult problem is that: how to restrain the photovoltaic module which originally works on the left side of the maximum power point from sporadically drifting to the right side of the maximum power point and restrain the photovoltaic module which originally works on the right side of the maximum power point from sporadically drifting to the left side of the maximum power point. The causes of sporadic drift include at least a series of predetermined sporadic factors such as the aforementioned shadowing or cloud cover or irradiance variation.

Referring to fig. 8, in an alternative example, the phase "determining that the photovoltaic module operates at the left or right of the maximum power point from the sign of the nature of the variation of the output power of the photovoltaic module to the variation of the output voltage of the photovoltaic module" requires dynamically adjusting the time interval at the inverter during which the inverter performs maximum power optimization MPPT, the time interval during which the inverter performs maximum power optimization being dynamically fluctuated at a high frequency at this phase (while other time intervals are not dynamically adjusted). Thereby forcing the actual output voltage of the photovoltaic module to be in proportion to the unique voltage corresponding to the maximum power point of the photovoltaic module at this stage, so as to greatly bounce. Thereby shielding the accidental drift of the photovoltaic module caused by the accidental factors. At this stage, the photovoltaic modules approaching the left side of the maximum power point are divided into first-class battery strings, and the photovoltaic modules approaching the right side of the maximum power point are divided into second-class battery strings. One of the effects of dynamic fluctuation of time intervals: the method and the device can inhibit the photovoltaic modules which originally work at the left side of the maximum power point from sporadically drifting to the right side of the maximum power point and inhibit the photovoltaic modules which originally work at the right side of the maximum power point from sporadically drifting to the left side of the maximum power point. Or otherwise: the method can be used for inhibiting the photovoltaic module which originally works on the left side of the maximum power point from sporadically drifting to the maximum power point position of the photovoltaic module, and inhibiting the photovoltaic module which originally works on the right side of the maximum power point from sporadically drifting to the maximum power point position of the photovoltaic module. It is noted that in alternative embodiments, the proportional relationship described above allows positive and negative bounces between positive and negative numbers, in addition to purely absolute value bounces in magnitude.

Referring to fig. 8, if the time interval during which the inverter performs MPPT is dynamically adjusted at the inverter, the multi-stage photovoltaic modules are connected in series using a multi-stage power optimizer in the preferred example. At this time, the power optimizers adaptively respond to the bus voltage change caused by the maximum power optimization executed by the inverter, and each power optimizer synchronously changes the output voltage and the output current of the corresponding photovoltaic module, which are equivalent to the bounce amplitude and the bounce frequency which aggravate the proportional relation between the actual output voltage of the photovoltaic module and the unique voltage at the maximum power point of the photovoltaic module. It is possible to specify individual photovoltaic modules in their respective category robustly already before the onset of sporadic factors. In contrast, if multiple photovoltaic modules are connected in series using multiple photovoltaic junction boxes or multiple turn-off devices or multiple voltage converters, there is nearly no power optimizer to connect the multiple photovoltaic modules in series to achieve the aforementioned efficacy.

Referring to fig. 8, in an alternative embodiment, part of the pv system may not be the power generation efficiency caused by external factors such as the hardware and software design of the power generation components or the system integration, but rather may be caused by non-obvious internal factors such as the series-parallel mismatch of the pv modules, so that the actual operating efficiency and power generation efficiency of the pv modules and the pv inverters of the pv system are always far from the calibrated rated efficiency and efficiency. The scheme well mentioned in the application provides a method for solving component mismatch (including series-parallel mismatch) and optimizing power generation of the photovoltaic power station. The method takes organic combination of power optimization and component mismatch into consideration, integrates the advantages in various aspects, and prevents a single aspect from obtaining the advantages and other aspects from being subjected to toggle: for example, while addressing power optimization, this results in component mismatch, and while trying to balance photovoltaic components together, the overall power of the photovoltaic system loses its optimum power point.

Referring to fig. 8, based on mismatched monitoring pressures, it is necessary to establish reasonable monitoring and management mechanisms by which component-level target data can be extracted from component boards and fed back to owners or users. Real-time parameters such as voltage, current, arc, power and ambient temperature of the photovoltaic modules need to be monitored in time, and especially abnormal conditions such as power or faults of the modules need to be monitored in time, so that the monitoring data information can provide a basis for improving and optimizing each photovoltaic module, and the photovoltaic modules with power mismatch are reclassified into battery strings. Communication problems with photovoltaic module monitoring systems are involved whether attempts are made to achieve active control of the photovoltaic module by an external device or to send parameter information of the battery module locally to the external device. The intelligent management of the photovoltaic module comprises mismatch management, turn-off management, output power management and the like of the photovoltaic module besides the conventional working parameter monitoring.

With reference to fig. 8, in light of the foregoing, the core of the present application is to implement a method of addressing component mismatch and optimizing power generation in a photovoltaic power plant; in addition, the method for positioning and optimizing the series mismatch and the parallel mismatch of the components of the photovoltaic power station is achieved, and the method is the subject matter or subject matter of the application. The photovoltaic modules working on the left side of the maximum power point are classified, the photovoltaic modules working on the right side of the maximum power point are classified, the photovoltaic modules on the left side of the maximum power point are independently connected in series, the photovoltaic modules on the right side of the maximum power point are independently connected in series, the different groups are connected in series and in parallel, and the process is equivalent to the positioning and optimization of module series mismatch and module parallel mismatch. Such a positioning determines, for example, by the sign of the nature of the change in the output power of the photovoltaic module compared to the change in the output voltage of the upper photovoltaic module, that the photovoltaic module operates to the left or to the right of the maximum power point, such an optimization being, for example, that the photovoltaic modules on the left are connected in series individually, that the photovoltaic modules on the right are connected in series individually and that different strings are connected in parallel again. The positioning of course also includes finding the situation where the photovoltaic module happens to operate at the maximum power point position and the optimization, for example, also includes connecting the photovoltaic modules that happen to operate at the maximum power point in series and then in parallel individually.

While the above specification concludes with claims defining the preferred embodiments of the invention that are presented in conjunction with the specific embodiments disclosed, it is not intended to limit the invention to the specific embodiments disclosed. Various alterations and modifications will no doubt become apparent to those skilled in the art after having read the above description. Therefore, the appended claims should be construed to cover all such variations and modifications as fall within the true spirit and scope of the invention. Any and all equivalent ranges and contents within the scope of the claims should be considered to be within the intent and scope of the present invention.

Claims

1. A method for positioning and optimizing series mismatch and parallel mismatch of components of a photovoltaic power station is characterized by comprising the following steps of:

2. The method of claim 1, wherein:

and classifying and connecting the photovoltaic modules which just work at the maximum power point position in series to form a third type battery string, wherein the third type battery string is used for being connected with the first type battery string and the second type battery string in parallel.

3. The method of claim 1, wherein:

the sign of the property that the variation of the output power of the photovoltaic module is greater than the variation of the output voltage of the upper photovoltaic module determines whether the photovoltaic module operates on the left side or the right side of the maximum power point:

if the symbol is positive, the photovoltaic module works on the left side of the maximum power point;

if the sign is negative, the photovoltaic module works on the right side of the maximum power point.

4. The method of claim 3, wherein:

if the variation of the output power of the photovoltaic module is closer to zero than the variation of the output voltage of the upper photovoltaic module, the photovoltaic module just works at the maximum power point position.

5. The method of claim 1, wherein:

the inverter is supplied with power by at least the first-type battery pack string and the second-type battery pack string, the maximum power point of each photovoltaic module is dynamically analyzed in the process that the inverter carries out maximum power tracking, and secondary optimization is carried out:

6. The method of claim 5, wherein:

in the execution of the second optimization stage: and classifying the photovoltaic modules which just work at the position of the maximum power point in the first-class battery strings and the second-class battery strings into third-class battery strings, wherein the first-class battery strings are connected in parallel to the third-class battery strings.

7. The method of claim 1, wherein:

the device for connecting photovoltaic modules in series comprises:

the photovoltaic junction box is used for connecting the photovoltaic component to the battery string, the shutdown device is used for removing the photovoltaic component from the battery string or recovering the photovoltaic component in the removal state to be connected to the battery string, the power optimizer is used for setting the photovoltaic component at the maximum power point of the photovoltaic component, and the voltage converter is used for performing voltage conversion on the initial voltage of the photovoltaic component.

8. The method of claim 7, wherein:

the data acquisition module of the equipment configuration is used for acquiring the output power and the output voltage of the photovoltaic module and analyzing the variable quantity of the output power of the photovoltaic module and the variable quantity of the output voltage of the photovoltaic module.

9. A method for positioning and optimizing series mismatch and parallel mismatch of components of a photovoltaic power station is characterized by comprising the following steps:

analyzing the property sign of the variation of the output power of the photovoltaic module to the variation of the output voltage of the upper photovoltaic module;

connecting photovoltaic modules with signs of positive signs in series to form a battery pack string of one category;

connecting the photovoltaic modules with the negative signs in series to form battery string of another category;

so as to avoid generating power mismatch between photovoltaic modules with different maximum power point distributions when battery strings of different types are connected in parallel with each other.

10. The method of claim 9, wherein:

at least different types of battery pack strings supply power to the inverter, the maximum power point of each photovoltaic module is dynamically analyzed in the process that the inverter executes maximum power tracking, and secondary optimization is executed:

and in each battery string of different categories, the photovoltaic modules with the property signs changed into positive signs are classified into the battery string categories connected in series, and the photovoltaic modules with the property signs changed into negative signs are classified into the battery string categories connected in series.