Dynamic regulation method of fishery-solar complementary photovoltaic system based on string inverter

Abstract

The present invention provides a dynamic regulation method for a fishery-photovoltaic complementary system based on a string inverter, belonging to the field of smart grid and its control technology; the present invention groups a plurality of distributed photovoltaic components in parallel, combines the components with the same modal characteristics into a group, and performs adaptive filtering on photovoltaic components with different modalities, thereby greatly reducing the harmonic impact before large-scale photovoltaic grid connection, and can specifically process different harmonics, thereby improving the quality of grid-connected power; at the same time, by respectively analyzing the frequency spectrum characteristics of the output current and voltage of the photovoltaic strings in the group, determining the grid impedance compensation coefficient according to the harmonic frequency band range after secondary grouping, and finally calculating the grid connection standard through the total THD of the grid-connected current, the above two aspects of dynamic regulation are integrated to greatly improve the quality of photovoltaic grid-connected power.

Description

Technical Field

[0001] The present invention belongs to the technical field of smart grid and control thereof, and specifically relates to a dynamic regulation method for a fishery-photovoltaic complementary system based on a string inverter. Background Art

[0002] The string inverter is based on the concept of modularization. It takes the string as the unit, that is, each photovoltaic string in the photovoltaic module is input into a designated inverter, and multiple photovoltaic strings and inverters are modularly combined together, and all inverters are connected in parallel at the AC output end. Its main advantage is that it adopts a multi-channel MPPT (maximum power point tracking) solution, so it can track the maximum power point of each string. The application of string inverters in fish-light complementary photovoltaic power generation systems not only reduces system costs technically, but also enhances system reliability.

[0003] The inverter is not only the heart of the photovoltaic power station, but also the "eyes", "nose" and "ears" of the photovoltaic power station. It is responsible for converting the DC power of the photovoltaic modules into AC power and feeding it into the power grid, and is also responsible for feeding back its own faults and other information of the power station. If you do not have the basic judgment, analysis and troubleshooting capabilities for common faults, problems will easily occur. When multiple inverters are connected in parallel, the total harmonics are high. The THDI of a single inverter can be controlled to more than 2%, but if more than a certain number of inverters are connected in parallel, the total harmonics will be superimposed and difficult to suppress, and resonance is likely to occur. The total harmonics will be superimposed and difficult to suppress, and resonance is likely to occur. Summary of the invention

[0004] The purpose of the present invention is to solve the above-mentioned problems existing in the prior art and to provide a dynamic regulation method for a fish-photovoltaic complementary system based on a string inverter.

[0005] In a first aspect, the fishery-photovoltaic complementary system based on string inverter provided by the present invention comprises the following units: a plurality of distributed photovoltaic components, a string inverter, a voltage and current detector, a box transformer and a monitoring system.

[0006] Among them, multiple distributed photovoltaic components are connected to the grid through string inverters and voltage and current detectors via box transformers. The peripherals connected to the voltage and current detection also include electricity meters, environmental monitoring and centralized monitoring centers. The string inverters are output to the grid through filter components and box transformers.

[0007] Furthermore, the present invention provides a dynamic adjustment method based on the above-mentioned fish-solar complementary photovoltaic system, which specifically comprises the following steps:

[0008] Step 1: Group multiple distributed photovoltaic modules in parallel, design the grouping according to the location of the photovoltaic modules, the rated operating voltage (V) range and the power capacity (W) parameters, and divide the photovoltaic modules in a certain area and the voltage and power capacity into a group for parallel connection;

[0009] Step 2: Analyze the spectral characteristics of the output current and voltage of the photovoltaic strings in the group, calculate the intensity and phase distribution of the current and low voltage at various frequencies, the resonance point O and the harmonic content, where O is XHZ and the harmonic content P%, cascade and normalize the results obtained by the above calculations to form the modal characteristics of the photovoltaic strings in the group , where i is the grouping category;

[0010] Step 3: Perform modal division based on the modal feature F obtained in step 3, and divide the photovoltaic modules in the same mode into secondary groups. The specific modal division includes:

[0011] (1) Constructing modal features The feature space contains n sample points, , initially determine a center point C(t);

[0012] (2) Calculate all points in the circular space with a set radius of R The vector with the center point C;

[0013] (3) Calculate the average value of the modal characteristics of all photovoltaic strings in the entire circular space to obtain an offset vector ; , where function G is the classification kernel function, C is the initial center point feature vector, and h is the step size;

[0014] (4) Move the center point center to the offset mean position, C(t+1) = +C(t), t is the number of iterations;

[0015] (5) Repeat steps (1) to (4) until a certain condition is met. The end condition includes that the number of iterations reaches a preset number or the offset position does not change.

[0016] (6) The photovoltaic modules in the same mode are divided into two groups according to the final center position.

[0017] Step 4, filtering out harmonics of the photovoltaic components in the same mode in step 3 by adaptively selecting a filter component;

[0018] Specifically, a corresponding suitable filter is selected from a filter component including various types of filters based on the harmonic mode. In the present invention, the filter at least includes a passive filter and an active filter, and the passive filter includes an RLC filter with various parameter configurations.

[0019] Step 5, according to the grid impedance compensation coefficient determined by the harmonic frequency band after secondary grouping, the corresponding grid-connected current feedforward differential coefficient is calculated according to the grid impedance value, and the differential coefficient of the grid-connected current feedforward link is calculated and compensated according to the corresponding grid reactance;

[0020] Specifically, the harmonic frequency band range after secondary grouping is divided into k frequency band intervals , then the grid reactance values ​​corresponding to the resonance points falling into the above frequency bands are Lk, and the grid current feedforward differential coefficient is calculated according to the grid impedance ;

[0021] in, , where the maximum value of the compensation coefficient is set to , is the phase angle change of the harmonic frequency relative to the minimum frequency point, is the maximum value of phase angle change.

[0022] Step 6, determine whether the total THD of the grid-connected current after filtering and compensation meets the grid-connected standard. If it meets the grid-connected standard, the grid is connected to the grid through the box transformer for grid-connected power output. Specifically, if the total THD of the grid-connected current is less than the preset threshold T, it is determined to meet the grid-connected standard.

[0023] Compared with the prior art, the beneficial effects of the present invention are as follows: the present invention groups multiple distributed photovoltaic components in parallel, combines the components with the same modal characteristics into one group, and performs adaptive filtering on photovoltaic components with different modalities, which can greatly reduce the harmonic impact before large-scale photovoltaic grid connection, and can specifically handle different harmonics, thereby improving the power quality of grid connection; at the same time, by performing spectral characteristic analysis on the output current and voltage of the photovoltaic strings in the group, determining the grid impedance compensation coefficient according to the harmonic frequency band range after secondary grouping, and finally calculating the grid connection standard through the total THD of the grid-connected current, the above two aspects are integrated for dynamic adjustment to greatly improve the power quality of photovoltaic grid connection. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is the structural diagram of the fishery-photovoltaic complementary system based on string inverters for this application;

[0025] Figure 2 This is a flow chart of the application method. DETAILED DESCRIPTION

[0026] The present invention is further described in detail below in conjunction with the accompanying drawings:

[0027] Example 1, see attached Figure 1The fishery-photovoltaic complementary system based on string inverter provided by the present invention comprises the following units: a plurality of distributed photovoltaic components, a string inverter, a voltage and current detector, a box transformer and a monitoring system.

[0028] Among them, multiple distributed photovoltaic components are connected to the grid through string inverters and voltage and current detectors via box transformers. The peripherals connected to the voltage and current detection also include electricity meters, environmental monitoring and centralized monitoring centers. The string inverters are output to the grid through filter components and box transformers.

[0029] Example 2, see the attached specification Figure 2 Based on the above-mentioned fish-light complementary photovoltaic system, a dynamic adjustment method is provided, which specifically includes the following steps:

[0030] Step 1: Group multiple distributed photovoltaic modules in parallel, design the grouping according to the location of the photovoltaic modules, the rated operating voltage (V) range and the power capacity (W) parameters, and divide the photovoltaic modules in a certain area and the voltage and power capacity into a group for parallel connection;

[0031] Step 2: Analyze the spectral characteristics of the output current and voltage of the photovoltaic strings in the group, calculate the intensity and phase distribution of the current and low voltage at various frequencies, the resonance point O and the harmonic content, where O is XHZ and the harmonic content P%, cascade and normalize the results obtained by the above calculations to form the modal characteristics of the photovoltaic strings in the group , where i is the grouping category;

[0032] Step 3: Perform modal division based on the modal feature F obtained in step 3, and divide the photovoltaic modules in the same mode into secondary groups. The specific modal division includes:

[0033] (1) Constructing modal features The feature space contains n sample points, , initially determine a center point C(t);

[0034] (2) Calculate all points in the circular space with a set radius of R The vector with the center point C;

[0035] (3) Calculate the average value of the modal characteristics of all photovoltaic strings in the entire circular space to obtain an offset vector ; , where function G is the classification kernel function, C is the initial center point feature vector, and h is the step size;

[0036] (4) Move the center point center to the offset mean position, C(t+1) = +C(t), t is the number of iterations;

[0037] (5) Repeat steps (1) to (4) until a certain condition is met. The end condition includes that the number of iterations reaches a preset number or the offset position does not change.

[0038] (6) The photovoltaic modules in the same mode are divided into two groups according to the final center position.

[0039] Step 4, filtering out harmonics of the photovoltaic components in the same mode in step 3 by adaptively selecting a filter component;

[0040] Specifically, a corresponding suitable filter is selected from a filter component including various types of filters based on the harmonic mode. In the present invention, the filter at least includes a passive filter and an active filter, and the passive filter includes an RLC filter with various parameter configurations.

[0041] Step 5, according to the grid impedance compensation coefficient determined by the harmonic frequency band after secondary grouping, the corresponding grid-connected current feedforward differential coefficient is calculated according to the grid impedance value, and the differential coefficient of the grid-connected current feedforward link is calculated and compensated according to the corresponding grid reactance;

[0042] Specifically, the harmonic frequency band range after secondary grouping is divided into k frequency band intervals , then the grid reactance values ​​corresponding to the resonance points falling into the above frequency bands are Lk, and the grid current feedforward differential coefficient is calculated according to the grid impedance ;

[0043] in, , where the maximum value of the compensation coefficient is set to , is the phase angle change of the harmonic frequency relative to the minimum frequency point, is the maximum value of phase angle change.

[0044] Step 6, determine whether the total THD of the grid-connected current after filtering and compensation meets the grid-connected standard. If it meets the grid-connected standard, the grid is connected to the grid through the box transformer for grid-connected power output. Specifically, if the total THD of the grid-connected current is less than the preset threshold T, it is determined to meet the grid-connected standard.

[0045] Some embodiments of the present application further provide a computer-readable storage medium having a computer program stored thereon. When the computer program is executed by a processor, the system functions described in the method embodiments are executed.

[0046] Some embodiments of the present application also provide an electronic device, characterized in that it includes a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the system execution method can be implemented when the processor executes the program.

[0047] The above are only embodiments of the present application and are not intended to limit the scope of protection of the present application. For those skilled in the art, the present application may have various changes and variations. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present application should be included in the scope of protection of the present application. It should be noted that similar reference numerals and letters represent similar items in the following drawings, so once an item is defined in one drawing, it does not need to be further defined and explained in the subsequent drawings.

[0048] The above are only specific implementations of the present application, but the protection scope of the present application is not limited thereto. Any technician familiar with the technical field can easily think of changes or substitutions within the technical scope disclosed in the present application, which should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

[0049] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprise a ..." do not exclude the existence of other identical elements in the process, method, article or device including the elements.

[0050] In the description of the present invention, unless otherwise specified, the terms "upper", "lower", "left", "right", "inside", "outside", etc. indicate directions or positional relationships based on the directions or positional relationships shown in the accompanying drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction. Therefore, they cannot be understood as limitations on the present invention.

[0051] Finally, it should be explained that the above technical solution is only one implementation method of the present invention. For those skilled in the art, it is easy to make various types of improvements or modifications based on the application methods and principles disclosed in the present invention, and it is not limited to the method described in the above specific implementation method of the present invention. Therefore, the method described above is only preferred and does not have a restrictive meaning.

Claims

1. A dynamic mediation method for a photovoltaic system based on a string inverter: wherein the photovoltaic system comprises a plurality of distributed photovoltaic components, a string inverter, a voltage and current detector, a box transformer and a monitoring system; wherein the plurality of distributed photovoltaic components are connected to the power grid via a box transformer through a string inverter and a voltage and current detector, and the peripherals connected to the voltage and current detection also include an electric meter, an environmental monitoring and a centralized monitoring center, and the string inverter is output to the power grid via a filter component and a box transformer; the specific mediation method performs the following steps: Step 1, grouping multiple distributed photovoltaic components in parallel; Step 2: Analyze the spectral characteristics of the output current and voltage of the photovoltaic strings in the group respectively; calculate the intensity and phase distribution of the current and low voltage at various frequencies, the resonance point O and the harmonic content, where O is XHZ and the harmonic content P%, cascade and normalize the results obtained by the above calculations to form the modal characteristics of the photovoltaic strings in the group , where i is the grouping category; Step 3: Based on the modal features obtained in step 2 Perform modal division and divide photovoltaic modules in the same mode into secondary groups; Step 4, filtering out harmonics of the photovoltaic components in the same mode in step 3 by adaptively selecting a filter component; Step 5: The grid impedance compensation coefficient is determined according to the harmonic frequency band range after secondary grouping, and the corresponding grid-connected current feedforward differential coefficient is calculated according to the grid impedance value. The differential coefficient of the grid-connected current feedforward link is calculated and compensated according to the corresponding grid reactance; the harmonic frequency band range after secondary grouping is divided into k frequency band intervals , then the grid reactance values ​​corresponding to the resonance points falling into the above frequency bands are Lk, and the grid current feedforward differential coefficient is calculated according to the grid impedance ; in, , where the maximum value of the compensation coefficient is set to , is the phase angle change of the harmonic frequency relative to the minimum frequency point, is the maximum value of phase angle change; Step 6, determine whether the total THD of the grid-connected current after filtering and compensation meets the grid-connected standard. If it meets the grid-connected standard, connect the grid through the box-type transformer to the grid for grid-connected power output.

2. The method according to claim 1, characterized in that In step 1, the photovoltaic modules are grouped and designed according to their locations, rated operating voltage ranges, and power capacity parameters, and the photovoltaic modules within a certain area and with different voltages and power capacities are divided into a group for parallel connection.

3. The method according to claim 2, characterized in that: In step 3, the specific modal division includes: (a) Constructing modal features The feature space contains n sample points, , initially determine a center point C(t); (b) Calculate all points in the circular space with a set radius of R The vector with the center point C; (c) Calculate the average value of the modal characteristics of all photovoltaic strings in the entire circular space to obtain an offset vector ; , where function G is the classification kernel function, C is the initial center point feature vector, and h is the step size; (d) Move the center point center to the offset mean position, C(t+1) = +C(t), t is the number of iterations; (e) Repeat steps (a) to (d) until a certain condition is met, where the end condition includes that the number of iterations reaches a preset number or the offset position does not change; (f) The PV modules in the same mode are divided into two groups according to their final center positions.

4. The method according to claim 3, characterized in that: Step 4, filtering out harmonics of the photovoltaic components in the same mode in step 3 by adaptively selecting a filter component; A corresponding filter is selected from a filter component including multiple types of filters based on the harmonic mode. The filter includes at least a passive filter and an active filter. The passive filter includes an RLC filter with multiple parameter configurations.

5. The method according to claim 4, characterized in that In step 6, if the total THD of the grid-connected current is less than the preset threshold value T, it is determined to meet the grid-connected standard.

6. An electronic device, characterized in that: The invention comprises a memory, a processor and a computer program stored in the memory and executable on the processor, wherein the processor can implement the mediation method described in any one of claims 1 to 5 when executing the program.

7. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores a computer program, wherein the program, when executed by a processor, can implement the mediation method described in any one of claims 1 to 5.

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