An optimization control method, device and system for DC microgrid

Abstract

The present application relates to the technical field of electric energy storage systems, and specifically to an optimization control method, device and system for a DC microgrid, the method comprising: collecting the control voltage, output voltage and output power of a photovoltaic battery group; determining an output characteristic sequence and determining an output characteristic weight; determining an upper limit and a lower limit of a search voltage of a photovoltaic cell, determining an optimal search voltage of the photovoltaic battery group, and determining an optimal search step size at the current acquisition moment; obtaining a control voltage at the next acquisition moment of the current acquisition moment based on the optimal search step size, output power and control voltage at the current acquisition moment, and a basic search step size of the photovoltaic cell, and realizing optimization control for a DC microgrid based on the control voltage at the next acquisition moment of the current acquisition moment. The present application solves the problem that the multi-peak phenomenon of the power-voltage curve of a photovoltaic battery group easily causes a DC microgrid to be unable to maintain maximum power generation.

Description

Technical Field

[0001] The present application relates to the technical field of electric energy storage systems, and in particular to an optimization control method, device and system for a direct current microgrid. Background Art

[0002] A DC microgrid is a form of grid that directly uses the DC power generated by new energy power generation equipment such as photovoltaic battery groups to achieve local power supply, and relies on the power supply of new energy equipment such as photovoltaic battery groups. In order to keep the DC microgrid generating power at the maximum power and maximize the output power of the photovoltaic battery group, it is necessary to use the maximum power point tracking MPPT technology to adjust the output voltage of the photovoltaic battery group. Specifically, the MPPT technology uses an intelligent optimization algorithm to continuously adjust the output voltage of the photovoltaic battery group to find the output voltage corresponding to the maximum power, ensuring that the photovoltaic battery group and the DC microgrid are powered at the maximum power.

[0003] The photovoltaic battery group is composed of multiple photovoltaic cells. The power-voltage curve of each photovoltaic cell in the photovoltaic battery group is a single-peak curve. The intelligent optimization algorithm can easily find the maximum power position in the single-peak curve. However, the superposition curve obtained by superimposing the power-voltage curves of multiple photovoltaic cells constituting the photovoltaic battery group often has a multi-peak phenomenon. When using the intelligent optimization algorithm to find the maximum power position in the superposition curve, it is often affected by the multi-peak phenomenon. Specifically, when the search step size of the intelligent optimization algorithm is too short, the maximum power position determined by the intelligent optimization algorithm is prone to fall into the problem of local optimal solution; when the search step size of the intelligent optimization algorithm is too long, the process of determining the maximum power position by the intelligent optimization algorithm is prone to affect the stability of the DC microgrid power supply. Therefore, in the process of realizing the stability control of the DC microgrid, it is easy for the DC microgrid to fail to maintain the maximum power generation due to the multi-peak phenomenon of the superposition curve of the photovoltaic battery group. Summary of the invention

[0004] In order to solve the above technical problems, the purpose of this application is to provide an optimization control method, device and system for a DC microgrid. The technical solutions adopted are as follows:

[0005] In a first aspect, an embodiment of the present application provides an optimization control method for a DC microgrid, the method comprising the following steps:

[0006] Collecting the control voltage of the photovoltaic battery group at the current collection time and the output voltage and output power of each photovoltaic battery in the photovoltaic battery group at the current collection time and at different collection times in the previous local time period;

[0007] According to the output voltage and output power of the photovoltaic cell at the same collection time, the number pairs at the same collection time are determined; according to the number pairs of the photovoltaic cell at all collection times, the output characteristic sequence of the photovoltaic cell is determined; according to the similarity between the output characteristic sequence of the photovoltaic cell and the output characteristic sequences of all other photovoltaic cells, the output characteristic weight of the photovoltaic cell is determined;

[0008] According to the preset basic search step of the photovoltaic cell, the positive and negative slope values ​​contained in the output characteristic sequence of the photovoltaic cell, and the output voltage of the number pair corresponding to the slope contained in the output characteristic sequence, the search voltage upper limit and the search voltage lower limit of the photovoltaic cell are determined; according to the output characteristic weights of all photovoltaic cells contained in the photovoltaic cell group, the search voltage upper limit and the search voltage lower limit, the optimal search voltage of the photovoltaic cell group is determined; according to the optimal search voltage of the photovoltaic cell group and the control voltage of the photovoltaic cell group at the current collection time, the optimal search step at the current collection time is determined;

[0009] According to the optimal search step, output power and control voltage at the current collection moment, and the basic search step of the photovoltaic cell, the control voltage at the next collection moment of the current collection moment is obtained, and according to the control voltage at the next collection moment of the current collection moment, the stability of the DC microgrid is intelligently controlled.

[0010] Further, the output voltage and output power of the photovoltaic cell at the same collection time are used to determine the number of pairs at the same collection time, and the output characteristic sequence of the photovoltaic cell is determined according to the number of pairs of the photovoltaic cell at all collection times. The specific process of obtaining is:

[0011] The number of pairs consisting of the output voltage and output power of the photovoltaic cell at the same collection time is recorded as the number of pairs of the photovoltaic cell at the same collection time, the number of pairs with the same output voltage of the photovoltaic cell at all collection times is selected, the average value of the output power of the selected number of pairs and the output voltage are used to form a new number pair, and the new number pair is used to replace the number pair with the same output voltage;

[0012] Using the output voltage as the horizontal axis and the output power as the vertical axis, marking all number pairs of any photovoltaic cell in a plane rectangular coordinate system, and obtaining an output voltage-output power number pair graph of any photovoltaic cell;

[0013] In the output voltage-output power pair diagram, points in the output voltage-output power pair diagram are selected in the order of output voltage from small to large, and the points in the output voltage-output power pair diagram are marked with natural numbers starting from 1 in the order of selection; starting from the point with sequence number 2, each point is recorded as a target point, and the slope between the target point and the point with a sequence number less than 1 than the target point is recorded as the slope of the target point; the slopes of all points are arranged in the order of the sequence numbers of the points from small to large, and the output characteristic sequence of the photovoltaic cell is obtained.

[0014] Furthermore, the process of constructing the output characteristic weight of the photovoltaic cell is as follows:

[0015] The cosine similarity between the output characteristic sequences of two different photovoltaic cells is recorded as the first output characteristic weights of the two different photovoltaic cells, the average of the first output characteristic weights of any photovoltaic cell and all other photovoltaic cells is recorded as the second output characteristic weight of any photovoltaic cell, and the normalized value of the second output characteristic weight of any photovoltaic cell is recorded as the output characteristic weight of any photovoltaic cell.

[0016] Further, the search voltage upper limit and the search voltage lower limit of the photovoltaic cell are determined according to the preset basic search step length of the photovoltaic cell, the positive and negative values ​​of the slope values ​​contained in the output characteristic sequence of the photovoltaic cell, and the output voltage of the number pair corresponding to the slope contained in the output characteristic sequence. The specific process of obtaining is:

[0017] There are three possible situations in the output characteristic sequence of photovoltaic cells: the slopes of the points contained in the output characteristic sequence of photovoltaic cells are all positive, all negative, or both positive and negative;

[0018] According to three possible situations of the output characteristic sequence of the photovoltaic cell, the search voltage upper limit and the search voltage lower limit of the photovoltaic cell are determined respectively.

[0019] Furthermore, the specific process of determining the upper limit and the lower limit of the search voltage of the photovoltaic cell respectively according to the three possible situations of the output characteristic sequence of the photovoltaic cell is as follows:

[0020] When the slopes of the points contained in the output characteristic sequence of the photovoltaic cell are all positive values: the maximum value of the output voltages of the two number pairs corresponding to the last slope in the output characteristic sequence of the photovoltaic cell is recorded as the search voltage lower limit, and the sum of the search voltage lower limit and the basic search step length is recorded as the search voltage upper limit;

[0021] When the slope of the points included in the output characteristic sequence of the photovoltaic cell contains both positive and negative values: select the last positive slope included in the output characteristic sequence of the photovoltaic cell, record the maximum value of the output voltage of the two number pairs corresponding to the selected slope as the search voltage lower limit, select the first negative slope included in the output characteristic sequence of the photovoltaic cell, record the minimum value of the output voltage of the two number pairs corresponding to the selected slope as the search voltage upper limit;

[0022] When the slopes of the points included in the output characteristic sequence of the photovoltaic cell are all negative values: select the first slope included in the output characteristic sequence of the photovoltaic cell, record the minimum value of the output voltage of the two number pairs corresponding to the selected slope as the search voltage upper limit, and record the difference between the search voltage upper limit and the basic search step as the search voltage lower limit.

[0023] Furthermore, the specific process of determining the optimal search voltage of the photovoltaic battery group according to the output characteristic weights of all photovoltaic batteries included in the photovoltaic battery group, the search voltage upper limit and the search voltage lower limit is as follows:

[0024] The output characteristic weight of the photovoltaic cell is used as the weight of the search voltage upper limit of the photovoltaic cell, and the search voltage upper limits of all photovoltaic cells included in the photovoltaic cell group are weighted and summed to obtain the optimal search voltage upper limit of the photovoltaic cell group;

[0025] The output characteristic weight of the photovoltaic cell is used as the weight of the search voltage lower limit of the photovoltaic cell, and the search voltage lower limits of all photovoltaic cells included in the photovoltaic cell group are weighted and summed to obtain the optimal search voltage lower limit of the photovoltaic cell group;

[0026] The average of the upper limit of the optimal search voltage and the lower limit of the optimal search voltage of the photovoltaic battery group is recorded as the optimal search voltage of the photovoltaic battery group.

[0027] Further, the optimal search step length at the current acquisition moment is determined according to the optimal search voltage of the photovoltaic battery group and the control voltage of the photovoltaic battery group at the current acquisition moment. The specific process of obtaining is:

[0028] The absolute value of the difference between the optimal search voltage of the photovoltaic battery group and the control voltage of the photovoltaic battery group at the current acquisition time is recorded as the optimal search step length at the current acquisition time.

[0029] Further, the control voltage at the next acquisition moment of the current acquisition moment is obtained according to the optimal search step size, output power and control voltage at the current acquisition moment, and the basic search step size of the photovoltaic cell, and the stability intelligent control of the DC microgrid is realized according to the control voltage at the next acquisition moment of the current acquisition moment. The specific process of obtaining is:

[0030] The twice of the basic search step of the photovoltaic cell is taken as the upper limit of the search step of the intelligent optimization algorithm, the ratio of the optimal search step at the current acquisition time to the upper limit of the search step is recorded as the first ratio at the current acquisition time, and the product of the first ratio at the current acquisition time and the preset maximum learning rate is recorded as the dynamic learning rate at the current acquisition time;

[0031] The output power at the current acquisition moment is taken as the objective function, the control voltage at the current acquisition moment is taken as the independent variable, the dynamic learning rate at the current acquisition moment is taken as the learning rate, and the intelligent optimization algorithm is used to obtain the control voltage at the next acquisition moment of the current acquisition moment;

[0032] At the next collection moment of the current collection moment, the internal resistance of the photovoltaic battery group is adjusted so that the control voltage at the next collection moment of the current collection moment is equal to the control voltage at the next collection moment of the current collection moment obtained using the intelligent optimization algorithm, thereby realizing intelligent control of the stability of the DC microgrid.

[0033] In a second aspect, an embodiment of the present application provides an optimization control device for a DC microgrid, the optimization control device comprising: a power grid photovoltaic data acquisition module, a photovoltaic output characteristic analysis module, a control voltage search step determination module, and a DC microgrid control module.

[0034] The power grid photovoltaic data acquisition module is used to collect the control voltage of the photovoltaic battery group at the current acquisition time and the output voltage and output power of each photovoltaic cell in the photovoltaic battery group at the current acquisition time and at different acquisition times in the previous local time period;

[0035] The photovoltaic output characteristic analysis module is used to determine the number pairs at the same collection time according to the output voltage and output power of the photovoltaic cell at the same collection time, determine the output characteristic sequence of the photovoltaic cell according to the number pairs of the photovoltaic cell at all collection times, and determine the output characteristic weight of the photovoltaic cell according to the similarity between the output characteristic sequence of the photovoltaic cell and the output characteristic sequences of all other photovoltaic cells;

[0036] A control voltage search step determination module is used to determine the search voltage upper limit and the search voltage lower limit of the photovoltaic cell according to the preset basic search step of the photovoltaic cell, the positive and negative values ​​of the slope values ​​contained in the output characteristic sequence of the photovoltaic cell, and the output voltage of the number pair corresponding to the slope contained in the output characteristic sequence, determine the optimal search voltage of the photovoltaic cell group according to the output characteristic weights of all photovoltaic cells contained in the photovoltaic cell group, the search voltage upper limit and the search voltage lower limit, and determine the optimal search step at the current acquisition time according to the optimal search voltage of the photovoltaic cell group and the control voltage of the photovoltaic cell group at the current acquisition time;

[0037] The DC microgrid control module is used to obtain the control voltage at the next collection moment of the current collection moment according to the optimal search step, output power and control voltage at the current collection moment, as well as the basic search step of the photovoltaic cell, and realize intelligent control of the stability of the DC microgrid according to the control voltage at the next collection moment of the current collection moment.

[0038] In a third aspect, an embodiment of the present application further provides an optimization control system for a DC microgrid, the system comprising a memory, a processor, and a computer program stored in the memory and running on the processor, wherein the processor implements the steps of any one of the above methods when executing the computer program.

[0039] It can be seen from the above embodiments that the optimization control method, device and system for a DC microgrid provided in the embodiments of the present application have at least the following beneficial effects:

[0040] The present application uses the output voltage and output power of the photovoltaic cell at each of the same collection moments in all collection moments to represent the output characteristics of the photovoltaic cell, and assigns similar output characteristic weights to photovoltaic cells with similar output characteristics. Further, the search voltage upper limit, search voltage lower limit and optimal search voltage of the photovoltaic cell are determined. The search voltage upper limit, search voltage lower limit and optimal search voltage correspond to the maximum value, minimum value and optimal value of the search step value in the process of determining the control voltage, respectively. Among them, the optimal search voltage is determined on the basis of considering the output characteristic weights of different photovoltaic cells in the photovoltaic cell group, which can simultaneously ensure that the output voltage of the photovoltaic cell group is near the optimal operating voltage of different photovoltaic cells, and keep the DC microgrid at maximum power generation. Power generation, providing stable and sufficient electricity, avoiding the control voltage of the DC microgrid from falling into the local optimal solution; then, determining the optimal search step size at the current acquisition time, ensuring that the search step size is reasonable, effectively avoiding the output power fluctuation caused by frequent adjustment of the control voltage, making the control effect of the DC microgrid more stable, and solving the problem that the multi-peak phenomenon of the power-voltage curve of the photovoltaic battery group easily leads to the inability of the DC microgrid to maintain the maximum power generation; finally, obtaining the control voltage at the next acquisition time of the current acquisition time, and realizing the intelligent control of the stability of the DC microgrid according to the control voltage at the next acquisition time of the current acquisition time, maintaining the DC microgrid to generate electricity at the maximum power, and improving the stability of the control effect of the DC microgrid. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] In order to more clearly illustrate the technical solutions and advantages in the embodiments of the present application or the prior art, the drawings required for use in the embodiments or the prior art descriptions are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0042] Figure 1 A flowchart of a method for optimizing control of a DC microgrid provided in accordance with an embodiment of the present application;

[0043] Figure 2 A schematic diagram of output voltage and output power provided for one embodiment of the present application;

[0044] Figure 3 A schematic diagram of an output voltage-output power pair diagram provided for one embodiment of the present application;

[0045] Figure 4 A flow chart for obtaining output characteristic weights provided in one embodiment of the present application;

[0046] Figure 5 A schematic structural diagram of an optimization control device for a DC microgrid provided in accordance with an embodiment of the present application. DETAILED DESCRIPTION

[0047] In order to further explain the technical means and effects adopted by the present application to achieve the predetermined invention purpose, the following is a detailed description of the optimization control method, device and system for a DC microgrid proposed in accordance with the present application, its specific implementation method, structure, features and effects, in combination with the accompanying drawings and preferred embodiments. In the following description, different "one embodiment" or "another embodiment" does not necessarily refer to the same embodiment. In addition, specific features, structures or characteristics in one or more embodiments may be combined in any suitable form.

[0048] The following is a detailed description of a specific scheme of an optimization control method, device and system for a DC microgrid provided by the present application in conjunction with the accompanying drawings.

[0049] See also Figure 1 , which shows a flowchart of a method for optimizing control of a DC microgrid provided by an embodiment of the present application, the method comprising the following steps:

[0050] S001: Collecting the control voltage of the photovoltaic battery group at the current collection time and the output voltage and output power of each photovoltaic cell in the photovoltaic battery group at the current collection time and at different collection times in the previous local time period.

[0051] The control voltage of the photovoltaic battery group at the current collection time is collected using a Hall sensor. The output voltage and output power of each photovoltaic cell in the photovoltaic battery group at the current collection time and at different previous collection times are collected using a Hall sensor.

[0052] Preferably, in one embodiment of the present application, the interval of collecting the output voltage and output power of each photovoltaic cell is 100 milliseconds, and the number of continuously collected output voltages and output powers is 50. In actual application, as other implementation methods, the implementer can determine the interval of collecting the output voltage and output power and the number of samples according to actual conditions, and the present application does not impose any special restrictions.

[0053] It is understandable that for each photovoltaic cell in the photovoltaic cell group, there is a corresponding output voltage and output power at each collection moment. In particular, different photovoltaic cells in the photovoltaic cell group are usually connected in parallel, so the output voltages of different photovoltaic cells collected at the same collection moment are the same.

[0054] At this point, the control voltage of the photovoltaic battery group at the current collection time and the output voltage and output power of each photovoltaic cell in the photovoltaic battery group at the current collection time and at different collection times in the previous local time period are obtained. The output voltage and output power diagram is shown in Figure 2 As shown. Figure 2 In the figure, the horizontal axis is the sampling time, the sampling time is marked from 0, the time interval between every two adjacent sampling times with a difference of 1 is 100 milliseconds, and the vertical axis is the sampling value of the output voltage and the output power, the unit of the output voltage is volt, and the unit of the output power is watt.

[0055] S002: Determine the number pairs at the same collection time according to the output voltage and output power of the photovoltaic cell at the same collection time, determine the output characteristic sequence of the photovoltaic cell according to the number pairs of the photovoltaic cell at all collection times, and determine the output characteristic weight of the photovoltaic cell according to the similarity between the output characteristic sequence of the photovoltaic cell and the output characteristic sequences of all other photovoltaic cells.

[0056] The output characteristics of a photovoltaic cell refer to the changing pattern between the output power and output voltage of the photovoltaic cell. Usually, the output voltage is used as the independent variable and the output power is used as the dependent variable. An output voltage-output power curve is established in a plane rectangular coordinate system. The output voltage-output power curve is used to measure the output characteristics of the photovoltaic cell.

[0057] The output characteristics of photovoltaic cells are related to the hardware composition of photovoltaic cells and the environment in which they are located. When the environment in which photovoltaic cells are located changes, the output characteristics of photovoltaic cells will also change accordingly. Among them, the factors affecting the environment in which photovoltaic cells are located mainly include light intensity and temperature. Since the impact of the environment in which photovoltaic cells are located on the output characteristics of photovoltaic cells cannot be directly measured, and the changes in the output characteristics of photovoltaic cells cannot be directly determined by changes in the environment in which photovoltaic cells are located, the output voltage of the photovoltaic battery group is generally adjusted in real time to ensure that the output voltage of the photovoltaic battery group is close to the optimal operating voltage of different photovoltaic cells, so that the output power of the photovoltaic battery group is kept at the maximum, thereby maintaining the DC microgrid to generate electricity at the maximum power and provide stable and sufficient electricity.

[0058] In order to measure the output characteristics of photovoltaic cells, each photovoltaic cell is analyzed separately, and the number pairs consisting of the output voltage and output power of the photovoltaic cell at the same collection time are recorded as the number pairs of the photovoltaic cell at the same collection time. The output voltages of the photovoltaic cell pairs at all collection times are compared, and the number pairs with the same output voltage are selected. The average value of the output power of the selected number pairs and the output voltage form a new number pair, and the new number pairs are used to replace the number pairs with the same output voltage. With the output voltage as the horizontal axis and the output power as the vertical axis, all the number pairs of any photovoltaic cell are marked in the plane rectangular coordinate system to obtain the output voltage-output power number pair graph of any photovoltaic cell.

[0059] The output voltage-output power ratio diagram is as follows: Figure 3 As shown, in Figure 3 In the graph, the horizontal axis is the output voltage, the unit of the output voltage is volt, and the vertical axis is the output power, the unit of the output power is watt. Figure 3 The number of corresponding pairs of points in .

[0060] In the output voltage-output power pair diagram, select points in the output voltage-output power pair diagram in the order of output voltage from small to large, and mark the points in the output voltage-output power pair diagram with natural numbers starting from 1 in the order of selection. Starting from the point with sequence number 2, each point is recorded as a target point, and the slope between the target point and the point with a sequence number 1 less than the sequence number of the target point is recorded as the slope of the target point. Arrange the slopes of all points in the order of the sequence numbers of the points from small to large to obtain the output characteristic sequence of the photovoltaic cell.

[0061] It can be understood that for each photovoltaic cell in the photovoltaic cell group, there is a corresponding output voltage-output power pair diagram and a corresponding output characteristic sequence.

[0062] The slope of the target point is the relationship between the output voltage and the output power at the acquisition time corresponding to the target point. When the slope of the target point is larger, the trend of the output power of the photovoltaic cell increasing with the increase of the output voltage at the acquisition time corresponding to the target point is more obvious. The output characteristic sequence of the photovoltaic cell uses the relationship between the output voltage and the output power of the photovoltaic cell at different output voltages to characterize the output characteristics of the photovoltaic cell.

[0063] In order to keep the DC microgrid generating electricity at maximum power and provide stable and sufficient electricity, it is necessary to ensure that the output voltage of the photovoltaic battery group is close to the optimal operating voltage of different photovoltaic cells. Therefore, in the process of determining the control voltage of the DC microgrid, it is necessary to assign similar weights to photovoltaic cells with similar output characteristics to ensure the overall regulation of the photovoltaic battery group and avoid the determination of the control voltage of the DC microgrid falling into a local optimal solution.

[0064] The output characteristic weight of the photovoltaic cell is determined based on the similarity between the output characteristic sequence of the photovoltaic cell and the output characteristic sequences of all other photovoltaic cells. The output characteristic weight acquisition flow chart is as follows: Figure 4 shown.

[0065] Preferably, as an embodiment of the present application, the cosine similarity between the output characteristic sequences of two different photovoltaic cells is recorded as the first output characteristic weights of the two different photovoltaic cells, the average of the first output characteristic weights of any photovoltaic cell and all other photovoltaic cells is recorded as the second output characteristic weight of any photovoltaic cell, and the normalized value of the second output characteristic weight of any photovoltaic cell is recorded as the output characteristic weight of any photovoltaic cell.

[0066] Among them, this embodiment selects cosine similarity as the similarity measure between output characteristic sequences. The implementer can use other methods in the prior art such as Pearson correlation coefficient to measure the similarity between output characteristic sequences, and this application does not impose any special restrictions.

[0067] The specific method for normalizing the second output characteristic weight of the photovoltaic cell in this embodiment is: the cumulative sum of the second output characteristic weights of all photovoltaic cells is recorded as the third output characteristic weight, and the ratio of the second output characteristic weight to the third output characteristic weight of any photovoltaic cell is recorded as the output characteristic weight of the any photovoltaic cell.

[0068] When the similarity between the output characteristic sequences of a photovoltaic cell and all other photovoltaic cells is greater, the weight of the output characteristic of the photovoltaic cell is greater. At this time, the output characteristics of the photovoltaic cell and other photovoltaic cells are more similar. In the process of determining the control voltage of the DC microgrid, the output characteristics of the photovoltaic cell should be given more attention to avoid the determination of the control voltage of the DC microgrid falling into a local optimal solution.

[0069] At this point, the output characteristic weights of the photovoltaic cells are determined.

[0070] S003: Determine the search voltage upper limit and search voltage lower limit of the photovoltaic cell according to the preset basic search step of the photovoltaic cell, the positive and negative values ​​of the slope contained in the output characteristic sequence of the photovoltaic cell, and the output voltage of the number pairs corresponding to the slope contained in the output characteristic sequence; determine the optimal search voltage of the photovoltaic cell group according to the output characteristic weights of all photovoltaic cells contained in the photovoltaic cell group, the search voltage upper limit and the search voltage lower limit; determine the optimal search step at the current acquisition moment according to the optimal search voltage of the photovoltaic cell group and the control voltage of the photovoltaic cell group at the current acquisition moment.

[0071] In order to obtain the control voltage at the next adjacent acquisition moment of the current acquisition moment, it is necessary to first determine the appropriate search step size, and then use the intelligent optimization algorithm to obtain the optimal value of the control voltage at the next adjacent acquisition moment of the current acquisition moment. When the search step size is too small, the maximum power position determined by the intelligent optimization algorithm is prone to fall into the problem of local optimal solution; when the search step size is too large, the process of determining the maximum power position by the intelligent optimization algorithm is prone to affect the stability of the DC microgrid power supply. Therefore, it is necessary to determine the most appropriate search step size for each acquisition moment according to the output characteristics of different photovoltaic cells contained in the photovoltaic battery group, so as to improve the control stability of the DC microgrid.

[0072] First, the basic search step length of each photovoltaic cell is set. In this embodiment, the value of the basic search step length is the product of the rated operating voltage of the photovoltaic cell and 65%. In actual application, as other implementation methods, the implementer can determine the value of the basic search step length according to actual conditions, and this application does not impose any special restrictions.

[0073] For any photovoltaic cell, the search voltage upper limit and the search voltage lower limit of the photovoltaic cell are determined according to the basic search step length of the photovoltaic cell, the positive and negative values ​​of the slope values ​​contained in the output characteristic sequence of the photovoltaic cell, and the output voltage of the number pairs corresponding to the slope contained in the output characteristic sequence.

[0074] For any photovoltaic cell, the output voltage-output power curve of the photovoltaic cell should conform to the law of monotonically increasing first until it reaches the optimal working voltage, and then monotonically decreasing. Among them, the output voltage-output power curve is a curve that takes the output voltage as the independent variable and the output power as the dependent variable to represent the change law between the output power and the output voltage of the photovoltaic cell. At the same time, in the output voltage-output power number pair diagram, the slope of the point represents the monotonicity of the output voltage-output power curve at the acquisition time corresponding to the point. Specifically: when the slope of the point is greater than 0, the output voltage-output power curve increases monotonically; when the slope of the point is less than 0, the output voltage-output power curve decreases monotonically; when the slope of the point is equal to 0, the value of the output voltage-output power curve remains unchanged. Therefore, there are three possible situations in the output characteristic sequence of the photovoltaic cell.

[0075] The first case: the slopes of the points contained in the output characteristic sequence of the photovoltaic cell are all positive. The maximum value of the output voltage of the two pairs corresponding to the last slope in the output characteristic sequence of the photovoltaic cell is recorded as the search voltage lower limit. In the first case, the optimal value of the output voltage of the photovoltaic cell is greater than the search voltage lower limit. The sum of the search voltage lower limit and the basic search step length is recorded as the search voltage upper limit.

[0076] The second case: the slope of the points contained in the output characteristic sequence of the photovoltaic cell contains both positive and negative values. The value range determined by the maximum and minimum values ​​of the collected output voltage of the photovoltaic cell is recorded as the output voltage collection range. At this time, the optimal value of the output voltage of the photovoltaic cell is within the output voltage collection range. Select the last positive slope contained in the output characteristic sequence of the photovoltaic cell, and record the maximum value of the output voltage of the two pairs corresponding to the selected slope as the search voltage lower limit. Select the first negative slope contained in the output characteristic sequence of the photovoltaic cell, and record the minimum value of the output voltage of the two pairs corresponding to the selected slope as the search voltage upper limit.

[0077] The third case: The slopes of the points included in the output characteristic sequence of the photovoltaic cell are all negative. Select the first slope included in the output characteristic sequence of the photovoltaic cell, and record the minimum value of the output voltage of the two pairs corresponding to the selected slope as the search voltage upper limit. At this time, the optimal value of the output voltage of the photovoltaic cell is less than the search voltage upper limit. The difference between the search voltage upper limit and the basic search step length is recorded as the search voltage lower limit.

[0078] In particular, when the search voltage lower limit calculated in the third case is less than 0, the search voltage lower limit is assigned a value of 0.

[0079] Furthermore, the optimal search voltage of the photovoltaic cell group is determined according to the output characteristic weights of all photovoltaic cells included in the photovoltaic cell group, the search voltage upper limit and the search voltage lower limit.

[0080] Preferably, as an embodiment of the present application, the output characteristic weight of the photovoltaic cell is used as the weight of the search voltage upper limit of the photovoltaic cell, and the search voltage upper limits of all photovoltaic cells contained in the photovoltaic cell group are weighted and summed to obtain the optimal search voltage upper limit of the photovoltaic cell group. The output characteristic weight of the photovoltaic cell is used as the weight of the search voltage lower limit of the photovoltaic cell, and the search voltage lower limits of all photovoltaic cells contained in the photovoltaic cell group are weighted and summed to obtain the optimal search voltage lower limit of the photovoltaic cell group. The average of the optimal search voltage upper limit and the optimal search voltage lower limit of the photovoltaic cell group is recorded as the optimal search voltage of the photovoltaic cell group.

[0081] The output characteristic weights of photovoltaic cells are used to perform weighted summation of the upper and lower limits of the photovoltaic cell search voltage. The optimal search voltage of the photovoltaic battery group obtained can effectively avoid the control voltage determination process of the DC microgrid from falling into the local optimal solution, thereby improving the control stability of the DC microgrid.

[0082] The optimal search step length at the current acquisition moment is determined according to the optimal search voltage of the photovoltaic battery group and the control voltage of the photovoltaic battery group at the current acquisition moment.

[0083] Preferably, as an embodiment of the present application, the absolute value of the difference between the optimal search voltage of the photovoltaic cell group and the control voltage of the photovoltaic cell group at the current acquisition moment is recorded as the optimal search step length at the current acquisition moment.

[0084] At this point, the optimal search step size at the current acquisition time is obtained.

[0085] S004: According to the optimal search step, output power and control voltage at the current collection moment, and the basic search step of the photovoltaic cell, the control voltage at the next collection moment of the current collection moment is obtained, and the stability intelligent control of the DC microgrid is realized according to the control voltage at the next collection moment of the current collection moment.

[0086] The dynamic learning rate at the current acquisition moment is determined according to the basic search step length of the photovoltaic cell and the optimal search step length at the current acquisition moment.

[0087] Preferably, as an embodiment of the present application, twice the basic search step size of the photovoltaic cell is used as the upper limit of the search step size of the intelligent optimization algorithm, the ratio of the optimal search step size at the current acquisition moment to the upper limit of the search step size is recorded as the first ratio at the current acquisition moment, and the product of the first ratio at the current acquisition moment and the preset maximum learning rate is recorded as the dynamic learning rate at the current acquisition moment.

[0088] In this embodiment, the preset value of the maximum learning rate is 0.05.

[0089] The output power at the current acquisition moment is used as the objective function, the control voltage at the current acquisition moment is used as the independent variable, and the dynamic learning rate at the current acquisition moment is used as the learning rate. The control voltage at the next acquisition moment of the current acquisition moment is obtained using an intelligent optimization algorithm. At the next acquisition moment of the current acquisition moment, the internal resistance of the photovoltaic battery group is adjusted so that the control voltage at the next acquisition moment of the current acquisition moment is equal to the control voltage at the next acquisition moment of the current acquisition moment obtained using the intelligent optimization algorithm, thereby realizing intelligent control of the stability of the DC microgrid.

[0090] Among them, this embodiment uses the stochastic gradient descent algorithm as the intelligent optimization algorithm. As other implementation methods, on the basis of the purpose of obtaining the optimal value of the control voltage, the implementer can adopt other methods in the prior art such as particle swarm optimization algorithm, Harris eagle optimization algorithm, whale optimization algorithm and sparrow search algorithm to obtain the optimal value of the control voltage, and this application does not make special restrictions. At the same time, it can be understood that the meaning of taking twice the basic search step length of the photovoltaic cell as the upper limit of the search step length of the intelligent optimization algorithm is: when the optimal search step length at the current acquisition moment is greater than twice the basic search step length of the photovoltaic cell, the optimal search step length at the current acquisition moment is taken as twice the basic search step length of the photovoltaic cell, so as to avoid the problem that the optimal search voltage of the photovoltaic cell group is inaccurately determined due to the excessive value of the optimal search step length at the current acquisition moment.

[0091] At this point, the intelligent control of the stability of the DC microgrid is realized, that is, the optimal control of the DC microgrid.

[0092] See also Figure 5 , Figure 5 1 is a schematic diagram of the structure of an optimization control device for a DC microgrid provided by an embodiment of the present application. In this embodiment, the device includes various units for executing various steps in an embodiment corresponding to an optimization control method for a DC microgrid. Figure 5 ,The optimization control device includes : a grid photovoltaic data acquisition module, a photovoltaic output ,characteristics analysis module, a control voltage search step length determination module, and a DC microgrid control module.

[0093] The power grid photovoltaic data acquisition module is used to collect the control voltage of the photovoltaic battery group at the current acquisition time and the output voltage and output power of each photovoltaic cell in the photovoltaic battery group at the current acquisition time and at different acquisition times in the previous local time period;

[0094] The photovoltaic output characteristic analysis module is used to determine the number pairs at the same collection time according to the output voltage and output power of the photovoltaic cell at the same collection time, determine the output characteristic sequence of the photovoltaic cell according to the number pairs of the photovoltaic cell at all collection times, and determine the output characteristic weight of the photovoltaic cell according to the similarity between the output characteristic sequence of the photovoltaic cell and the output characteristic sequences of all other photovoltaic cells;

[0095] A control voltage search step determination module is used to determine the search voltage upper limit and the search voltage lower limit of the photovoltaic cell according to the preset basic search step of the photovoltaic cell, the positive and negative values ​​of the slope values ​​contained in the output characteristic sequence of the photovoltaic cell, and the output voltage of the number pair corresponding to the slope contained in the output characteristic sequence, determine the optimal search voltage of the photovoltaic cell group according to the output characteristic weights of all photovoltaic cells contained in the photovoltaic cell group, the search voltage upper limit and the search voltage lower limit, and determine the optimal search step at the current acquisition time according to the optimal search voltage of the photovoltaic cell group and the control voltage of the photovoltaic cell group at the current acquisition time;

[0096] The DC microgrid control module is used to obtain the control voltage at the next collection moment of the current collection moment according to the optimal search step, output power and control voltage at the current collection moment, as well as the basic search step of the photovoltaic cell, and realize intelligent control of the stability of the DC microgrid according to the control voltage at the next collection moment of the current collection moment.

[0097] Based on the same inventive concept as the above method, an embodiment of the present application also provides an optimization control system for a DC microgrid, comprising a memory, a processor, and a computer program stored in the memory and running on the processor, wherein when the processor executes the computer program, the steps of any one of the above-mentioned optimization control methods for a DC microgrid are implemented.

[0098] It is to be understood that the sequence of the embodiments of the present application described above is for description only and does not represent the advantages and disadvantages of the embodiments. The above describes specific embodiments of the present specification. In addition, the processes depicted in the accompanying drawings do not necessarily require the specific order or continuous order shown to achieve the desired results. In some embodiments, multitasking and parallel processing are also possible or may be advantageous.

[0099] The various embodiments in this specification are described in a progressive manner, and the same or similar parts between the various embodiments can be referenced to each other, and each embodiment focuses on the differences from other embodiments.

[0100] The above content is only an implementation method of the present application and is not intended to limit the scope of the present application. Any equivalent structure or equivalent process transformation made using the contents of the present application specification and drawings, or directly or indirectly used in other related technical fields, are also included in the protection scope of the present application.

Claims

1. An optimization control method for a DC microgrid, characterized in that: The method comprises the following steps: Collecting the control voltage of the photovoltaic battery group at the current collection time and the output voltage and output power of each photovoltaic battery in the photovoltaic battery group at the current collection time and at different collection times in the previous local time period; According to the output voltage and output power of the photovoltaic cell at the same collection time, the number pairs at the same collection time are determined; according to the number pairs of the photovoltaic cell at all collection times, the output characteristic sequence of the photovoltaic cell is determined; according to the similarity between the output characteristic sequence of the photovoltaic cell and the output characteristic sequences of all other photovoltaic cells, the output characteristic weight of the photovoltaic cell is determined; According to the preset basic search step of the photovoltaic cell, the positive and negative slope values ​​contained in the output characteristic sequence of the photovoltaic cell, and the output voltage of the number pair corresponding to the slope contained in the output characteristic sequence, the search voltage upper limit and the search voltage lower limit of the photovoltaic cell are determined; according to the output characteristic weights of all photovoltaic cells contained in the photovoltaic cell group, the search voltage upper limit and the search voltage lower limit, the optimal search voltage of the photovoltaic cell group is determined; according to the optimal search voltage of the photovoltaic cell group and the control voltage of the photovoltaic cell group at the current collection time, the optimal search step at the current collection time is determined; According to the optimal search step, output power and control voltage at the current collection moment, and the basic search step of the photovoltaic cell, the control voltage at the next collection moment of the current collection moment is obtained, and according to the control voltage at the next collection moment of the current collection moment, the stability of the DC microgrid is intelligently controlled.

2. The optimization control method for a DC microgrid according to claim 1, characterized in that: The specific process of determining the number pairs at the same collection time according to the output voltage and output power of the photovoltaic cell at the same collection time, and determining the output characteristic sequence of the photovoltaic cell according to the number pairs of the photovoltaic cell at all collection times is as follows: The number of pairs consisting of the output voltage and output power of the photovoltaic cell at the same collection time is recorded as the number of pairs of the photovoltaic cell at the same collection time, the number of pairs with the same output voltage of the photovoltaic cell at all collection times is selected, the average value of the output power of the selected number of pairs and the output voltage are used to form a new number pair, and the new number pair is used to replace the number pair with the same output voltage; Using the output voltage as the horizontal axis and the output power as the vertical axis, marking all number pairs of any photovoltaic cell in a plane rectangular coordinate system, and obtaining an output voltage-output power number pair graph of any photovoltaic cell; In the output voltage-output power pair diagram, points in the output voltage-output power pair diagram are selected in the order of output voltage from small to large, and the points in the output voltage-output power pair diagram are marked with natural numbers starting from 1 in the order of selection; starting from the point with sequence number 2, each point is recorded as a target point, and the slope between the target point and the point with a sequence number less than 1 than the target point is recorded as the slope of the target point; the slopes of all points are arranged in the order of the sequence numbers of the points from small to large, and the output characteristic sequence of the photovoltaic cell is obtained.

3. The optimization control method for a DC microgrid according to claim 1, characterized in that: The construction process of the output characteristic weight of the photovoltaic cell is: The cosine similarity between the output characteristic sequences of two different photovoltaic cells is recorded as the first output characteristic weights of the two different photovoltaic cells, the average of the first output characteristic weights of any photovoltaic cell and all other photovoltaic cells is recorded as the second output characteristic weight of any photovoltaic cell, and the normalized value of the second output characteristic weight of any photovoltaic cell is recorded as the output characteristic weight of any photovoltaic cell.

4. The optimization control method for a DC microgrid according to claim 2, characterized in that: The specific process of determining the search voltage upper limit and the search voltage lower limit of the photovoltaic cell according to the preset basic search step length of the photovoltaic cell, the positive and negative values ​​of the slope values ​​contained in the output characteristic sequence of the photovoltaic cell, and the output voltage of the number pairs corresponding to the slopes contained in the output characteristic sequence is as follows: There are three possible situations in the output characteristic sequence of photovoltaic cells: the slopes of the points contained in the output characteristic sequence of photovoltaic cells are all positive, all negative, or both positive and negative; According to three possible situations of the output characteristic sequence of the photovoltaic cell, the search voltage upper limit and the search voltage lower limit of the photovoltaic cell are determined respectively.

5. The optimization control method for a DC microgrid according to claim 4, characterized in that: The specific process of determining the upper and lower limits of the search voltage of the photovoltaic cell according to the three possible situations of the output characteristic sequence of the photovoltaic cell is as follows: When the slopes of the points contained in the output characteristic sequence of the photovoltaic cell are all positive values: the maximum value of the output voltages of the two number pairs corresponding to the last slope in the output characteristic sequence of the photovoltaic cell is recorded as the search voltage lower limit, and the sum of the search voltage lower limit and the basic search step length is recorded as the search voltage upper limit; When the slope of the points included in the output characteristic sequence of the photovoltaic cell contains both positive and negative values: select the last positive slope included in the output characteristic sequence of the photovoltaic cell, record the maximum value of the output voltage of the two number pairs corresponding to the selected slope as the search voltage lower limit, select the first negative slope included in the output characteristic sequence of the photovoltaic cell, record the minimum value of the output voltage of the two number pairs corresponding to the selected slope as the search voltage upper limit; When the slopes of the points included in the output characteristic sequence of the photovoltaic cell are all negative values: select the first slope included in the output characteristic sequence of the photovoltaic cell, record the minimum value of the output voltage of the two number pairs corresponding to the selected slope as the search voltage upper limit, and record the difference between the search voltage upper limit and the basic search step as the search voltage lower limit.

6. The optimization control method for a DC microgrid according to claim 1, characterized in that: The specific process of determining the optimal search voltage of the photovoltaic battery group according to the output characteristic weights of all photovoltaic batteries included in the photovoltaic battery group, the search voltage upper limit and the search voltage lower limit is as follows: The output characteristic weight of the photovoltaic cell is used as the weight of the search voltage upper limit of the photovoltaic cell, and the search voltage upper limits of all photovoltaic cells included in the photovoltaic cell group are weighted and summed to obtain the optimal search voltage upper limit of the photovoltaic cell group; The output characteristic weight of the photovoltaic cell is used as the weight of the search voltage lower limit of the photovoltaic cell, and the search voltage lower limits of all photovoltaic cells included in the photovoltaic cell group are weighted and summed to obtain the optimal search voltage lower limit of the photovoltaic cell group; The average of the upper limit of the optimal search voltage and the lower limit of the optimal search voltage of the photovoltaic battery group is recorded as the optimal search voltage of the photovoltaic battery group.

7. The optimization control method for a DC microgrid according to claim 1, characterized in that: The specific process of determining the optimal search step length at the current acquisition time according to the optimal search voltage of the photovoltaic battery group and the control voltage of the photovoltaic battery group at the current acquisition time is as follows: The absolute value of the difference between the optimal search voltage of the photovoltaic battery group and the control voltage of the photovoltaic battery group at the current acquisition time is recorded as the optimal search step length at the current acquisition time.

8. The optimization control method for a DC microgrid according to claim 1, characterized in that: According to the optimal search step size, output power and control voltage at the current acquisition moment, and the basic search step size of the photovoltaic cell, the control voltage at the next acquisition moment of the current acquisition moment is obtained, and the stability intelligent control of the DC microgrid is realized according to the control voltage at the next acquisition moment of the current acquisition moment. The specific process of obtaining is: The twice of the basic search step of the photovoltaic cell is taken as the upper limit of the search step of the intelligent optimization algorithm, the ratio of the optimal search step at the current acquisition time to the upper limit of the search step is recorded as the first ratio at the current acquisition time, and the product of the first ratio at the current acquisition time and the preset maximum learning rate is recorded as the dynamic learning rate at the current acquisition time; The output power at the current acquisition moment is taken as the objective function, the control voltage at the current acquisition moment is taken as the independent variable, the dynamic learning rate at the current acquisition moment is taken as the learning rate, and the intelligent optimization algorithm is used to obtain the control voltage at the next acquisition moment of the current acquisition moment; At the next collection moment of the current collection moment, the internal resistance of the photovoltaic battery group is adjusted so that the control voltage at the next collection moment of the current collection moment is equal to the control voltage at the next collection moment of the current collection moment obtained using the intelligent optimization algorithm, thereby realizing intelligent control of the stability of the DC microgrid.

9. An optimization control device for a DC microgrid, implementing the method according to claim 1, characterized in that: The optimization control device comprises: The power grid photovoltaic data acquisition module is used to collect the control voltage of the photovoltaic battery group at the current acquisition time and the output voltage and output power of each photovoltaic cell in the photovoltaic battery group at the current acquisition time and at different acquisition times in the previous local time period; The photovoltaic output characteristic analysis module is used to determine the number pairs at the same collection time according to the output voltage and output power of the photovoltaic cell at the same collection time, determine the output characteristic sequence of the photovoltaic cell according to the number pairs of the photovoltaic cell at all collection times, and determine the output characteristic weight of the photovoltaic cell according to the similarity between the output characteristic sequence of the photovoltaic cell and the output characteristic sequences of all other photovoltaic cells; A control voltage search step determination module is used to determine the search voltage upper limit and the search voltage lower limit of the photovoltaic cell according to the preset basic search step of the photovoltaic cell, the positive and negative values ​​of the slope values ​​contained in the output characteristic sequence of the photovoltaic cell, and the output voltage of the number pair corresponding to the slope contained in the output characteristic sequence, determine the optimal search voltage of the photovoltaic cell group according to the output characteristic weights of all photovoltaic cells contained in the photovoltaic cell group, the search voltage upper limit and the search voltage lower limit, and determine the optimal search step at the current acquisition time according to the optimal search voltage of the photovoltaic cell group and the control voltage of the photovoltaic cell group at the current acquisition time; The DC microgrid control module is used to obtain the control voltage at the next collection moment of the current collection moment according to the optimal search step, output power and control voltage at the current collection moment, as well as the basic search step of the photovoltaic cell, and realize intelligent control of the stability of the DC microgrid according to the control voltage at the next collection moment of the current collection moment.

10. An optimization control system for a DC microgrid, comprising a memory, a processor, and a computer program stored in the memory and running on the processor, characterized in that: When the processor executes the computer program, the steps of the method according to any one of claims 1 to 8 are implemented.

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