Grid-connected control method and device for smart power grid, and medium

Abstract

The invention relates to the technical field of power grid intelligent planning, in particular to a grid-connected control method and device for an intelligent power grid and a medium, and the method comprises the steps: obtaining the voltage amplitudes and phase angles of two ends of an inverter and the impedance of a micro-grid feeder line when a micro-grid has a grid-connected demand; presetting an analysis window of a sampling moment; comprehensively analyzing the difference between the voltage amplitudes at the two ends of the inverter in the window and the fluctuation degree of the phase angle to obtain a collaborative deviation; obtaining a synchronous adjustment degree based on the change characteristics of the impedance on the micro-grid feeder line between adjacent sampling moments; and based on the synchronization adjustment degree and the grid-connected state of the micro-grid, obtaining an adaptive proportionality coefficient and an adaptive integral coefficient, and performing droop control on the micro-grid by adopting PI control. The invention aims to dynamically adjust the voltage and the frequency of the micro-grid, realize rapid synchronous control, and prevent the operation stability of the micro-grid and a large power grid from being interfered by overshoot oscillation.

Description

Technical Field

[0001] The present application relates to the technical field of smart grid planning, and in particular to a grid connection control method, device and medium for smart grids. Background Art

[0002] Grid connection refers to connecting multiple power systems or power generation sources together to achieve resource sharing, improve economic benefits and system stability. It promotes the use of renewable energy, enhances the reliability of power supply, optimizes energy distribution through flexible scheduling, promotes technological innovation and intelligent development, and thus has a positive impact on the efficiency and sustainability of modern power systems. At the current stage, the operation modes of microgrids mainly include island operation and grid-connected operation.

[0003] When the microgrid switches from island mode to grid-connected mode, grid-connected synchronization is required to ensure that the voltage and frequency between the microgrid and the large grid can be effectively matched. In the traditional grid-connected process, an active synchronization method based on droop control is usually used to achieve smooth switching and grid-connected operation control. However, this method often relies on a fixed proportional-integral (PI) coefficient for adjustment and cannot be optimized for the actual operating state of each microgrid, which may lead to synchronization deviation when switching the operating mode, thereby causing overload current and affecting the operating stability between the microgrid and the large grid. Summary of the invention

[0004] In view of the above, it is necessary to provide a grid-connected control method, device and medium for smart grid to solve the above problems.

[0005] According to one aspect of the present application, a smart grid-oriented grid connection control method is provided, the method comprising:

[0006] When the microgrid has a grid-connected demand, the voltage amplitude and phase angle at both ends of each inverter and the impedance of the microgrid feeder are obtained at each sampling moment;

[0007] Preset the analysis window of each sampling moment; comprehensively analyze the differences in the voltage amplitude and phase angle fluctuation degree at both ends of the inverter within the analysis window of each sampling moment to obtain the coordinated deviation of each sampling moment;

[0008] Based on the impedance variation characteristics of the microgrid feeder at each sampling moment and the adjacent sampling moments, combined with the coordination deviation at each sampling moment, the synchronization adjustment degree at each sampling moment is obtained;

[0009] Based on the synchronization adjustment degree at each sampling moment and the grid-connected state of the microgrid, the adaptive proportional coefficient and the adaptive integral coefficient at each sampling moment are obtained, and PI control is used to perform droop control on the microgrid.

[0010] Wherein, the two ends of the inverter include a microgrid end and a large grid end.

[0011] The coordinated deviation at each sampling moment is obtained as follows:

[0012] According to the difference of voltage amplitude fluctuation degree between the inverter microgrid end and the large grid end in the analysis window at each sampling moment, the double-terminal stability at each sampling moment is obtained;

[0013] A first sequence consisting of all voltage phase angles at the inverter microgrid end and a second sequence consisting of all voltage phase angles at the large grid end in the analysis window at each sampling moment are obtained respectively; the coordinated deviation at each sampling moment is obtained according to the distance measurement between the first sequence and the second sequence and the negative correlation mapping result of the two-end stability.

[0014] The double-end stability at each sampling moment is obtained as follows:

[0015] The negative correlation mapping result after merging the fluctuation degree of all voltage amplitudes at the inverter microgrid end and the large grid end in the analysis window at each sampling moment is taken as the double-terminal stability at each sampling moment.

[0016] The synchronization adjustment degree of each sampling moment is obtained as follows:

[0017] Obtain the feeder interference degree at each sampling moment according to the impedance difference between each sampling moment and the adjacent sampling moments;

[0018] The normalized value of the fusion of the coordination deviation and feeder interference degree of each microgrid at each sampling moment is used as the synchronization adjustment degree at each sampling moment.

[0019] The feeder interference degree at each sampling moment is specifically the modulus of the difference between the feeder impedance at each sampling moment and the feeder impedance at the previous sampling moment.

[0020] The process of obtaining the adaptive proportional coefficient and the adaptive integral coefficient at each sampling moment includes:

[0021] Based on the grid-connected state of the microgrid at each sampling moment, the grid-connected state control coefficient at each sampling moment is obtained, which is recorded as ε;

[0022] The formulas for the adaptive proportional coefficient and adaptive integral coefficient at each sampling moment are:

[0023]

[0024] In the formula, K p , K I Respectively represent the adaptive proportional coefficient and adaptive integral coefficient at each sampling time, K p0 , KI0 They represent the initial proportional coefficient and the initial integral coefficient respectively, η represents the synchronization adjustment degree at the current sampling moment, ΔP and ΔI represent the preset proportional distance and the preset integral distance respectively.

[0025] The specific process of obtaining the grid-connected state control coefficient is as follows:

[0026] When the microgrid is not connected to the large grid, the first preset value is used as the grid-connected state control coefficient at the corresponding sampling moment; otherwise, the second preset value is used as the grid-connected state control coefficient at the corresponding sampling moment, wherein the first preset value is greater than the second preset value.

[0027] According to another aspect of the present invention, a smart grid-oriented grid-connected control device is provided, comprising:

[0028] Grid-connected data acquisition module: used to obtain the voltage amplitude and phase angle at both ends of each inverter and the impedance of the microgrid feeder at each sampling moment when the microgrid has a grid-connected demand;

[0029] Grid-connected data analysis module: used to preset the analysis window of each sampling moment; comprehensively consider the differences in the voltage amplitude and phase angle fluctuation degree at both ends of the inverter within the analysis window of each sampling moment, and obtain the coordination deviation of each sampling moment; based on the impedance variation characteristics on the microgrid feeder at each sampling moment and the adjacent sampling moment, combined with the coordination deviation of each sampling moment, obtain the synchronization adjustment degree of each sampling moment;

[0030] Grid-connected control module: used to obtain the adaptive proportional coefficient and adaptive integral coefficient at each sampling moment based on the synchronization adjustment degree at each sampling moment and the grid-connected state of the microgrid, and use PI control to perform droop control on the microgrid.

[0031] According to another aspect of the present application, a grid-connected control medium for a smart grid is provided, 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-mentioned methods when executing the computer program.

[0032] In the above scheme, when the microgrid has a grid-connected demand, the voltage amplitude, phase angle and impedance of the microgrid feeder at both ends of each inverter at each sampling moment are obtained to provide a data basis for the subsequent dynamic adjustment of the voltage and frequency of the microgrid; the analysis window of each sampling moment is preset; the differences in the voltage amplitude and phase angle fluctuation degree at both ends of the inverter within the analysis window of each sampling moment are comprehensively considered to obtain the coordination deviation of each sampling moment, which has the beneficial effect of reflecting the difference coordination of voltage and phase when the microgrid and the large grid need to be synchronized at each sampling moment; based on the impedance of the microgrid feeder at each sampling moment and the adjacent sampling moment The change characteristics are combined with the coordinated deviation at each sampling moment to obtain the synchronization adjustment degree at each sampling moment, which reflects the impact of impedance change fluctuations on grid-connected synchronization on the feeder line, and measures the adjustment strength of grid-connected synchronization control at each sampling moment; based on the synchronization adjustment degree at each sampling moment and the grid-connected status of the microgrid, the adaptive proportional coefficient and adaptive integral coefficient at each sampling moment are obtained, and PI control is used to perform droop control on the microgrid. The beneficial effect is that the voltage and frequency of the microgrid can be dynamically adjusted to achieve rapid synchronization control and avoid overshoot oscillation interfering with the operation stability of the microgrid and the large grid. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 A flowchart of a smart grid-oriented grid connection control method provided in this application;

[0034] Figure 2 A schematic diagram of the frequency control effect provided for this application;

[0035] Figure 3 A block diagram of a grid-connected control device for a smart grid provided in this application. DETAILED DESCRIPTION

[0036] In the description of the embodiments of the present application, words such as "exemplary", "or", "for example" and the like are used to indicate examples, illustrations or descriptions. Any embodiment or design described as "exemplary" or "for example" in the embodiments of the present application should not be interpreted as being more preferred or more advantageous than other embodiments or designs. Specifically, the use of words such as "exemplary", "or", "for example" and the like is intended to present related concepts in a concrete manner.

[0037] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art in the present application. The terms used in the specification of the present application are only for the purpose of describing specific embodiments and are not intended to limit the present application.

[0038] It should also be noted that the terms "first" and "second" in this application and the accompanying drawings are used to distinguish similar objects, rather than to describe a specific order or sequence. The method disclosed in the embodiments of the present application or the method shown in the flowchart includes one or more steps for implementing the method. Without departing from the scope of the present application, the execution order of multiple steps can be interchanged with each other, and some steps can also be deleted.

[0039] See also Figure 1 , which shows a flowchart of a grid connection control method for a smart grid provided by an embodiment of the present application, the method comprising the following steps:

[0040] Step 1: When the microgrid has a grid-connected demand, the voltage amplitude and phase angle at both ends of each inverter and the impedance of the microgrid feeder are obtained at each sampling moment.

[0041] To effectively control and manage the distributed power sources in the microgrid, it is necessary to obtain the operating data of each distributed power source and the operating status of the large power grid. This application takes the grid connection control of a microgrid in a certain area and a large power grid as the research object, wherein the microgrid of this application is specifically a renewable energy power generation source, such as wind power generation and solar power generation. This application analyzes the parallel control of multiple microgrids and a large power grid.

[0042] When the power of a single distributed power source can meet the internal load demand, it can be selected to be connected to the grid and the excess power can be output to the grid. Taking a distributed power source that needs to be connected to the grid as an example, the voltage and current of the microgrid output end and the inverter microgrid end are obtained through voltage sensors and current sensors respectively; since the inverter is connected to the grid, the voltage of the inverter large grid end is obtained. In this embodiment, the sampling interval of the voltage sensor and the current sensor is set to 10ms; the implementer can adjust it according to the actual situation. It should be noted that since the microgrid and the large grid are alternating current, the collected voltage and current are expressed in the form of polar coordinates. For example, the voltage is expressed in In the form of represents the voltage amplitude, and ∠θ represents the phase angle.

[0043] The impedance on the feeder is obtained by using Ampere's law, and the impedance is expressed in complex form, with the real part being the resistance value and the imaginary part being the reactance value. It should be noted that Ampere's law is a known technology, and this application will not elaborate on it.

[0044] Step 2: Preset the analysis window for each sampling moment; comprehensively analyze the differences in the voltage amplitude and phase angle fluctuation degree across the inverter within the analysis window at each sampling moment to obtain the coordinated deviation at each sampling moment.

[0045] A microgrid is a small, low-voltage power generation and distribution network that generates electricity mainly through clean energy to provide power for loads in a specific area. When the power generation is sufficient, the microgrid can switch to the grid-connected operation mode and connect to the large grid to achieve optimal use of electric energy. When the grid is connected, the distributed power sources of the microgrid must be synchronized with the grid. This means that the voltage and frequency of the microgrid output need to be adjusted to ensure that they meet the standards of the large grid. When the voltage and frequency errors meet the requirements, the grid connection switching can be completed. Once the grid connection is successful, since the stability of power generation in the microgrid may be affected by fluctuations, it is necessary to continuously monitor and adjust the voltage and frequency of the microgrid in real time to ensure that it is synchronized with the large grid. This can effectively ensure the stability and reliability of the power supply. Since the power generation type and power generation efficiency of each distributed power source are different, different control parameters are matched to each microgrid during grid connection control, and dynamic adjustments need to be made in combination with the operating conditions of the microgrid and the large grid.

[0046] In actual practice, the difference between the microgrid and the large grid is mainly reflected by the voltage difference at both ends of the inverter. Since the microgrid has internal loads, the power generation efficiency of the microgrid may be affected by environmental factors. Therefore, the stability of the microgrid can be reflected by the voltage fluctuation at the microgrid end of the inverter. At the same time, within the large grid, ideally, the voltage and frequency should be kept at a fixed value, but in the large grid, due to the existence of nonlinear factors and complex interactions, harmonic interference is easily introduced, resulting in fluctuations and differences in the voltage of the inverter at the large grid end. The greater the difference in fluctuations between the two, the greater the adjustment required during synchronization.

[0047] Based on this, each sampling moment and the previously preset number of sampling moments are used as the analysis windows of each sampling moment; the preset number in this embodiment is 20, and the implementer can select it according to the actual situation; the fluctuation degree of all voltage amplitudes at the inverter microgrid end and the large grid end in the analysis window of each sampling moment is fused, and the negative correlation mapping result is used as the two-terminal stability of each sampling moment.

[0048] In the process of acquiring the double-end stability of this embodiment, the variance of the voltage amplitude at the inverter microgrid end in the analysis window at each sampling moment is recorded as the first fluctuation degree; the variance of the voltage amplitude at the inverter large grid end in the analysis window at each sampling moment is recorded as the second fluctuation degree; the voltage fluctuation degree is integrated by calculating the sum of the first fluctuation degree and the second fluctuation degree; the double-end stability is specifically the inverse of the sum.

[0049] It should be noted that when the sum of the first fluctuation degree and the second fluctuation degree is equal to 0, the value of the double-end stability is set to 20; if there is a situation where the sampling moments before a sampling moment are less than the preset number, the calculation is based on all moments before the sampling moment.

[0050] At both ends of the inverter, if the power generation efficiency of the microgrid is affected by environmental fluctuations, the output voltage will fluctuate greatly, and the voltage amplitude in the local voltage sequence of the microgrid will fluctuate greatly. Similarly, if the large power grid is greatly affected by harmonics, the voltage amplitude in the local voltage sequence of the inverter large power grid will fluctuate greatly, and the double-end stability will be small.

[0051] The two-end stability can reflect the voltage fluctuation at both ends of the inverter at the current sampling moment. However, when the microgrid is synchronized with the grid, the voltage and frequency at both ends of the inverter need to be kept consistent. Therefore, it is necessary to calculate the difference in the coordinated fluctuations at both ends, that is, the difference in the phase angle at both ends of the inverter. If the relative consistency of the phase angle at both ends of the inverter is poor, it means that the voltage phase angle difference between the microgrid and the large grid is large, and it is difficult to achieve grid synchronization, so the intensity of regulation needs to be increased.

[0052] Based on this, a sequence consisting of all voltage phase angles at the inverter microgrid end in the analysis window at each sampling moment is obtained, which is recorded as the first sequence; a sequence consisting of all voltage phase angles at the inverter large grid end in the analysis window at each sampling moment is obtained, which is recorded as the second sequence; according to the distance measurement between the first sequence and the second sequence, combined with the negative correlation mapping result of the two-end stability, the coordinated deviation at each sampling moment is obtained.

[0053] In the process of obtaining the collaborative deviation of this embodiment, the distance metric between the two sequences is measured by the dynamic time warping (DTW) distance; the negative correlation mapping of the two-end stability is specifically the inverse of the two-end stability; the collaborative deviation is specifically the product of the DTW distance and the inverse. In some other embodiments, the Euclidean distance can be used as the distance metric between sequences; in some other embodiments, the Manhattan distance can be used as the distance metric between sequences.

[0054] It should be understood that if the DTW distance of the phase angle in the local voltage sequence at both ends of the inverter is larger in the local voltage sequence constructed at the current sampling moment, it indicates that at the current sampling moment, the voltage phase angle difference between the microgrid and the large grid is not stable enough and the variation is large. This means that the synchronization between the two is poor, which may lead to instability in system operation. Often at this time, the fluctuation of the voltage amplitude of the local voltage sequence of the microgrid and the large grid at both ends of the inverter is large, resulting in a small double-end stability, and finally a large value of the coordinated deviation. On the contrary, if the microgrid and the large grid at both ends of the inverter at the current sampling moment can remain relatively stable, the voltage amplitude and phase angle in the voltage sequence at both ends can remain relatively stable, and the value of the coordinated deviation is small.

[0055] Step 3: Based on the change characteristics of the impedance on the microgrid feeder at each sampling moment and the adjacent sampling moments, combined with the coordination deviation at each sampling moment, the synchronization adjustment degree at each sampling moment is obtained.

[0056] The coordinated deviation at each sampling moment is reflected in the fluctuation stability of the voltage at both ends of the inverter, which indirectly reflects the difficulty of grid-connected synchronous regulation at each sampling moment. However, the distance between different microgrids and the large grid is different, and the filtering on the feeder is different, resulting in inconsistent impedance on the feeder of different microgrids.

[0057] On the feeder, the main purpose is to transmit the electric energy of the microgrid to the large grid to achieve power transmission. In order to ensure that the power fluctuation during transmission is small, filtering equipment such as inductors and capacitors are usually introduced on the feeder. Therefore, the impedance on the feeder is in complex form and mainly consists of two parts: on the one hand, the equivalent resistance generated by the attenuation caused during the line transmission process, which represents the real part of the impedance; on the other hand, the reactance part formed by the introduction of reactive elements such as inductors and capacitors constitutes the imaginary part of the impedance.

[0058] The power generation frequency of the microgrid is greatly affected by the power generation efficiency, which causes the impedance on the feeder to fluctuate. Therefore, the impedance fluctuation needs to be taken into account in the grid-connected control. If the impedance fluctuation is larger, it means that the feeder has a greater impact on the voltage and phase of the microgrid output, and the adjustment strength needs to be increased; on the contrary, if the impedance fluctuation is smaller or basically remains unchanged, it means that the feeder has a smaller impact on the voltage at this time, and only the output of the microgrid needs to be considered, and the corresponding synchronous control is relatively easy.

[0059] Based on this, the feeder interference degree at each sampling moment is obtained according to the impedance difference between each sampling moment and the adjacent sampling moment. In obtaining the feeder interference degree in this embodiment, the impedance difference is measured by the modulus of the difference between the feeder impedance at each sampling moment and the previous sampling moment.

[0060] If the impedance difference between adjacent sampling moments of the microgrid is large, the value of the feeder interference degree is large. At adjacent sampling moments, if the power generation of the microgrid is unstable, the feeder may be greatly disturbed. This interference will increase the deviation between the voltage and phase angle output by the microgrid and the large power grid, thereby affecting the overall stability and power supply quality of the system. On the contrary, if the impedance difference between two adjacent sampling moments is small, the value of the feeder interference degree is small, indicating that the interference ability of the feeder is weak, so the intensity of synchronous control can be appropriately reduced.

[0061] Furthermore, the synchronization adjustment degree at each sampling moment is obtained by combining the coordination deviation at each sampling moment: the normalized value of the fusion of the coordination deviation at each sampling moment of each microgrid and the feeder interference degree is used as the synchronization adjustment degree at each sampling moment.

[0062] In this embodiment, the coordination deviations of all microgrids at each sampling moment are used as weights, and the feeder interference degree is weighted and summed to obtain a normalized value to obtain the synchronization adjustment degree at each sampling moment, wherein the normalization adopts a sigmoid function.

[0063] The control strength of proportional integral is reflected by the synchronization adjustment degree. If the operation of the microgrid and the large power grid is relatively stable, the value of the synchronization adjustment degree is small. On the contrary, if the operation difference between the microgrid and the large power grid is large and the coordination between the two is poor due to environmental fluctuations, the value of the synchronization adjustment degree is large.

[0064] Step 4: Based on the synchronization adjustment degree at each sampling moment and the grid-connected state of the microgrid, the adaptive proportional coefficient and the adaptive integral coefficient at each sampling moment are obtained, and the PI control is used to perform droop control on the microgrid.

[0065] The synchronization adjustment degree reflects the stability of the operating status between the microgrid and the large power grid. It is necessary to adjust the intensity of synchronization control and obtain the adaptive proportional integral coefficient at each sampling time in combination with the grid-connected operating status. The formula is:

[0066]

[0067] In the formula, K p , K I Respectively represent the adaptive proportional coefficient and adaptive integral coefficient at each sampling moment, K p0 , K I0 They represent the initial proportional coefficient and the initial integral coefficient respectively. In this embodiment, K is set p0 =5, K I0=50; ε represents the grid-connected state control coefficient. When not connected to the grid, ε=3. If connected to the grid, ε=1; η represents the synchronization adjustment degree at the current sampling moment. ΔP and ΔI represent the proportional distance and the integral distance respectively. In this scheme, ΔP=10 and ΔI=50 are set.

[0068] When not connected to the grid, there is usually a significant difference between the microgrid and the large grid. In this case, a higher grid-connected state control coefficient needs to be set so that the adaptive proportional integral coefficient can be increased accordingly. When the voltage and phase angle difference between the microgrid and the large grid is large and the stability is insufficient, the calculated synchronization adjustment value will increase significantly. This indicates that the difference between the two is high, so in order to achieve fast synchronization, a larger adaptive proportional and integral coefficient must be configured.

[0069] In the case of grid connection, there may be a certain difference between the synchronized microgrid and the large grid due to the poor stability of the microgrid, but the difference between the two is often relatively small. At this time, a smaller grid connection state coefficient is set to obtain a smaller adaptive proportion and integral coefficient to avoid overshoot oscillation.

[0070] The voltage amplitude and phase angle difference between the microgrid and the large grid at the current sampling moment is calculated, and the voltage amplitude and phase angle that need to be adjusted are obtained by using the PI control algorithm, and the active power and reactive power of the microgrid that need to be adjusted are calculated by using the droop control principle, thereby reducing the difference between the microgrid and the large grid at both ends of the inverter. It should be noted that the droop control principle is an existing well-known technology, and this application will not elaborate on it.

[0071] PI control is used to adjust the voltage and frequency of the microgrid after the grid connection demand exists. When the voltage amplitude and phase angle difference between the microgrid and the large grid are less than the preset threshold, the microgrid is connected to the large grid to achieve grid connection switching. At the same time, after the grid connection, PI control is used to achieve active synchronous following of the voltage and frequency of the microgrid. The preset threshold is 0.1%; the implementer can set it according to the actual situation.

[0072] Among them, the frequency control effect diagram is as follows: Figure 2 As shown, the horizontal axis represents time in seconds, and the vertical axis represents frequency in Hertz. If there is a grid-connected demand at the 0th second, the frequency between the microgrids is not consistent with the large grid. Active synchronization is used to adjust the frequency of the microgrid to achieve grid-connected switching. After grid-connected, the output frequency of the microgrid may deviate due to the fluctuation of the microgrid, and it can also be quickly synchronized to avoid overshoot and oscillation.

[0073] Based on the same concept as the method embodiment of the present application, a grid-connected control device for a smart grid is proposed, comprising:

[0074] Grid-connected data acquisition module: used to obtain the voltage amplitude and phase angle at both ends of each inverter and the impedance of the microgrid feeder at each sampling moment when the microgrid has a grid-connected demand;

[0075] Grid-connected data analysis module: used to preset the analysis window of each sampling moment; comprehensively consider the differences in the voltage amplitude and phase angle fluctuation degree at both ends of the inverter within the analysis window of each sampling moment, and obtain the coordination deviation of each sampling moment; based on the impedance variation characteristics on the microgrid feeder at each sampling moment and the adjacent sampling moment, combined with the coordination deviation of each sampling moment, obtain the synchronization adjustment degree of each sampling moment;

[0076] Grid-connected control module: used to obtain the adaptive proportional coefficient and adaptive integral coefficient at each sampling moment based on the synchronization adjustment degree at each sampling moment and the grid-connected state of the microgrid, and use PI control to perform droop control on the microgrid.

[0077] Among them, a block diagram of a grid-connected control device for smart grids, such as Figure 3 shown.

[0078] Based on the same concept as the method embodiment of the present application, a grid-connected control medium for a smart grid is proposed, 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.

[0079] In summary, when there is a need for grid connection in the microgrid, the voltage amplitude and phase angle at both ends of each inverter and the impedance of the microgrid feeder are obtained at each sampling moment to provide a data basis for the subsequent dynamic adjustment of the voltage and frequency of the microgrid; the analysis window of each sampling moment is preset; the differences in the voltage amplitude and phase angle fluctuation degree at both ends of the inverter within the analysis window of each sampling moment are combined to obtain the coordination deviation at each sampling moment, which has the beneficial effect of reflecting the difference coordination of voltage and phase when the microgrid and the large grid need to be synchronized at each sampling moment; based on the change characteristics of the impedance on the microgrid feeder at each sampling moment and the adjacent sampling moment, combined with the coordination deviation at each sampling moment, the synchronization adjustment degree at each sampling moment is obtained, which reflects the degree of influence of the impedance change fluctuation on the feeder on the grid synchronization, and measures the adjustment strength of the grid synchronization control at each sampling moment; based on the synchronization adjustment degree at each sampling moment and the grid connection state of the microgrid, the adaptive proportional coefficient and adaptive integral coefficient at each sampling moment are obtained, and the PI control is used to perform droop control on the microgrid, which has the beneficial effect of being able to achieve fast synchronization control and avoid overshoot oscillation interfering with the operation stability of the microgrid and the large grid.

[0080] It should be noted that the flowcharts and block diagrams in the accompanying drawings show the possible architecture, functions and operations of the system, method and computer program product according to the embodiments of the present application. In this regard, each box in the flowchart or block diagram can represent a module, a program segment or a part of a code, and the module, a program segment or a part of a code contains one or more executable instructions for realizing the specified logical function. In some alternative implementations, the functions marked in the box can also occur in an order different from that marked in the accompanying drawings. For example, two consecutive boxes can actually be executed substantially in parallel, and they can sometimes be executed in the opposite order, which can depend on the functions involved. In the description corresponding to the flowchart and block diagram in the accompanying drawings, the operations or steps corresponding to different boxes can also occur in an order different from that disclosed in the description, and sometimes there is no specific order between different operations or steps. For example, two consecutive operations or steps can actually be executed substantially in parallel, and they can sometimes be executed in the opposite order, which can depend on the functions involved. Each block in the block diagrams and / or flowcharts, and combinations of blocks in the block diagrams and / or flowcharts, may be implemented by a dedicated hardware-based system that performs the specified functions or actions, or may be implemented by a combination of dedicated hardware and computer instructions.

[0081] The above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present application, and should all be included in the protection scope of the present application.

Claims

1. A grid connection control method for a smart grid, characterized in that: The method comprises the following steps: When the microgrid has a grid-connected demand, the voltage amplitude and phase angle at both ends of each inverter and the impedance of the microgrid feeder are obtained at each sampling moment; Preset the analysis window of each sampling moment; comprehensively analyze the differences in the voltage amplitude and phase angle fluctuation degree at both ends of the inverter within the analysis window of each sampling moment to obtain the coordinated deviation of each sampling moment; Based on the impedance variation characteristics of the microgrid feeder at each sampling moment and the adjacent sampling moments, combined with the coordination deviation at each sampling moment, the synchronization adjustment degree at each sampling moment is obtained; Based on the synchronization adjustment degree at each sampling moment and the grid-connected state of the microgrid, the adaptive proportional coefficient and the adaptive integral coefficient at each sampling moment are obtained, and PI control is used to perform droop control on the microgrid.

2. A smart grid-oriented grid connection control method as claimed in claim 1, characterized in that: The two ends of the inverter include a microgrid end and a large grid end.

3. A smart grid-oriented grid connection control method as claimed in claim 2, characterized in that: The coordinated deviation at each sampling moment is obtained as follows: According to the difference of voltage amplitude fluctuation degree between the inverter microgrid end and the large grid end in the analysis window at each sampling moment, the double-terminal stability at each sampling moment is obtained; A first sequence consisting of all voltage phase angles at the inverter microgrid end and a second sequence consisting of all voltage phase angles at the large grid end in the analysis window at each sampling moment are obtained respectively; based on the distance measurement between the first sequence and the second sequence and the negative correlation mapping result of the two-end stability, the coordinated deviation at each sampling moment is obtained.

4. A smart grid-oriented grid connection control method as claimed in claim 3, characterized in that: The double-end stability at each sampling moment is obtained as follows: The negative correlation mapping result after merging the fluctuation degree of all voltage amplitudes at the inverter microgrid end and the large grid end in the analysis window at each sampling moment is taken as the double-terminal stability at each sampling moment.

5. A smart grid-oriented grid connection control method as claimed in claim 1, characterized in that: The synchronization adjustment degree of each sampling moment is obtained as follows: Obtain the feeder interference degree at each sampling moment according to the impedance difference between each sampling moment and the adjacent sampling moments; The normalized value of the fusion of the coordination deviation and feeder interference degree of each microgrid at each sampling moment is used as the synchronization adjustment degree at each sampling moment.

6. A smart grid-oriented grid connection control method as claimed in claim 5, characterized in that: The feeder interference degree at each sampling moment is specifically the modulus of the difference between the feeder impedance at each sampling moment and the feeder impedance at the previous sampling moment.

7. A smart grid-oriented grid connection control method according to claim 1, characterized in that: The process of obtaining the adaptive proportional coefficient and the adaptive integral coefficient at each sampling moment includes: Based on the grid-connected state of the microgrid at each sampling moment, the grid-connected state control coefficient at each sampling moment is obtained, which is recorded as ε; The formulas for the adaptive proportional coefficient and adaptive integral coefficient at each sampling moment are: In the formula, K p , K I Respectively represent the adaptive proportional coefficient and adaptive integral coefficient at each sampling moment, They represent the initial proportional coefficient and the initial integral coefficient respectively, η represents the synchronization adjustment degree at the current sampling moment, ΔP and ΔI represent the preset proportional distance and the preset integral distance respectively.

8. A smart grid-oriented grid connection control method as claimed in claim 7, characterized in that: The specific process of obtaining the grid-connected state control coefficient is as follows: When the microgrid is not connected to the large grid, the first preset value is used as the grid-connected state control coefficient at the corresponding sampling moment; otherwise, the second preset value is used as the grid-connected state control coefficient at the corresponding sampling moment, wherein the first preset value is greater than the second preset value.

9. A grid-connected control device for a smart grid, characterized in that: include: Grid-connected data acquisition module: used to obtain the voltage amplitude and phase angle at both ends of each inverter and the impedance of the microgrid feeder at each sampling moment when the microgrid has a grid-connected demand; Grid-connected data analysis module: used to preset the analysis window of each sampling moment; comprehensively consider the differences in the voltage amplitude and phase angle fluctuation degree at both ends of the inverter within the analysis window of each sampling moment, and obtain the coordination deviation of each sampling moment; based on the impedance variation characteristics on the microgrid feeder at each sampling moment and the adjacent sampling moment, combined with the coordination deviation of each sampling moment, obtain the synchronization adjustment degree of each sampling moment; Grid-connected control module: used to obtain the adaptive proportional coefficient and adaptive integral coefficient at each sampling moment based on the synchronization adjustment degree at each sampling moment and the grid-connected state of the microgrid, and use PI control to perform droop control on the microgrid.

10. A grid-connected control medium for a smart grid, 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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