A method and system for detecting grid stability after grid-connection of an output-uncertain power supply

Abstract

The present application belongs to the field of electric power, and particularly relates to a method and system for detecting the stability of a power grid after a power source with uncertain output is connected to the grid. The method comprises obtaining first output data of at least one grid-connected power source in the power grid; obtaining first time data, which includes the time from when the grid-connected power source is connected to the power grid to when the power grid achieves transient stability; and calculating a grid stability value based on the first output data and the first time data. The first output data of at least one grid-connected power source is obtained as the data for judging the stability of the power grid, which is easy to obtain and requires a small amount of data to be processed. The first time data is obtained, which can determine an appropriate time to judge the influence of the grid-connected power source on the power grid. The grid stability value can be determined based on the first output data and the first time data to evaluate the stability of the power grid.

Description

Technical Field

[0001] This invention belongs to the field of power, and in particular relates to a method and system for detecting the stability of the power grid after a power source with uncertain output is connected to the grid. Background Technology

[0002] Electricity, as an essential energy source for the operation of society, is supplied to specific areas through the power grid. Social development is a dynamic process; therefore, the construction and operation of the power grid are not static.

[0003] As electricity demand increases or new power sources are added, the newly connected power sources will impact the operation of the power grid itself. This change will not only affect the new power sources but may also affect other parts of the grid. Therefore, when power grid expansion occurs, it is necessary to monitor the grid and determine the impact of the new power sources on it.

[0004] Current detection technologies primarily focus on the power grid itself, requiring extensive data acquisition equipment and generating massive amounts of data that are difficult to process. Summary of the Invention

[0005] To address or improve the aforementioned problems, this invention provides a method and system for detecting grid stability after a power source with uncertain output is connected to the grid. The specific technical solution is as follows:

[0006] This invention provides a method for detecting grid stability after a power source with uncertain output is connected to the grid, comprising: acquiring first output data of at least one grid-connected power source in the grid; acquiring first time data, the first time data including the time from when the grid-connected power source is connected to the grid to when the grid achieves transient stability; and calculating a grid stability value based on the first output data and the first time data.

[0007] Preferably, the step of calculating the power grid stability value based on the first output data and the first time data includes: determining a first time period in which the maximum rate of change occurs from the output data, with a first time length; filtering second output data including the first time period from the output data, with a second time length; and calculating the power grid stability value based on the second output data and the first time data.

[0008] Preferably, the output data includes a first output sequence obtained by processing the output curve based on a preset time interval; correspondingly, the power grid stability value is calculated based on the first output sequence and the first time data.

[0009] Preferably, the grid stability detection method after the power source with uncertain output is connected to the grid includes: processing the first output sequence by multiplying coefficients to obtain a second output sequence; correspondingly, calculating the grid stability value based on the second output sequence and the first time data.

[0010] Preferably, the first time data includes: the time during which the output change rate exceeds a first threshold after the grid-connected power source is connected to the power grid; and / or, the time during which the output value changes more than a second threshold after the grid-connected power source is connected to the power grid.

[0011] Preferably, before acquiring the first output data of at least one grid-connected power source in the power grid, the method further includes: marking grid-connected power sources with uncertain output; correspondingly, after calculating the power grid stability value based on the first output data and the first time data, the method further includes: filtering the grid-connected power sources with uncertain output based on the power grid stability value.

[0012] Preferably, the first output data includes active power output and reactive power output; correspondingly, the step of calculating the power grid stability value based on the first output data and the first time data includes: calculating the corresponding power grid stability value based on the active power output and / or reactive power output and the first time data.

[0013] Preferably, the power grid stability value is calculated based on the first output value and the first time using commercial data processing software.

[0014] Preferably, the grid-connected power source is a power source based on wind energy and / or solar energy.

[0015] This invention provides a grid stability detection system after a power source with uncertain output is connected to the grid, comprising: a data acquisition unit for acquiring first output data of at least one grid-connected power source in the grid; a data recording unit for acquiring first time data, the first time data including the time from when the grid-connected power source connects to the grid to when the grid achieves transient stability; and a data processing unit for calculating a grid stability value based on the first output data and the first time data.

[0016] The beneficial effects of this invention are as follows: by acquiring the first output data of at least one grid-connected power source as data for judging grid stability, the acquisition difficulty is low and the amount of data to be processed is small; by acquiring the first time data, it is possible to determine the appropriate time to judge the impact of the grid-connected power source on the grid; and by using the first output data and the first time data, it is possible to determine the grid stability value to assess the degree of grid stability. Attached Figure Description

[0017] Figure 1This is a schematic diagram of the grid stability detection method after the power source with uncertain output is connected to the grid according to the present invention;

[0018] Figure 2 This is a schematic diagram of the power grid stability detection system after the uncertain output power source is connected to the grid according to the present invention.

[0019] Explanation of key figure labels:

[0020] 1-Data acquisition unit, 2-Data recording unit, 3-Data processing unit. Detailed Implementation

[0021] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] It should be understood that, when used in this specification and the appended claims, the terms "comprising" and "including" indicate the presence of the described features, integrals, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or collections thereof.

[0023] It should also be understood that the terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the invention. As used in this specification and the appended claims, the singular forms “a,” “an,” and “the” are intended to include the plural forms unless the context clearly indicates otherwise.

[0024] It should also be further understood that the term "and / or" as used in this specification and the appended claims refers to any combination of one or more of the associated listed items and all possible combinations, and includes such combinations.

[0025] To address or improve the problem of power grid stability monitoring, the following proposals are put forward: Figure 1 The method for detecting grid stability after a power source with uncertain output is shown includes:

[0026] S1. Obtain the first output data of at least one grid-connected power source in the power grid;

[0027] S2. Acquire first-time data, which includes the time from when the grid-connected power source connects to the grid to when the grid achieves transient stability.

[0028] S3. Calculate the power grid stability value based on the first output data and the first time data.

[0029] A power grid generally consists of power sources, voltage transformation equipment, transmission lines, and electrical loads. Power sources can be remote power plants that transmit electricity to the local area via ultra-high-voltage circuits; alternatively, they can be local power plants or generators. Voltage transformation equipment, typically substations, adjusts the output voltage according to actual needs. Transmission lines, in the physical sense, comprise the power grid, consisting of power lines, poles, and various auxiliary components. Electricity from distribution substations is distributed to various electrical loads via these transmission lines. Electrical loads are the terminals of electricity consumption, including factory equipment and residential appliances. Both power sources and voltage transformation equipment, being voltage output terminals, can be classified as power sources.

[0030] Large, resource-rich cities can easily secure large, stable power sources. Even so, these cities often experience various unusual electricity demands, such as factories requiring specific voltages or needing backup power. Smaller cities, on the other hand, may experience aging power infrastructure or urban development leading to abnormal or insufficient power output, necessitating replacement or addition of power sources. Due to the complexity of power grid mechanisms, in practice, new power sources rarely adapt perfectly to the grid upon connection. Instead, numerous problems arise, such as the impact of newly added power sources on the grid itself, and the grid in turn affecting the newly added power sources. In practice, large power sources are far more adaptable to anomalies than small ones. Therefore, even if the grid experiences anomalies, large power sources tend to operate relatively stably. Conversely, small power sources may become unstable due to grid anomalies. If one believes that as long as large power sources remain normal, ignoring the impact of grid anomalies on small power sources is acceptable, then the instability of small power sources due to these anomalies can affect other small power sources and even large power sources, ultimately leading to new anomalies in the entire power grid.

[0031] In Chinese regulations, standards, and documents, the stability of power systems is generally classified into the following two categories:

[0032] 1) Static stability: Static stability of a power system mainly refers to the ability of a power system to maintain its original state or continue to operate in a state close to its original state after being subjected to a small disturbance. This operating condition is called static stability or small disturbance stability.

[0033] 2) Transient stability: If a power system reaches a state different from the original state after a disturbance, but can still operate stably, this operating state is called transient stability.

[0034] Generally speaking, if the conditions for transient stability are met, the conditions for static stability are also met. Therefore, maintaining static stability is a prerequisite for transient stability. In practice, maintaining a certain static stability margin can provide a buffer for transient stability in the event of a severe fault. Once the grid-connected power source is connected to the grid, and the grid achieves a stable state—that is, after the aforementioned static or transient stability—the grid's operation will not face catastrophic problems.

[0035] The output of green new energy sources, primarily wind and solar power, is random and therefore uncertain. Grid-connected power sources operate by outputting electricity, and output value is a parameter used to specifically assess the power output capability of a power source, including electromagnetic power, mechanical power, frequency, period, voltage, and current.

[0036] In the initial stage of grid connection, the power source interacts with the grid and will not immediately operate at its rated output. Therefore, the output of the power source is in an uncertain state, requiring interaction between the power source and the grid until a stable state is reached. This period is considered the first-time data. By acquiring the output values ​​of the power source during and after the formation of a stable state, we obtain the first-time output data. Based on this first-time data, we filter the first-time output data for specific time periods and process it according to a set formula to obtain a grid stability value used to evaluate the stability of the grid after the power source is connected.

[0037] The step of calculating the power grid stability value based on the first output data and the first time data includes: determining a first time period in which the maximum rate of change occurs from the output data, using a first time length; filtering second output data including the first time period from the output data, using a second time length; and calculating the power grid stability value based on the second output data and the first time data.

[0038] Power systems inherently prioritize stability and are designed to mitigate anomalies. Furthermore, they are particularly sensitive to sudden changes. Therefore, when analyzing the stability of power grid operation, data exhibiting the greatest variation can be selected as the primary analytical material. For instance, the highest rate of change in output data poses the greatest threat to grid stability.

[0039] To determine the rate of change, it's necessary to identify the changing value and the time period of the change. A first time length, such as 1 hour, 1 day, or 1 week, can be set as a time frame. The difference between the lowest and highest values ​​within the time frame is taken as the changing value, the time frame length as the time period of the change, and the ratio of the changing value to the time period as the rate of change. The largest rate of change is determined among all output data, and the time frame including this largest rate of change is the first time period. After determining the largest rate of change, it's necessary to select and add continuous data. Analyzing why there is a largest rate of change requires considering nearby time points, not just a single isolated time point. Therefore, a second time length, not less than the first time length, is set as a new time frame, including the first time period. This second time frame is used to determine the anomaly occurrence point and nearby time points within the continuous time frame. Determining the second time length and the corresponding output data allows for analysis of the cause of the largest rate of change.

[0040] The output data includes a first output sequence obtained by processing the output curve based on a preset time interval; correspondingly, the power grid stability value is calculated based on the first output sequence and the first time data.

[0041] The working mechanism of a power grid is complex, and in many cases, the changes occurring at a particular moment cannot be perfectly explained by explicit theories and formulas. Therefore, compared to continuous data curves, data sequences can be better explained by existing theories and calculation formulas. Even if the explanation is not perfect, it can still provide some assistance in solving problems in practice.

[0042] Record the output of one or more power sources with uncertain output within a certain time period, i.e., grid-connected power sources, and convert the corresponding output curves into a discrete time sequence. The time interval of the sequence can be several milliseconds, seconds, minutes, hours, etc., as needed.

[0043] Using commercial data processing software such as BPA, PSASP, PSS / E, and MATLAB, at the point of connection of power sources with uncertain output, the output in the sequence is read in the time order listed in the sequence to calculate the transient process of the power grid and obtain the judgment results of frequency and power angle stability. Parameters such as frequency and power angle stability are commonly used parameters for evaluating the state of the power grid. Through these parameters or the values ​​calculated based on these parameters, the state of the regional power grid can be evaluated, that is, the power grid stability value.

[0044] The method for detecting grid stability after a power source with uncertain output is connected to the grid includes: processing the first output sequence by multiplying coefficients to obtain a second output sequence; correspondingly, calculating the grid stability value based on the second output sequence and the first time data.

[0045] In the actual calculation of power grid stability values, due to factors such as errors in the collected data, calculation errors in industry operations, and computing power limitations, the raw data may undergo certain preprocessing. Multiplying coefficients to process the first output sequence can improve the efficiency and effectiveness of the calculation. Therefore, the first output sequence can be processed by multiplying coefficients to obtain the second output sequence, and then the second output sequence can be used to calculate the corresponding power grid stability value.

[0046] The first time data includes: the time during which the output change rate of the grid-connected power source exceeds a first threshold after it is connected to the power grid; and / or the time during which the output value changes more than a second threshold after the grid-connected power source is connected to the power grid.

[0047] Before obtaining the first output data of at least one grid-connected power source in the power grid, the method further includes: marking grid-connected power sources with uncertain output; correspondingly, after calculating the power grid stability value based on the first output data and the first time data, the method further includes: filtering the grid-connected power sources with uncertain output based on the power grid stability value.

[0048] The first output data includes active power output and reactive power output; correspondingly, the step of calculating the power grid stability value based on the first output data and the first time data includes: calculating the corresponding power grid stability value based on the active power output and / or reactive power output and the first time data.

[0049] Active power output is the power output of a power source, while reactive power output is the power generated by the power source itself during operation that is not output to the outside world. The corresponding grid stability value is calculated based on the difference between the two, which can be used to judge its ability to output useful power to the outside world, as well as the reactive power generated by the power source when it is within the grid.

[0050] The power grid stability value is calculated based on the first output value and the first time using commercial data processing software.

[0051] The grid-connected power source is a power source based on wind energy and / or solar energy.

[0052] The grid-connected power source is a power source with uncertain output, including new energy sources such as wind power and photovoltaic power, as well as other energy sources affected by the environment, such as tidal power generation; even relatively mature thermal power and hydropower may have unstable output due to various reasons, and in this case, such thermal power and hydropower power sources also belong to power sources with uncertain output.

[0053] This invention provides, for example Figure 2 The system shown is a grid stability detection system after a power source with uncertain output is connected to the grid. It includes: a data acquisition unit 1, used to acquire first output data of at least one grid-connected power source in the grid; a data recording unit 2, used to acquire first time data, which includes the time from when the grid-connected power source is connected to the grid to when the grid achieves transient stability; and a data processing unit 3, used to calculate a grid stability value based on the first output data and the first time data.

[0054] Those skilled in the art will recognize that the units of the various examples described in connection with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of both. To clearly illustrate the interchangeability of hardware and software, the components of the various examples have been generally described in terms of functionality in the foregoing description. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementations should not be considered beyond the scope of the invention.

[0055] In the embodiments provided in this application, it should be understood that the division of units is only a logical functional division. In actual implementation, there may be other division methods, such as multiple units can be combined into one unit, one unit can be split into multiple units, or some features can be ignored.

[0056] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention, and they should all be covered within the scope of the claims and specification of the present invention.

Claims

1. A method for detecting grid stability after a power source with uncertain output is connected to the grid, characterized in that, include: The output data of at least one grid-connected power source in the power grid is acquired, and the output data is processed into a first output sequence based on a preset time interval. Acquire first-time data, which includes the time from when the grid-connected power source connects to the power grid to when the power grid achieves transient stability. Based on commercial data processing software, the transient process of the power grid is calculated according to the first output sequence and the first time data to obtain a power grid stability value. The power grid stability value is a value calculated based on the judgment result of frequency and / or power angle stability. The output data includes a first output sequence obtained by processing the output curve based on a preset time interval. Correspondingly, the power grid stability value is calculated according to the first output sequence and the first time data. The calculation of the power grid stability value based on the first output data and the first time data includes: The first time period in which the maximum rate of change occurs is determined from the output data, using a first time length; Using a second time length, a second output sequence including the first time period is selected from the output data; this includes: processing the first output sequence by multiplying coefficients to obtain the second output sequence; The power grid stability value is calculated based on the second output sequence and the first time data.

2. The method for detecting grid stability after grid connection of a power source with uncertain output according to claim 1, characterized in that, The first time data includes: The time during which the output change rate of the grid-connected power source exceeds the first threshold after it is connected to the power grid; And / or, the time during which the output value of the grid-connected power source changes more than the second threshold after it is connected to the power grid.

3. The method for detecting grid stability after grid connection of a power source with uncertain output according to claim 2, characterized in that, Before acquiring the first output data of at least one grid-connected power source within the power grid, the method further includes: Mark grid-connected power sources with uncertain output; Correspondingly, after calculating the power grid stability value based on the first output data and the first time data, the method further includes: The grid-connected power sources with uncertain output are selected based on the grid stability values.

4. The method for detecting grid stability after grid connection of a power source with uncertain output according to claim 3, characterized in that, The first output data includes active power output and reactive power output; Correspondingly, the step of calculating the power grid stability value based on the first output data and the first time data includes: The corresponding grid stability value is calculated based on the active power output and / or reactive power output, and the first time data.

5. The method for detecting grid stability after grid connection of a power source with uncertain output according to claim 4, characterized in that, The power grid stability value is calculated based on the first output value and the first time using commercial data processing software.

6. The method for detecting grid stability after grid connection of a power source with uncertain output according to claim 5, characterized in that, The grid-connected power source is a power source based on wind energy and / or solar energy.

7. A grid stability detection system after a power source with uncertain output is connected to the grid, characterized in that, The method described in any one of claims 1-6 includes: A data acquisition unit is used to acquire the output data of at least one grid-connected power source in the power grid, and process the output data into a first output sequence based on a preset time interval. The data recording unit is used to acquire first time data, which includes the time from when the grid-connected power source connects to the power grid to when the power grid achieves transient stability. The data processing unit is used to calculate the transient process of the power grid based on the first output sequence and the first time data using commercial data processing software, and to obtain a power grid stability value, wherein the power grid stability value is a value calculated based on the judgment result of frequency and / or power angle stability.

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