Power grid partition protection constant value intelligent switching system based on correlation measurement

Abstract

The invention relates to the technical field of power distribution network relay protection, and discloses a power grid partition protection constant value intelligent switching system based on correlation measurement, and the system comprises a correlation measurement module which is used for calculating the correlation coefficient among the wind speed Vw, the irradiance Ir and the load PL according to the correlation among the wind speed Vw, the irradiance Ir and the load PL; the expert system module is used for establishing an optimization efficiency function fopt by combining the correlation measurement result with the action time of the power grid, and constructing an expert system; a topology adjustment module; according to the method, the protection constant value of the power grid can be automatically adjusted based on the real-time environment data (such as wind speed, irradiance and temperature) and the power grid operation parameters, so that a protection system can more accurately cope with changes of various factors in the power grid, and the power grid protection efficiency and reliability are improved. Especially in an electric power system with a high new energy occupation ratio, novel power supply characteristics which cannot be handled by a traditional protection method can be effectively compensated, and the stability and the safety of a power grid are ensured.

Description

Technical Field

[0001] The invention relates to the technical field of distribution network relay protection, and in particular to a power grid partition protection fixed value intelligent switching system based on correlation measurement. Background Art

[0002] With the widespread application of new energy in the power system, especially the large-scale access of distributed power sources such as wind power and photovoltaics, the operation and protection mechanism of traditional distribution networks are facing unprecedented challenges. The access of a high proportion of new energy power sources, especially the intermittent and volatile wind and solar resources, has brought new challenges to the operation, control and protection of traditional power systems.

[0003] The access of distributed power sources with high penetration rate, especially solar and wind power generation, will change the short-circuit characteristics of the system due to its intermittent, volatile and random characteristics, which is mainly reflected in the following aspects:

[0004] 1. The output volatility of new energy power sources makes the calculation of short-circuit current more complicated, especially when photovoltaic or wind power is connected to the grid, the short-circuit current of the system is not only affected by load changes, but also by weather factors such as light and wind speed; 2. Unlike traditional centralized generators, distributed power sources are often connected to the low-voltage distribution system, which has different impacts on the short-circuit current distribution of the power grid. Too high or too low access ratios may lead to over-estimation or under-estimation of current, affecting the action of protection devices; 3. At the same time, the dynamic relationship between distributed power sources and loads, especially changes in weather factors such as wind speed, light intensity, and temperature, will directly affect the operating characteristics of the power grid. This dynamic relationship makes it difficult for traditional static protection settings to adapt to rapidly changing system requirements.

[0005] The setting of distribution network protection constants is the basis for ensuring the safe operation of the distribution network. It directly affects key functions such as short-circuit protection, overload protection, and equipment fault isolation of the distribution network. Traditional protection constant setting methods usually rely on static calculations or empirical settings, which are difficult to cope with the impact of dynamically changing system loads, power access, and environmental factors. In the context of the access of new energy power sources, the operating characteristics of the distribution network have changed significantly. The traditional constant setting method cannot adapt to the time-varying load and power conditions. There are problems such as inaccurate constant setting, delayed protection action or false action, which leads to unstable system protection functions. In some cases, the fault cannot be removed in time, endangering the safety of power equipment and systems.

[0006] Based on this, this paper proposes a grid partition protection setting intelligent switching system based on correlation measurement, aiming to improve the grid protection efficiency and reliability when multiple distributed power sources are connected in distribution networks and microgrids. The system realizes intelligent adjustment of protection setting and protection strategy adopted by setting distribution network partitions and combining correlation measurement between grid operation parameters (such as wind speed, irradiance, load, etc.) to cope with dynamic changes in the grid operation environment. Summary of the invention

[0007] The purpose of the present invention is to provide a power grid partition protection setting intelligent switching system based on correlation measurement to solve the problems raised in the above background technology.

[0008] In order to achieve the above object, the present invention provides the following technical solution: a power grid partition protection fixed value intelligent switching system based on correlation measurement, comprising:

[0009] Correlation measurement module: used to measure the wind speed V w , irradiance I r , load P L The relationship between them is calculated, and the correlation coefficient between them is calculated;

[0010] There is a negative correlation between wind speed and irradiance and load, and a positive correlation between irradiance and load.

[0011] Expert system module: Combine the correlation measurement results and the action time of the power grid to establish the optimization efficiency function f opt , and build an expert system to optimize the efficiency function as follows:

[0012]

[0013] Where: T i Indicates the protection action time, w i is the weight coefficient, λ is the penalty factor, S j Indicates the current setting value, S set Indicates the target setting value, and achieves the best overall efficiency by adjusting the time coordination between the protection action time and the power grid state and optimizing the setting value;

[0014] Topology adjustment module: When the system topology or load conditions change, the topology adjustment module automatically senses the node voltage V i , load P i , reactive power Q i Parameters, automatically adjust the protection setting value S according to the reasoning results of the expert system set , to meet the protection needs of the power grid during dynamic operation.

[0015] The correlation coefficient calculation formula is:

[0016]

[0017] Where: xy represents the correlation between variables x and y, and represents the mean of x and y, where the wind speed V can be used w , irradiance I r , load P L .

[0018] It also includes: a sub-region selection module, which is used to divide the power grid into different regions and select protection settings. The regions include:

[0019] AC area: For the AC area, configure AC overcurrent protection, overvoltage protection, AC connection line grounding, starting circuit thermal overload, neutral point thermal overload, and frequency protection. The setting value S ac for:

[0020] S ac =f(V rms ,I rms ,T set ,f set )

[0021] Among them, V rms , I rms are the effective values ​​of voltage and current respectively, T set , f set They are the setting values ​​of protection action time and frequency respectively;

[0022] DC area: For the DC area, configure DC low voltage overcurrent, DC overvoltage, DC low voltage, DC field grounding overcurrent, AC and DC line contact protection, and its setting value S dc for:

[0023] S dc =g(V dc ,I dc ,T set )

[0024] Among them, V dc , I dc are DC voltage and current respectively;

[0025] Conversion area: For the converter area, voltage protection and current protection are configured, and the voltage protection setting value is S v , the current protection setting is S i , its automatic switching is based on the following logic:

[0026]

[0027] Among them, Zeq is the equivalent impedance, Z th is the protection switching threshold.

[0028] Among them, the protection setting selection module of the commutation area can automatically switch between voltage protection and current protection, and the switching is based on the equivalent impedance Z obtained after the grid parameter identification. eq :

[0029]

[0030] Among them, V means , I means are the voltage and current measurements, respectively;

[0031] The calculation of equivalent impedance is used to monitor the instantaneous state of the power grid. When the equivalent impedance reaches a certain threshold value Z th When the voltage protection is on, the system automatically switches between voltage protection and current protection to improve the reliability of protection action and the safety of grid operation;

[0032] The protection setting selection module of the commutation area can switch to the current protection Si first when judging that the commutation station is overloaded or in other abnormal conditions based on the equivalent impedance, so as to avoid equipment damage caused by voltage fluctuations and give priority to protecting the safety of the commutation equipment.

[0034] Among them, it also includes: an optimization efficiency function construction module, which optimizes the overall protection efficiency by calculating the action time coordination between different protection settings and the power grid state, so that the action time of the protection device matches the electrical state change of the power grid, thereby achieving the optimal protection effect of the power grid;

[0035] The optimization efficiency function also takes into account the sensitivity and reliability of protection, and its objective function is as follows:

[0036]

[0037] Among them, α, β are adjustment coefficients, R sen Sensitivity requirements for protection.

[0038] Among them, the correlation measurement module is further used to monitor the wind speed V in real time w , irradiance I r 、Load P L Parameters, through the mining of historical data to establish the correlation model between multiple variables, the correlation matrix R is expressed as:

[0039]

[0040] in, are the correlation coefficients among wind speed, load and irradiance, respectively.

[0041] Among them, considering that the topological structure of the distribution network may change, which brings difficulties to the setting of the protection value, it also includes: protection vulnerability index, which is used to represent the protection reliability of the entire distribution network, and calculates the line weight matrix W:

[0042]

[0043] Among them, w ij is the line impedance modulus;

[0044] Furthermore, the node importance is calculated And the importance of the line

[0045]

[0046] in, B is the normalized value considering load uncertainty. i is the set of directly connected edges of the node, is the shortest path between nodes;

[0047] The fewer direct edges The smaller it is, the greater the line impedance The larger the value, the more distant the node is from the network. Therefore, the node vulnerability D(i) is defined as:

[0048]

[0049] Furthermore, the overall distribution network protection vulnerability S is calculated nv :

[0050]

[0051] Among them, D full (i) is the comprehensive node vulnerability of the fully connected network.

[0052] Among them, the topology adjustment module can automatically sense the changes in nodes when the system topology changes, and combine with the expert system reasoning to quickly generate updated protection settings to ensure the reliability and safety of the power grid.

[0053] It also includes: an action time coordination module, which is used to ensure that there is a reasonable time gradient between the action times of the protection devices in each area when a power grid fails, so as to ensure the effectiveness of graded removal, thereby improving the stability of the system and the reliability of power supply.

[0054] The switching system is applied to the distribution network connected to wind power and photovoltaic new energy, and realizes efficient operation of the power grid and rapid isolation of faults through real-time monitoring and intelligent protection fixed value switching.

[0055] Compared with the prior art, the present invention has the following beneficial effects:

[0056] 1. The present invention can automatically adjust the protection setting of the power grid based on real-time environmental data (such as wind speed, irradiance, temperature) and power grid operation parameters, so that the protection system can more accurately respond to changes in various factors in the power grid, thereby improving the efficiency and reliability of power grid protection. Especially in power systems with a high proportion of new energy, it can effectively compensate for the characteristics of new power sources that traditional protection methods cannot cope with, ensuring the stability and security of the power grid.

[0057] 2. The grid zoning protection strategy adopted by the present invention can implement differentiated protection setting configuration according to the characteristics of different areas of the grid. By dividing the grid into different areas such as AC area, DC area and commutation area, the protection setting can be optimized in a targeted manner. Different protection strategies are set according to the electrical characteristics and equipment operating conditions of different areas to reduce unnecessary false operations or protection failures.

[0058] 3. The present invention has made intelligent design for the switching between voltage protection and current protection in the commutation area. Combining the voltage and current fluctuation characteristics, the system can dynamically switch the appropriate protection mode according to the voltage and current fluctuation conditions detected in real time. For example, when the current fluctuation is large, the system can automatically switch from the voltage protection mode to the overcurrent protection mode, further improving the protection capability of the power grid under special circumstances and preventing electrical equipment from being damaged under abnormal conditions.

[0059] 4. The present invention reduces the reliance on manual setting and adjustment of protection settings by applying intelligent algorithms. The system can automatically judge and adjust the protection settings based on real-time monitored data, thereby reducing manual intervention and human errors and optimizing the system's operation and maintenance management. BRIEF DESCRIPTION OF THE DRAWINGS

[0060] Figure 1 It is a block diagram of the expert system of the present invention;

[0061] Figure 2 This is a schematic diagram of the structure of the present invention connected to a power distribution network. DETAILED DESCRIPTION

[0062] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0063] In order to cope with the problem that traditional static analysis and empirical setting methods of protection setting are difficult to cope with the complex dynamic changes of distribution networks under the access of high proportion of distributed power sources, this paper proposes a grid zone protection setting intelligent switching system based on correlation measurement. By introducing multi-dimensional data such as real-time load, meteorology, and operating status, an intelligent algorithm is used to perform zone protection setting and protection strategy switching for distribution network areas, so as to cope with the complexity and variability of power systems in practical applications, provide distribution networks with more accurate and reliable protection setting solutions, and improve the safety of system operation.

[0064] See also Figure 1-2 The present invention proposes a power grid partition protection fixed value intelligent switching system based on correlation measurement.

[0065] 1. A zoning protection strategy is proposed to divide the power grid into multiple independent areas, and differentiated protection setting configuration is adopted according to the operating characteristics of different areas;

[0066] 2. Optimize the protection setting value based on multi-dimensional correlation measurement. By designing a multi-dimensional correlation measurement algorithm and combining the relationship between irradiance, wind speed and load, a comprehensive efficiency optimization function is established as the judgment basis of the expert system. According to the real-time changing system data, the optimal protection setting value configuration is derived;

[0067] 3. Aiming at the special needs of the commutation area and considering the volatility of current and voltage values, an intelligent switching mechanism for current and voltage protection is proposed. Combined with the detection of current and voltage signals, it intelligently switches to a more adaptable protection mode (for example, when the current fluctuates greatly, it switches from low voltage protection to overcurrent protection).

[0068] Specifically, it includes the following modules:

[0069] Correlation measurement module: used to measure the wind speed V w , irradiance I r , load P L The relationship between them is calculated, and the correlation coefficient between them is calculated;

[0070] There is a negative correlation between wind speed and irradiance and load, and a positive correlation between irradiance and load. The correlation coefficient calculation formula is:

[0071]

[0072] Where: xy represents the correlation between variables x and y, and represents the mean of x and y, where the wind speed V can be used w , irradiance I r , load P L ;

[0073] Expert system module: Combine the correlation measurement results and the action time of the power grid to establish the optimization efficiency function f opt , and build an expert system to optimize the efficiency function as follows:

[0074]

[0075] Where: T i Indicates the protection action time, w i is the weight coefficient, λ is the penalty factor, S j Indicates the current setting value, S set Indicates the target setting value, and achieves the best overall efficiency by adjusting the time coordination between the protection action time and the power grid state and optimizing the setting value;

[0076] Topology adjustment module: When the system topology or load conditions change, the topology adjustment module automatically senses the node voltage V i , load P i , reactive power Q i Parameters, automatically adjust the protection setting value S according to the reasoning results of the expert system set , to meet the protection needs of the power grid during dynamic operation.

[0077] It also includes: a sub-region selection module, which is used to divide the power grid into different regions and select protection settings. The regions include:

[0078] AC area: For the AC area, configure AC overcurrent protection, overvoltage protection, AC connection line grounding, starting circuit thermal overload, neutral point thermal overload, and frequency protection. The setting value S ac for:

[0079] S ac =f(V rms ,I rms ,T set ,f set )

[0080] Among them, V rms , I rms are the effective values ​​of voltage and current respectively, T set , f set They are the setting values ​​of protection action time and frequency respectively;

[0081] DC area: For the DC area, configure DC low voltage overcurrent, DC overvoltage, DC low voltage, DC field grounding overcurrent, AC and DC line contact protection, and its setting value S dc for:

[0082] S dc =g(V dc ,Idc ,T set )

[0083] Among them, V dc , I dc are DC voltage and current respectively;

[0084] Conversion area: For the converter area, voltage protection and current protection are configured, and the voltage protection setting value is S v , the current protection setting is S i , its automatic switching is based on the following logic:

[0085]

[0086] Among them, Z eq is the equivalent impedance, Z th is the protection switching threshold.

[0087] Among them, the protection setting selection module of the commutation area can automatically switch between voltage protection and current protection, and the switching is based on the equivalent impedance Z obtained after the grid parameter identification. eq :

[0088]

[0089] Among them, V means , I means are the voltage and current measurements, respectively;

[0090] The calculation of equivalent impedance is used to monitor the instantaneous state of the power grid. When the equivalent impedance reaches a certain threshold value Z th When the voltage protection is on, the system automatically switches between voltage protection and current protection to improve the reliability of protection action and the safety of grid operation;

[0091] The protection setting selection module of the commutation area can switch to the current protection Si first when judging that the commutation station is overloaded or in other abnormal conditions based on the equivalent impedance, so as to avoid equipment damage caused by voltage fluctuations and give priority to protecting the safety of the commutation equipment.

[0093] Among them, it also includes: an optimization efficiency function construction module, which optimizes the overall protection efficiency by calculating the action time coordination between different protection settings and the power grid state, so that the action time of the protection device matches the electrical state change of the power grid, thereby achieving the optimal protection effect of the power grid;

[0094] The optimization efficiency function also takes into account the sensitivity and reliability of protection, and its objective function is as follows:

[0095]

[0096] Among them, α, β are adjustment coefficients, R sen Sensitivity requirements for protection.

[0097] Among them, the correlation measurement module is further used to monitor the wind speed V in real time w , irradiance I r 、Load P L Parameters, through the mining of historical data to establish the correlation model between multiple variables, the correlation matrix R is expressed as:

[0098]

[0099] in, are the correlation coefficients among wind speed, load and irradiance, respectively.

[0100] Among them, considering that the topological structure of the distribution network may change, which brings difficulties to the setting of the protection value, it also includes: protection vulnerability index, which is used to represent the protection reliability of the entire distribution network, and calculates the line weight matrix W:

[0101]

[0102] Among them, w ij is the line impedance modulus;

[0103] Furthermore, the node importance is calculated And the importance of the line

[0104]

[0105] in, B is the normalized value considering load uncertainty. i is the set of directly connected edges of the node, is the shortest path between nodes;

[0106] The fewer direct edges The smaller it is, the greater the line impedance The larger the value, the more distant the node is from the network. Therefore, the node vulnerability D(i) is defined as:

[0107]

[0108] Furthermore, the overall distribution network protection vulnerability S is calculated nv :

[0109]

[0110] Among them, D full (i) is the comprehensive node vulnerability of the fully connected network.

[0111] Among them, the topology adjustment module can automatically sense the changes in nodes when the system topology changes, and combine with the expert system reasoning to quickly generate updated protection settings to ensure the reliability and safety of the power grid.

[0112] It also includes: an action time coordination module, which is used to ensure that there is a reasonable time gradient between the action times of the protection devices in each area when a power grid fails, so as to ensure the effectiveness of graded removal, thereby improving the stability of the system and the reliability of power supply.

[0113] Among them, the switching system has a self-learning function. By continuously accumulating power grid operation data and fault data, optimizing the correlation measurement model and the inference rules of the expert system, it can adapt to the ever-changing power grid operation environment and improve the accuracy and stability of intelligent switching.

[0114] The switching system is applied to the distribution network connected to wind power and photovoltaic new energy, and realizes efficient operation of the power grid and rapid isolation of faults through real-time monitoring and intelligent protection fixed value switching.

[0115] In summary, the present invention can automatically adjust the protection setting of the power grid based on real-time environmental data (such as wind speed, irradiance, temperature) and power grid operation parameters, so that the protection system can more accurately respond to changes in various factors in the power grid, thereby improving the efficiency and reliability of power grid protection. Especially in power systems with a high proportion of new energy, it can effectively compensate for the characteristics of new power sources that traditional protection methods cannot cope with, ensuring the stability and security of the power grid.

[0116] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A power grid partition protection fixed value intelligent switching system based on correlation measurement, characterized in that: include: Correlation measurement module: used to measure the wind speed V w , irradiance I r , load P L The relationship between them is calculated, and the correlation coefficient between them is calculated; There is a negative correlation between wind speed and irradiance and load, and a positive correlation between irradiance and load. Expert system module: Combine the correlation measurement results with the action time of the power grid to establish the optimization efficiency function f opt , and build an expert system to optimize the efficiency function as follows: Where: T i Indicates the protection action time, w i is the weight coefficient, λ is the penalty factor, S j Indicates the current setting value, S set Indicates the target setting value, and achieves the best overall efficiency by adjusting the time coordination between the protection action time and the power grid state and optimizing the setting value; Topology adjustment module: When the system topology or load conditions change, the topology adjustment module automatically senses the node voltage V i , load P i , reactive power Q i Parameters, automatically adjust the protection setting value S according to the reasoning results of the expert system set , to meet the protection needs of the power grid during dynamic operation.

2. According to claim 1, a power grid partition protection fixed value intelligent switching system based on correlation measurement is characterized in that: The correlation coefficient calculation formula is: Where: xy represents the correlation between variables x and y, and represents the mean of x and y, where the wind speed V can be used w , irradiance I r , load P L .

3. The power grid partition protection fixed value intelligent switching system based on correlation measurement according to claim 2 is characterized in that: Also includes: The regional selection module is used to divide the power grid into different areas and select protection settings. The areas include: AC area: For the AC area, configure AC overcurrent protection, overvoltage protection, AC connection line grounding, starting circuit thermal overload, neutral point thermal overload, and frequency protection. The setting value S ac for: S ac =f(V rms ,I rms ,T set ,f set ) Among them, V rms , I rms are the effective values ​​of voltage and current respectively, T set , f set They are the setting values ​​of protection action time and frequency respectively; DC area: For the DC area, configure DC low voltage overcurrent, DC overvoltage, DC low voltage, DC field grounding overcurrent, AC and DC line contact protection, and its setting value S dc for: S dc =g(V dc ,I dc ,T set ) Among them, V dc , I dc are DC voltage and current respectively; Conversion area: For the converter area, voltage protection and current protection are configured, and the voltage protection setting value is S v , the current protection setting is S i , its automatic switching is based on the following logic: Among them, Z eq is the equivalent impedance, Z th is the protection switching threshold.

4. The power grid partition protection fixed value intelligent switching system based on correlation measurement according to claim 3 is characterized by: The protection setting selection module of the commutation area can automatically switch between voltage protection and current protection. The switching is based on the equivalent impedance Z obtained after the grid parameters are identified. eq : Among them, V means , I means are the voltage and current measurements, respectively; The calculation of equivalent impedance is used to monitor the instantaneous state of the power grid. When the equivalent impedance reaches a certain threshold value Z th When the voltage protection is on, the system automatically switches between voltage protection and current protection to improve the reliability of protection action and the safety of grid operation; The protection setting selection module of the commutation area can switch to the current protection Si first when judging that the commutation station is overloaded or in other abnormal conditions based on the equivalent impedance, so as to avoid equipment damage caused by voltage fluctuations and give priority to protecting the safety of the commutation equipment.

5. A power grid partition protection fixed value intelligent switching system based on correlation measurement according to claim 4, characterized in that: Also includes: Optimizing efficiency function building module: The optimizing efficiency function building module optimizes the overall protection efficiency by calculating the coordination of the action time between different protection settings and the power grid state, so that the action time of the protection device matches the change of the electrical state of the power grid, thereby achieving the optimal protection effect of the power grid; The optimization efficiency function also takes into account the sensitivity and reliability of protection, and its objective function is as follows: Among them, α, β are adjustment coefficients, R sen Sensitivity requirements for protection.

6. The power grid partition protection fixed value intelligent switching system based on correlation measurement according to claim 5 is characterized by: The correlation measurement module is further used to monitor the wind speed V in real time. w , irradiance I r 、Load P L Parameters, through the mining of historical data to establish the correlation model between multiple variables, the correlation matrix R is expressed as: in, are the correlation coefficients among wind speed, load and irradiance, respectively.

7. The power grid partition protection fixed value intelligent switching system based on correlation measurement according to claim 6 is characterized by: Considering that the topology of the distribution network may change, which brings difficulties to the setting of the protection value, it also includes: protection vulnerability index, which is used to represent the protection reliability of the entire distribution network, and calculates the line weight matrix W: Among them, w ij is the line impedance modulus; Furthermore, the node importance is calculated And the importance of the line in, B is the normalized value considering load uncertainty. i is the set of directly connected edges of the node, is the shortest path between nodes; The fewer direct edges The smaller it is, the greater the line impedance The larger the value, the more distant the node is from the network. Therefore, the node vulnerability D(i) is defined as: Furthermore, the overall distribution network protection vulnerability S is calculated nv : Among them, D full (i) is the comprehensive node vulnerability of the fully connected network.

8. The power grid partition protection fixed value intelligent switching system based on correlation measurement according to claim 7 is characterized in that: The topology adjustment module can automatically sense node changes when the system topology changes, and combine with expert system reasoning to quickly generate updated protection settings to ensure the reliability and safety of the power grid.

9. A power grid partition protection fixed value intelligent switching system based on correlation measurement according to claim 8, characterized in that: Also includes: The action time coordination module is used to ensure that there is a reasonable time gradient between the action times of the protection devices in each area when a power grid fails, so as to ensure the effectiveness of graded removal, thereby improving the stability of the system and the reliability of power supply.

10. The power grid partition protection fixed value intelligent switching system based on correlation measurement according to claim 9, characterized in that: The switching system is applied to the distribution network connected to wind power and photovoltaic new energy, and realizes efficient operation of the power grid and rapid fault isolation through real-time monitoring and intelligent protection fixed value switching.

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