An intelligent control system and method for high overload on-load voltage regulation distribution transformer based on intelligent fusion terminal

Abstract

The application discloses a high-overload on-load voltage regulation power distribution transformer intelligent regulation and control system and method based on an intelligent fusion terminal, and the system comprises an intelligent fusion terminal, an inverter power control module of a photovoltaic power generation system, an on-load voltage regulation controller of a high-overload transformer voltage regulation system and a high-overload on-load voltage regulation power distribution transformer. The application can flexibly adjust a voltage regulation strategy, avoids a fixed regulation mode in the prior art, and improves the stability of power grid voltage regulation and the service life of equipment.

Description

Technical Field

[0001] This invention relates to the field of power system measurement and detection technology, specifically to an intelligent control system and method for high overload on-load voltage regulating distribution transformers based on intelligent fusion terminals. Background Technology

[0002] Transformers, as fundamental equipment for power transmission and distribution, are a crucial component of the power system. With the large-scale integration of new energy sources, higher demands are placed on distribution transformers. Currently, high-overload distribution transformers are mainly used in high-penetration photovoltaic (PV) areas, but they currently lack on-load tap-changing technology. The main challenge lies in the need to consider the transformer's health status assessment when combining high-overload and on-load tap-changing technologies. Therefore, the following two requirements are placed on high-overload distribution transformers: firstly, the distribution transformer health diagnosis system needs to be more comprehensive; secondly, the voltage regulation strategy needs to adapt to the complex operating conditions brought about by the large-scale integration of new energy sources. Existing technologies still have two problems: firstly, the data volume of distribution transformers and PV systems is enormous and highly nonlinear and time-varying; existing data analysis methods and fault diagnosis systems cannot efficiently process this complex data, leading to a lag in the identification of potential faults. Secondly, existing regulation strategies have limitations; they cannot fully consider the transformer's health status and the output of the PV inverter during voltage regulation, resulting in slow and inflexible voltage regulation control response. Summary of the Invention

[0003] Purpose of the invention: The purpose of this invention is to provide an intelligent control system and method for on-load tap changer distribution transformers under high overload conditions based on an intelligent fusion terminal. The system is uniformly processed and controlled by the fusion terminal, and combined with the health status of the high overload distribution transformer itself, it controls the on-load tap changer and photovoltaic inverter under different voltage fluctuations in the complex operating conditions of the distribution transformer, thereby solving the problems existing in the background technology.

[0004] Technical Solution: The present invention discloses an intelligent control system for a high overload on-load tap-changing distribution transformer based on an intelligent integrated terminal, comprising: an intelligent integrated terminal, an inverter power control module for a photovoltaic power generation system, an on-load tap-changing controller for a high overload transformer tap-changing system, and a high overload on-load tap-changing distribution transformer; wherein, the high overload on-load tap-changing distribution transformer is internally equipped with an integrated monitoring device and an on-load tap-changing tap changer; the intelligent integrated terminal is connected to the inverter power control module, the on-load tap-changing controller, and the integrated monitoring device respectively; the on-load tap-changing controller is connected to the on-load tap-changing tap changer, and the on-load tap-changing tap changer is connected to the integrated monitoring device. The monitoring device includes: an on-load tap changer for collecting operating data of the high-overload on-load tap-changing distribution transformer and uploading it to the integrated monitoring device; an integrated monitoring device for collecting status data of the high-overload on-load tap-changing distribution transformer itself, and for fusing the collected status data and operating data of the on-load tap changer, uploading the processed data to the intelligent fusion terminal; and an intelligent fusion terminal for receiving the uploaded data, evaluating the health status of the high-overload on-load tap-changing distribution transformer and the power quality of the distribution area based on the data, and generating and issuing control commands to the inverter power control module or the on-load tap changer controller based on the evaluation results.

[0005] Furthermore, the integrated monitoring device collects its own status data, including non-electrical quantity data; the on-load tap changer's operating data includes both electrical and non-electrical quantity data; the non-electrical quantity data includes oil temperature, oil pressure, oil level, partial discharge signal, trace water content, winding temperature, and switch operation information; the electrical quantity data includes voltage and current data.

[0006] Furthermore, the integrated monitoring device processes non-electrical quantity data, including anomaly data identification, as follows: Based on a sliding window, the data sequence is monitored, and data points that deviate from the average threshold or have excessively large differences between adjacent data points are identified as anomaly data points, forming an anomaly data set; the continuity of data in the anomaly data set is judged, and continuously occurring anomaly data is determined as valid anomaly data, while isolated anomaly data points are determined as invalid noise data; the valid anomaly data is uploaded to the intelligent fusion terminal.

[0007] Furthermore, the intelligent fusion terminal assesses the health status of the on-load tap-changing distribution transformer under high overload conditions, specifically as follows: a health status assessment system containing multiple levels of indicators is constructed; the relative deterioration degree of each underlying assessment indicator is calculated; based on the relative deterioration degree, the weight of each assessment indicator is determined using a variable weight method; and combined with the weights, an evidence-based fusion method is used to calculate the comprehensive health status level of the on-load tap-changing distribution transformer under high overload conditions.

[0008] Furthermore, the health status levels include normal status, attentive status, abnormal status, and severe status.

[0009] Furthermore, the intelligent converged terminal assesses the power quality of the distribution area by calculating the reactive power adequacy of the low-voltage power grid.

[0010] Furthermore, the control commands generated by the intelligent fusion terminal make differentiated decisions based on the health status level of the on-load tap-changing distribution transformer under high overload conditions, as follows: When the health status is normal, the on-load tap-changing controller is prioritized for voltage regulation, supplemented by fine-tuning by the inverter power control module; when the health status is warning, the inverter power control module is prioritized for voltage regulation, and the number of actions of the on-load tap-changing controller is limited; when the health status is abnormal, only the inverter power control module is controlled for voltage regulation; when the health status is severe, reactive power regulation through the inverter power control module is stopped.

[0011] The control method of the intelligent control system for high overload on-load tap-changing distribution transformers based on intelligent fusion terminals, as described in this invention, includes the following steps:

[0012] (1) Collect multi-mode operation data and status data of high overload on-load tap-changing distribution transformers;

[0013] (2) Perform data fusion processing on the collected data;

[0014] (3) Based on the fused data, assess the health status of the on-load tap-changing distribution transformer under high overload and the power quality of the distribution area;

[0015] (4) Based on the evaluation results, generate and implement control strategies for power control of photovoltaic inverters and on-load voltage regulation of high overload transformers.

[0016] Beneficial Effects: Compared with existing technologies, this invention has the following significant advantages: This invention proposes an intelligent control system and method for on-load tap-changing distribution transformers under high overload conditions based on an intelligent fusion terminal. The fusion terminal performs unified processing and control, combining the health status of the high overload distribution transformer itself. It regulates the on-load tap changer and photovoltaic inverter under complex operating conditions and varying voltage fluctuations, ensuring accurate and efficient voltage regulation under different operating conditions. In particular, when the health status of the high overload transformer changes, the system can flexibly adjust the voltage regulation strategy, avoiding the fixed regulation method in traditional technologies, thus improving the stability of grid voltage regulation and the service life of equipment. Attached Figure Description

[0017] Figure 1 This is a flowchart of the present invention;

[0018] Figure 2 This is the abnormal data identification process of the present invention;

[0019] Figure 3 This invention provides a health status assessment index system for distribution transformers.

[0020] Figure 4 This invention provides a health status assessment process for distribution transformers. Detailed Implementation

[0021] The technical solution of the present invention will be further described below with reference to the accompanying drawings.

[0022] like Figure 1 As shown, this embodiment of the invention provides an intelligent control system for high overload on-load tap-changing distribution transformers based on an intelligent fusion terminal, comprising: an intelligent fusion terminal, an inverter power control module for a photovoltaic power generation system, an on-load tap-changing controller for a high overload transformer tap-changing system, and a high overload on-load tap-changing distribution transformer; wherein, the high overload on-load tap-changing distribution transformer is internally equipped with an integrated monitoring device and an on-load tap-changing switch; the intelligent fusion terminal is connected to the inverter power control module, the on-load tap-changing controller, and the integrated monitoring device respectively, the on-load tap-changing controller is connected to the on-load tap-changing switch, and the on-load tap-changing switch is connected to the integrated monitoring device.

[0023] The on-load tap changer uploads its collected operating data to the integrated monitoring device. The integrated monitoring device then merges its own collected data (including oil temperature, oil pressure, oil level, partial discharge signals, and trace moisture content) with the data collected by the on-load tap changer (including winding temperature, voltage, current, and switch operation information), and uploads the processed results to the intelligent fusion terminal. The uploaded data is categorized into non-electrical quantity data (oil temperature, oil pressure, oil level, partial discharge signals, trace moisture content, winding temperature, and switch operation information) and electrical quantity data (voltage and current) to achieve a comprehensive assessment of the health and operating status of the distribution transformer.

[0024] The integrated monitoring device employs a non-intrusive fusion sensing system to process and identify data related to distribution transformer oil temperature, oil pressure, oil level, partial discharge, moisture content, winding temperature, and switch operation status. Abnormal monitoring data is then added to the abnormal data set Q. The identification process is as follows:

[0025] Starting from the initial collection time of the non-electrical quantity data, a fixed sliding window h of length w is added. w (x t wCalculate the average and neighbor difference of data points within the sliding window. If a point deviates from the average threshold or the difference between adjacent data points is too large, it is considered an outlier and added to the outlier data set Q. Determine the data type of the outlier dataset Q. First, if outliers appear consecutively over a period of time, they are considered valid outliers and their operational status needs to be evaluated. Second, if isolated outliers appear among consecutive normal data points, they are considered noise points and invalid outliers caused by external interference, which can be ignored. The flowchart for outlier data identification is as follows. Figure 2 As shown, the abnormal data set Q is then uploaded to the fusion terminal, which assesses the health status of the distribution transformer.

[0026] Electrical quantity data includes both voltage and current data. Data characteristics can determine the operating condition of a high-overload distribution transformer, and this operating condition will serve as a reference benchmark for determining non-electrical quantity anomalies. The data processing and uploading process is as follows: The on-load tap changer collects the raw electrical quantity data: amplitudes of Va, Vb, and Vc; amplitudes of Ia, Ib, and Ic; current direction indicators (forward / reverse power flow); and sampling timestamps. The data is then uploaded to the integrated monitoring device for processing. After processing, the data is uploaded to the fusion terminal, which performs a power quality assessment of the distribution transformer in the area.

[0027] The intelligent fusion terminal is used to receive data uploaded by the integrated monitoring device in the high overload on-load tap-changing distribution transformer and data from the on-load tap-changing switch. Based on the above data, it judges the health status of the high overload distribution transformer and the power quality of the high overload distribution transformer in the transformer area, and formulates a voltage regulation strategy. The voltage regulation strategy is sent to the photovoltaic power generation system and the high overload distribution transformer voltage regulation system, which respectively control the inverter power control module and the on-load tap-changing controller.

[0028] The health status assessment process for distribution transformers is as follows:

[0029] S1. By analyzing the index parameters of distribution transformers, a three-tiered health status assessment index system for distribution transformers was determined, including the target layer, the primary index layer, and the secondary index layer. The health status assessment index system for distribution transformers is as follows: Figure 3 As shown. The relative degradation of the secondary indicators is calculated using the following formula. Quantitative indicators are categorized into larger-than-expected and smaller-than-expected indicators based on their properties. The indicators are then normalized to map the results to the [0,1] interval.

[0030] For indicators that are considered better the larger they are, the calculation formula is as follows:

[0031] (1-1)

[0032] For indicators that are better the smaller they are, the calculation formula is as follows:

[0033] (1-2)

[0034] in, X represents the normalized degradation degree of the indicator, where X is the measured value of the indicator. The maximum value of the indicator. This represents the minimum value of the indicator.

[0035] Monitoring indicators and data exhibit data flow characteristics; therefore, the application of online data in status assessment also requires consideration of data continuity. An exponential decay function is used to smooth the monitoring data, reducing over-response to extremely large data points. The calculation formula is as follows:

[0036] (1-3)

[0037] in, The degree of degradation after normalization of the indicator. 'a' represents the value of the indicator at a certain moment, and 'a' represents the attention value of the indicator, which is set according to the over-limit warning in the alarm information of the monitoring system.

[0038] S2. Classify the transformer health status levels, use the analytic hierarchy process (AHP) to clarify the constant weights of the primary and secondary indicators, and then combine them with the relative deterioration of each indicator to obtain the corresponding variable weights according to the following formula.

[0039] Constant weight vector:

[0040]

[0041] Weighting values ​​for each parameter:

[0042] (1-4)

[0043] Where α is the variable weighting coefficient, and α = 0.2 is taken; These are constant weights.

[0044] Then the variable weight vector:

[0045] (1-5)

[0046] S3. Using the set pair analysis method, the correlation between each evaluation index and the health status level of the distribution transformer is calculated according to Equations (1-6) to (1-11), and the comprehensive correlation between the quantitative index and the monitoring index is calculated sequentially using Equation (1-12).

[0047] (1-6)

[0048] in, , Indicates the threshold between each state level; when Normal state; when Abnormal state; when Severe condition;

[0049] (1-7)

[0050] in, This indicates the weight of each evaluation indicator. To assess the correlation between indicators and the health status level of distribution transformers.

[0051] S4. The comprehensive connectivity obtained in (1-7) As the initial basic probability assignment function of evidence theory:

[0052] (1-8)

[0053] A composite impact factor α is set, which combines the degree of index degradation. and timeliness This is an important factor used to correct the Basic Probability Assignment (BPA). It represents the degree of influence on the body of evidence through the product of these two factors.

[0054] (1-9)

[0055] The initial BPA function was corrected using a composite influence factor α. The corrected BPA is shown below. for:

[0056] (1-10)

[0057] The modified BPA is weighted and fused using formula (1-11). Assuming there are multiple evidence bodies, they are fused by weighted averaging to calculate the final fusion result. Formula (1-11) is typically in the form of a weighted sum:

[0058] (1-11)

[0059] in It is the final fused BPA. It is the weight of the i-th piece of evidence, representing the contribution of each piece of evidence to the final evaluation result.

[0060] The Dempster combination rule is used to further fuse the data to obtain the final health status assessment result. The Dempster rule normalizes and combines the modified results of multiple evidence bodies to obtain the final fused BPA.

[0061] (1-12)

[0062] S5. The fusion results are judged using three major decision-making criteria, thereby clarifying the health status level of the equipment and conducting a specific analysis. For example... Figure 4 As shown.

[0063] The power quality assessment of the distribution transformers in the substation involves processing the collected electrical quantity data and calculating the adequacy of the network's reactive power to prepare for subsequent voltage regulation strategies.

[0064] (1-13)

[0065] In the formula: For the reactive power margin of the low-voltage power grid; This represents the highest voltage across all photovoltaic nodes in the line. This refers to the reference value for voltage exceeding the upper limit; This is the sum of the reactive power sensitivity of all photovoltaic access nodes i to voltage control node j; Let be the maximum reactive power regulation capacity of the photovoltaic inverter at node j.

[0066] Intelligent control strategy: Integrate terminal assessment of the health status of high overload distribution transformers and power quality, and issue control commands to the photovoltaic power generation system-inverter power control module and the transformer voltage regulation system-on-load tap changer based on the four transformer health statuses.

[0067] (1) The high overload transformer is in a normal health state, and the OLTC-inverter coordinated control is as follows: Under normal conditions, the transformer operates stably without obvious faults, and voltage regulation can rely on traditional control equipment. At this time, the voltage regulation strategy first prioritizes the use of the OLTC (on-load tap changer) to significantly regulate the voltage, bringing it from the over-limit state to the inverter's controllable range. During this process, the OLTC adjusts the taps according to the voltage deviation, so that the voltage quickly recovers to a level close to the target voltage.

[0068] (2) High overload transformer health status is "Attention", inverter-OLTC coordinated control: In the "Attention" state, if the transformer exhibits minor abnormalities or potential faults, the voltage regulation strategy should prioritize using the inverter for voltage regulation, reducing the load and decreasing reliance on the OLTC to ensure that the equipment is not affected by excessive load. During this process, the fusion terminal will further limit the number of OLTC operations to avoid mechanical wear or increased equipment burden caused by frequent tap switching.

[0069] (3) When the health status of a high overload transformer is abnormal, only the inverter should be used for regulation: In the abnormal state, the transformer has serious problems, such as overload or excessive temperature rise. At this time, the reliance on OLTC should be reduced and the inverter should be completely used for regulation to avoid further increasing the mechanical burden and failure risk of using OLTC.

[0070] (4) When the high overload transformer is in a critical health state, stop the inverter reactive power regulation: In a critical state, the transformer has already suffered a serious fault, and the primary goal of the voltage regulation strategy is to protect the equipment from further damage.

Claims

1. A high-overload on-load tap-changing distribution transformer intelligent control system based on an intelligent fusion terminal, characterized in that, include: The system comprises an intelligent integrated terminal, an inverter power control module for a photovoltaic power generation system, an on-load tap changer for a high overload transformer voltage regulation system, and a high overload on-load tap-changing distribution transformer. The high overload on-load tap-changing distribution transformer is internally equipped with an integrated monitoring device and an on-load tap changer. The intelligent integrated terminal is connected to the inverter power control module, the on-load tap changer, and the integrated monitoring device. The on-load tap changer is connected to the on-load tap changer, which in turn is connected to the integrated monitoring device. The on-load tap changer collects operating data from the high overload on-load tap-changing distribution transformer and uploads it to the integrated monitoring device. The integrated monitoring device collects status data of the high overload on-load tap-changing distribution transformer itself and processes the collected status data and operating data from the on-load tap changer. The data is processed and uploaded to the intelligent fusion terminal. The intelligent fusion terminal receives the uploaded data, assesses the health status of the on-load tap-changing distribution transformer under high overload conditions and the power quality of the distribution area based on the data, and generates and issues control commands to the inverter power control module or on-load tap-changing controller based on the assessment results. Specifically, the intelligent fusion terminal assesses the health status of the on-load tap-changing distribution transformer under high overload conditions by: constructing a health status assessment system with multiple layers of indicators; calculating the relative degradation degree of each underlying assessment indicator; determining the weight of each assessment indicator using a variable weighting method based on the relative degradation degree; and calculating the comprehensive health status level of the on-load tap-changing distribution transformer using an evidence-based fusion method, combining the weights. The intelligent fusion terminal assesses the power quality of the distribution area by calculating the reactive power adequacy of the low-voltage power grid.

2. The intelligent control system for high overload on-load tap-changing distribution transformers based on an intelligent fusion terminal according to claim 1, characterized in that, The integrated monitoring device collects its own status data, including non-electrical data; the on-load tap changer's operating data includes both electrical and non-electrical data; the non-electrical data includes oil temperature, oil pressure, oil level, partial discharge signal, trace water content, winding temperature, and switch action information; Electrical quantity data includes voltage and current data.

3. The intelligent control system for high overload on-load tap-changing distribution transformers based on an intelligent fusion terminal according to claim 2, characterized in that, The integrated monitoring device processes non-electrical quantity data, including anomaly identification, as follows: Based on a sliding window, the data sequence is monitored, and data points that deviate from the average threshold or have excessively large differences between adjacent data points are identified as anomaly data points, forming an anomaly data set; the continuity of data in the anomaly data set is judged, and continuously occurring anomaly data is determined as valid anomaly data, while isolated anomaly data points are determined as invalid noise data; Upload valid abnormal data to the intelligent fusion terminal.

4. The intelligent control system for high overload on-load tap-changing distribution transformers based on an intelligent fusion terminal according to claim 1, characterized in that, Health status levels include normal, attentive, abnormal, and severe.

5. The intelligent control system for high overload on-load tap-changing distribution transformers based on an intelligent fusion terminal according to claim 1, characterized in that, The control commands generated by the intelligent converged terminal make differentiated decisions based on the health status level of the on-load tap-changing distribution transformer under high overload, as follows: When the health status is normal, the on-load tap-changing controller is prioritized for voltage regulation, supplemented by fine-tuning by the inverter power control module; when the health status is "attention," the inverter power control module is prioritized for voltage regulation, and the number of actions of the on-load tap-changing controller is limited; when the health status is "abnormal," only the inverter power control module is controlled for voltage regulation; when the health status is "severe," reactive power regulation through the inverter power control module is stopped.

6. A control method for a high-overload on-load tap-changing distribution transformer intelligent control system based on an intelligent fusion terminal according to claim 1, characterized in that, Includes the following steps: (1) Collect multi-mode operation data and status data of high overload on-load tap-changing distribution transformers; (2) Perform data fusion processing on the collected data; (3) Based on the fused data, assess the health status of the on-load tap-changing distribution transformer under high overload and the power quality of the distribution area; (4) Based on the evaluation results, generate and implement control strategies for photovoltaic inverter power control and / or transformer on-load tap changer.

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