Optimization method and system for prolonging life of transformer in cooperation with optical storage and charging

Abstract

This invention discloses a photovoltaic-storage-charging collaborative optimization method and system for extending transformer lifespan, relating to the field of power supply or distribution circuit systems. The method includes: collecting the operating status of the distribution network and calculating the hot spot temperature of the transformer windings to determine thermal overload; disconnecting non-critical loads during overload; forming candidate restoration access schemes based on the transformer's heat dissipation trend after disconnection and the current increment of the high-priority loads to be restored, and performing thermal safety margin verification; if the verification fails, calling the energy storage system for discharge support and re-verifying; after successful verification, closing the distribution switch step by step, and executing pause, delay, or rollback actions based on real-time thermal status and current feedback. This invention, through multi-dimensional pre-verification and energy storage discharge linkage, effectively suppresses the vicious cycle from overload to unloading to restoration to re-overload, reduces the equivalent power supply pressure on the transformer, and improves the power supply continuity and equipment safety during the thermal recovery phase of the photovoltaic-storage-charging network.

Description

Technical Field

[0001] This invention relates to the field of power supply or distribution circuit systems, and specifically to a method and system for co-optimization of photovoltaic, energy storage and charging to extend transformer lifespan. Background Technology

[0002] With the increasing application of photovoltaic power generation, energy storage systems and electric vehicle charging facilities in industrial and commercial parks, public buildings, integrated energy stations and distribution substations, the distribution transformers in the photovoltaic-storage-charging distribution network need to withstand the power changes caused by photovoltaic output fluctuations, energy storage charging and discharging switching and concentrated charging load access, which in turn affects the transformer load rate and winding heating status.

[0003] In existing power supply or distribution systems, transformer overheat protection is typically triggered by oil temperature, winding temperature, or load current exceeding a threshold, and reduces the transformer load by means of alarms, tripping, partial load shedding, or disconnecting power supply branches. For photovoltaic-storage-charging-distribution networks, existing control methods may also perform load shedding or restoration based on the energy storage's state of charge or load priority.

[0004] However, transformer thermal response exhibits a hysteresis. If high-priority loads are restored in a fixed sequence only after the temperature drops below the threshold, the current increment generated by the restored loads will still cause new copper loss heating, leading to a resurgence in the winding hot spot temperature and causing the distribution transformer to enter a cycle of overload-unloading-restoration-overload. Furthermore, existing energy storage systems are mostly used as backup power, peak shaving, or emergency power resources, and are typically not effectively linked to the switching conditions of the distribution switches during the transformer thermal recovery phase, making it difficult to reduce the equivalent current on the transformer side when the restoration of high-priority loads is limited.

[0005] Currently, there is a lack of a photovoltaic-storage-charging collaborative optimization scheme for extending transformer lifespan that can effectively solve the above problems.

[0006] The information disclosed in this background section is intended only to enhance the understanding of the overall background of the invention and should not be construed as an admission or in any way implying that the information constitutes prior art known to those skilled in the art. Summary of the Invention

[0007] The purpose of this invention is to provide a method and system for co-optimization of photovoltaic, energy storage, and charging to extend transformer lifespan. This method addresses the problem that existing photovoltaic, energy storage, and charging power distribution networks lack pre-closing verification of the distribution switch based on the transformer's heat dissipation trend, the increment of the load current to be restored, and the discharge support capability of the energy storage system during the power restoration phase after the transformer thermal overload protection is triggered. This can easily lead to secondary overheating, repeated tripping, and unstable restoration of critical loads.

[0008] On one hand, this invention provides a photovoltaic-storage-charging collaborative optimization method for extending transformer lifespan. This method is applied to a photovoltaic-storage-charging distribution network including a distribution transformer, photovoltaic power generation units, an energy storage system, charging loads, multiple feeder branches, and controlled distribution switches. The method includes: collecting the transformer thermal state, load current of each feeder branch, state of charge of the energy storage system, distribution switch status, and load node priority of the photovoltaic-storage-charging distribution network; determining the estimated value of the transformer winding hot spot temperature based on the transformer thermal state and the load current of each feeder branch, and determining whether the distribution transformer is in a thermal overload state based on the estimated value of the winding hot spot temperature; when the distribution transformer is in a thermal overload state, outputting a trip control signal to the corresponding controlled distribution switch according to the load node priority and the load current of each feeder branch to disconnect non-critical load branches; obtaining the transformer heat dissipation trend after the non-critical load branches are disconnected, and forming candidate recovery connections based on the load current increment of the high-priority load to be restored, the distribution switch address, and the transformer heat dissipation trend. The proposed recovery scheme involves: verifying the predicted highest winding hot spot temperature corresponding to the candidate recovery scheme with a thermal safety margin; if the verification fails and the energy storage system has discharge support capability, outputting a discharge power setpoint to the power conversion unit of the energy storage system, and re-verifying the thermal safety margin based on the equivalent load current after discharge support by the energy storage system; if the thermal safety margin verification passes, closing the corresponding controlled distribution switch step by step according to the corresponding candidate recovery scheme, and pausing, delaying, or reverting subsequent recovery actions based on real-time transformer thermal status and feeder branch load current feedback during the closing process.

[0009] Optionally, the acquisition of the transformer thermal state, load current of each feeder branch, state of charge of the energy storage system, state of distribution switch status, and load node priority of the photovoltaic-storage-charging-distribution network includes: obtaining the top oil temperature through a temperature probe installed at the oil temperature measurement location of the distribution transformer; obtaining the ambient temperature through an ambient temperature sensor; obtaining the load current of each feeder branch through a current transformer; obtaining the bus voltage through a voltage transformer; obtaining the opening and closing status of the controlled distribution switch through a switch quantity acquisition terminal; and reading the state of charge and allowable discharge status of the energy storage system through the battery management unit communication interface.

[0010] Optionally, determining the estimated value of the transformer winding hot spot temperature based on the transformer thermal state and the load current of each feeder branch includes: using the top oil temperature and ambient temperature measured on-site as the thermal state basis, using the load rate calculated from the load current of each feeder branch as the heat generation intensity input, and combining the transformer rated current, rated winding temperature rise and thermal model index calibrated during system initialization or maintenance phases to obtain the estimated value of the winding hot spot temperature.

[0011] Optionally, the load node priority is determined by at least one of the following: power supply guarantee level, load type, historical power consumption statistics record, and operation and maintenance configuration table; the non-critical load branches include feeder branches with priority lower than the preset priority boundary and not belonging to continuous production, emergency power supply, or safety guarantee loads.

[0012] Optionally, the step of outputting a trip control signal to the corresponding controlled distribution switch according to the load node priority and the load current of each feeder branch includes: first screening non-critical load branches, then determining the disconnection sequence in the non-critical load branches according to the current feeder branch load current from large to small, and outputting a trip control signal to at least one of the circuit breaker, contactor or solid-state relay.

[0013] Optionally, obtaining the transformer heat dissipation trend after the non-critical load branch is disconnected includes: continuously collecting the top oil temperature, the estimated winding hot spot temperature, and the feeder branch load current within the monitoring window after the non-critical load branch is disconnected; calculating the slope of the heat dissipation trend of the estimated winding hot spot temperature changing with time within the monitoring window; and using the heat dissipation trend slope to characterize the transformer heat dissipation trend.

[0014] Optionally, the candidate recovery access scheme includes the high-priority load branch to be restored, the proposed closing time, the address of the corresponding controlled distribution switch, the load current increment to be restored, and the candidate access interval; the candidate access interval is dynamically determined based on the transformer heat dissipation trend, the estimated value of the winding hot spot temperature, the thermal safety threshold, and the temperature fluctuation safety margin.

[0015] Optionally, the energy storage system having discharge support capability means that the energy storage system's state of charge is higher than the discharge lower limit, the power conversion unit is in an available state, the allowable discharge duration meets the support duration required by the candidate recovery access scheme, and the available output power of the power conversion unit can cover at least a portion of the load power to be supported by the high priority load to be restored.

[0016] Optionally, the step of pausing, delaying, or reversing subsequent restoration actions based on real-time transformer thermal status and feeder branch load current feedback includes: after any controlled distribution switch is closed, if the estimated value of the winding hot spot temperature reaches or exceeds the restoration closing judgment boundary formed by subtracting the temperature fluctuation safety margin from the thermal safety threshold, the temperature rise rate exceeds the temperature rise deviation threshold, the feeder branch load current suddenly increases, or the energy storage system discharge state is abnormal, then the subsequent closed control switch is paused, and the heat dissipation trend acquisition or non-critical load unloading steps are re-entered.

[0017] On the other hand, the present invention also provides a photovoltaic-storage-charging collaborative optimization system for extending transformer lifespan. The system comprises: a status acquisition module for acquiring the transformer thermal state, load current of each feeder branch, state of charge of the energy storage system, distribution switch status, and load node priority of the photovoltaic-storage-charging distribution network; a thermal overload identification module for determining the estimated winding hot spot temperature of the distribution transformer based on the transformer thermal state and the load current of each feeder branch, and identifying whether the distribution transformer is in a thermal overload state; a non-critical load disconnection module for controlling the corresponding controlled distribution switch to disconnect non-critical load branches based on the load node priority and the load current of each feeder branch when the distribution transformer is identified as being in a thermal overload state; and a candidate recovery access scheme formation module for determining the non-critical load branch status after the non-critical load branch is disconnected. The system analyzes the transformer heat dissipation trend, the load current increment of the high-priority load to be restored, and the address of the distribution switch to form a candidate restoration access scheme. The system then performs a thermal safety margin check on the candidate restoration access scheme. An energy storage system support verification module is used to determine whether the energy storage system has discharge support capability when the candidate restoration access scheme fails the thermal safety margin check. If it does, it outputs a discharge power setpoint to the power conversion unit of the energy storage system and re-verifies the thermal safety margin based on the equivalent load current after the energy storage system's discharge support. A restoration execution feedback module is used to close the corresponding controlled distribution switch step-by-step according to the candidate restoration access scheme when the candidate restoration access scheme passes the thermal safety margin check. Based on the real-time transformer thermal status and feeder branch load current feedback, it pauses, delays, or rolls back subsequent restoration access actions.

[0018] The beneficial effects of this invention are as follows: This invention uses the transformer winding hot spot temperature, the heat dissipation trend after the non-critical load is unloaded, the current increment of the high-priority load to be restored, and the energy storage discharge capacity as the pre-control basis for the closing of the distribution switch, so that the restoration access action no longer depends solely on static priority or a single temperature threshold; by calling the energy storage system to discharge support when restoration is limited, the equivalent power supply pressure on the transformer side is reduced; and by using the temperature rise feedback pause or rollback mechanism during the execution process, the power supply continuity and equipment thermal safety of the photovoltaic-storage-charging-distribution network during the thermal recovery phase are improved. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the overall process of the photovoltaic-storage-charging collaborative optimization method for extending transformer lifespan provided in Embodiment 1 of the present invention. Figure 2 This is a schematic diagram of the photovoltaic-storage-charging collaborative optimization system for extending transformer lifespan, provided in Embodiment 3 of the present invention. Figure 3This is a flowchart illustrating the status acquisition, thermal overload identification, and non-critical load disconnection process in Embodiment 2 of the present invention. Figure 4 This is a flowchart illustrating the process of obtaining heat dissipation trends and forming candidate recovery access schemes in Embodiment 2 of the present invention. Figure 5 This is a flowchart illustrating the thermal safety margin verification and discharge support verification process of the energy storage system in Embodiment 2 of the present invention. Figure 6 This is a flowchart illustrating the process of restoring access execution, real-time feedback, and abnormal rollback in Embodiment 2 of the present invention. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only for explaining the invention and are not intended to limit the invention; that is, the described embodiments are merely some embodiments of the invention, and not all embodiments. The components of the embodiments of the invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0021] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0022] It should be noted that relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0023] As mentioned earlier, transformer thermal response exhibits a hysteresis. If high-priority loads are restored in a fixed sequence only after the temperature drops below the threshold, the current increment generated by the restored loads will still cause new copper loss heating, leading to a resurgence in the winding hot spot temperature and causing the distribution transformer to enter a cycle of overload-unloading-restoration-overload. Furthermore, existing energy storage systems are mostly used as backup power, peak shaving, or emergency power resources, and are typically not effectively linked to the switching conditions of the distribution switches during the transformer thermal recovery phase, making it difficult to reduce the equivalent current on the transformer side when the restoration of high-priority loads is limited.

[0024] To address this, the present invention provides a photovoltaic-storage-charging collaborative optimization method and system for extending transformer lifespan, solving the aforementioned problems in the following manner. (The following section combines...) Figures 1 to 6 Further explanation.

[0025] Example 1: Please refer to the accompanying drawings in the instruction manual, such as... Figure 1 As shown, this embodiment provides a photovoltaic-storage-charging collaborative optimization method for extending transformer lifespan. This method is applied to a photovoltaic-storage-charging distribution network including a distribution transformer, photovoltaic power generation unit, energy storage system, charging load, multiple feeder branches, and controlled distribution switches. The actuator can be a controller. The method includes the following steps: S100. Collect the transformer thermal status, load current of each feeder branch, energy storage system charge status, distribution switch status and load node priority of the photovoltaic energy storage charging and distribution network. S200. Determine the estimated value of the transformer winding hot spot temperature based on the thermal state of the transformer and the load current of each feeder branch, and determine whether the distribution transformer is in a thermal overload state based on the estimated value of the winding hot spot temperature. S300: When the distribution transformer is in a thermal overload state, according to the load node priority and the load current of each feeder branch, output a trip control signal to the corresponding controlled distribution switch to disconnect the non-critical load branch. S400: Obtain the heat dissipation trend of the transformer after the non-critical load branch is disconnected, and form a candidate restoration access scheme based on the load current increment of the high priority load to be restored, the address of the distribution switch and the heat dissipation trend of the transformer. S500. Perform thermal safety margin verification on the predicted highest winding hot spot temperature corresponding to the candidate recovery access scheme. If the verification fails and the energy storage system has discharge support capability, output the discharge power setting value to the power conversion unit of the energy storage system, and re-verify the thermal safety margin based on the equivalent load current after the energy storage system discharges. S600: After passing the thermal safety margin check, the corresponding controlled power distribution switch is closed step by step according to the corresponding candidate restoration access scheme. During the closing process, the subsequent restoration access action is suspended, delayed or reverted based on the real-time transformer thermal status and feeder branch load current feedback.

[0026] Based on the above steps, this invention transforms the load recovery process after thermal overload into a step-by-step recovery process constrained by heat dissipation capacity, the incremental recovery load, and the discharge support capacity of the energy storage system. This prevents the distribution transformer from rapidly overheating again due to the concentrated recovery of high-priority loads after the non-critical load is unloaded. Simultaneously, when recovery is limited, the energy storage system is invoked to undertake part of the recovery load demand, reducing the equivalent current pressure on the distribution transformer side during the recovery phase. This allows critical loads to be gradually connected without exceeding the thermal safety boundary. Furthermore, by pausing, delaying, or reverting subsequent actions through real-time feedback during the recovery process, the cycle of overload, unloading, recovery, and re-overload is suppressed, improving the power supply continuity, load recovery stability, and thermal safety margin of the distribution transformer in the thermal recovery phase of the photovoltaic-storage-charging-distribution network.

[0027] Example 2: Based on the above embodiments, in order to provide a clearer and more complete explanation of the technical solutions therein, the present invention also provides a second embodiment, in which the actuator can also be a controller.

[0028] like Figure 3 As shown, in this second embodiment, step S100 may further include: The top oil temperature is obtained by a temperature probe installed at the oil temperature measurement location of the distribution transformer, the ambient temperature is obtained by an ambient temperature sensor, the load current of each feeder branch is obtained by a current transformer, the bus voltage is obtained by a voltage transformer, the opening and closing status of the controlled distribution switch is obtained by a switch quantity acquisition terminal, and the state of charge and allowable discharge status of the energy storage system are read by the communication interface of the battery management unit.

[0029] For example, for instance: In one optional implementation, the controller collects various types of operational data at a preset sampling period, which is determined by the refresh capability of the field monitoring system, the thermal time constant of the distribution transformer, and the operation and maintenance procedures.

[0030] The top oil temperature is obtained by a temperature probe installed in the transformer box, oil temperature measurement hole, or integrated online monitoring device; the ambient temperature is obtained by an ambient temperature sensor installed near the transformer's operating environment; the load current of each feeder branch is obtained by the current transformer on the corresponding branch; the bus voltage is obtained by a voltage transformer; the status of the controlled distribution switch is obtained by auxiliary contacts or switch quantity acquisition terminals; and the state of charge, permissible discharge, and fault status of the energy storage system are obtained by the BMS communication interface.

[0031] The bus voltage, the load current of each feeder branch, and the total load current on the distribution transformer side are used to reflect the impact of photovoltaic output fluctuations, charging load changes, and energy storage charging and discharging switching on the distribution transformer load rate. When a photovoltaic inverter communication interface is configured on site, the controller can also read the operating status or output status of the photovoltaic power generation unit and use it as the operating boundary for judging the change of power flow direction on the distribution transformer side.

[0032] The controller adds sampling timestamps to the above data and aligns them according to the same sampling period to form an operating status table that includes the transformer's thermal status, electrical status, energy storage status, and load node status. For data that significantly exceeds the sensor's range, has missing timestamps, communication interruptions, or abrupt changes in sampling exceeding the maintenance threshold, the controller marks it as abnormal sampling and does not use it as a basis for resuming operation. For cases where critical data affecting thermal safety judgment is missing, the controller only allows the execution of actions such as maintaining power supply, reducing load, or issuing an alarm.

[0033] The load node priority table is written to the controller during system commissioning or maintenance, and is derived from at least one of the following: power supply guarantee level, load type, historical electricity consumption statistics, and operation and maintenance configuration table. This table must record at least the load node number, feeder address, rated power, whether it is an emergency backup target, whether delayed access is allowed, and whether dynamic current limiting is allowed.

[0034] In this second embodiment, step S200 may further include: Using the top oil temperature and ambient temperature measured on-site as the thermal state basis, the load rate calculated from the load current of each feeder branch as the heat generation intensity input, and combined with the transformer rated current, rated winding temperature rise and thermal model index calibrated during system initialization or maintenance, the estimated value of the winding hot spot temperature is obtained.

[0035] For example, for instance: In one optional implementation, the controller first converts the load current of each feeder branch into the total load current on the distribution transformer side, and then combines the top oil temperature and rated thermal parameters to obtain an estimated value for the winding hot spot temperature. This estimated value replaces the abstract heat level and serves as a unified thermal state parameter for thermal overload judgment and recovery verification. Ambient temperature is used to verify whether the top oil temperature change is within a reasonable range, and is used to correct subsequent heat dissipation monitoring window length, the conservatism of recovery verification, and the safety margin for temperature fluctuations. When the ambient temperature sensor malfunctions, the controller does not directly correct the estimated winding hot spot temperature based on the abnormal ambient temperature, but instead uses the top oil temperature and the equivalent current amplitude on the distribution transformer side for a conservative judgment.

[0036] In one possible implementation, the controller determines the winding hot spot temperature according to the following relationship:

[0037]

[0038]

[0039] in, For a moment Estimated winding hot spot temperature; The top oil temperature is measured on-site and collected by a temperature probe, fiber optic temperature measurement, or integrated online monitoring device. The oil temperature rise of the winding under rated load is determined based on manufacturer's tests, factory data, system initialization calibration, or on-site maintenance calibration results. Current load factor; The total load current is calculated by converting the current of each feeder branch; For the first The field-measured current of each feeder branch; used for winding heating calculations. The equivalent current value of the feeder branch is calculated based on the metering boundary of the same distribution transformer side. The total load current on the distribution transformer side is obtained by summing the equivalent current values ​​of each feeder branch; the directional information generated by the photovoltaic power output feedback or the discharge of the energy storage system is used to determine the power flow direction and equivalent conversion relationship, so as not to make Take the negative value.

[0040] The rated current of the distribution transformer is determined based on the transformer nameplate, equipment file, or manufacturer parameters. The thermal model index is determined by the transformer model, cooling method, and on-site calibration. The number of feeder branches is determined by the topology of the photovoltaic-storage-charging-distribution network.

[0041] When there are differences in current direction due to photovoltaic power feedback, energy storage system discharge, or charging load changes in feeder branches, the controller calculates the current of each feeder branch according to the equivalent current direction on the distribution transformer side and the relationship with the metering points. .

[0042] Thermal safety threshold The determination is based on the transformer model, insulation class, manufacturer's recommended operating limits, operating procedures, on-site trial operation data, or calibration results during the maintenance phase. If ≤ The controller returns to S100 to continue monitoring; if > The controller outputs a thermal overload trigger signal and initiates non-critical load directional unloading.

[0043] Among them, the thermal safety threshold, temperature fluctuation safety margin, and temperature rise deviation threshold are all stored as operating parameters in the controller. The thermal safety threshold is used to characterize the upper limit of the allowable winding hot spot temperature; the temperature fluctuation safety margin is used to deduct from the thermal safety threshold to form the boundary for resuming closing; the temperature rise deviation threshold is used to determine whether the actual temperature rise rate deviates from the predicted range after closing. The above parameters can be determined during the system initialization or maintenance phase based on at least one of the following: transformer manufacturer's data, operating procedures, field trial operation data, historical prediction errors, and sensor errors.

[0044] In this second embodiment, step S300 may further include: The priority of the load node is determined by at least one of the following: power supply guarantee level, load type, historical electricity consumption statistics record, and operation and maintenance configuration table. The non-critical load branches include feeder branches with a priority lower than the preset priority boundary and that do not belong to continuous production, emergency power supply or safety assurance loads.

[0045] For example, for instance: In one alternative implementation, priority boundaries are determined by an operations and maintenance configuration table or power supply assurance level. Continuous production lines, fire protection power supply, communication support equipment, emergency lighting branches, and backup branches explicitly defined in the user's power supply agreement are configured as high-priority loads; general office air conditioners, deferred power equipment, non-emergency charging piles, and other branches that are permissible to be interrupted are configured as non-critical loads.

[0046] When the same load node meets multiple classification conditions at the same time, the controller adopts the classification result with the higher protection level; when the priority table is missing or the classification of a node is unclear, the controller does not regard the node as a priority unloading object, but instead lists it as a node to be manually confirmed, so as to avoid misjudging critical protection loads as non-critical loads.

[0047] In this second embodiment, step S300 further includes: First, screen the non-critical load branches, then determine the disconnection sequence in the non-critical load branches according to the current feeder branch load current from large to small, and output a trip control signal to at least one of the circuit breaker, contactor or solid-state relay.

[0048] For example, for instance: In one alternative implementation, the controller sorts non-critical load branches in descending order of current feeder branch load current and determines the tripping target based on the actuability status of the controlled distribution switches. For branches with the same current contribution, the controller prioritizes branches with lower priority, allowable delayed recovery, and normal switch feedback.

[0049] The trip control signal is sent to the circuit breaker, contactor, or solid-state relay via I / O module, RS485, CAN, Ethernet, or other industrial communication buses. After the switch action is completed, the controller reads the feedback from the auxiliary contacts or the switch quantity acquisition terminal to confirm whether the branch has been disconnected. If a branch switch fails to operate, the controller marks the branch as an execution anomaly and selects the next disconnectable non-critical branch to continue unloading; if the winding hot spot temperature continues to rise after unloading, the non-critical load unloading range is expanded or the upper-level protection is triggered.

[0050] like Figure 4 As shown, in this second embodiment, step S400 may further include: Within the monitoring window after the non-critical load branch is disconnected, the top oil temperature, the estimated winding hot spot temperature, and the feeder branch load current are continuously collected. The heat dissipation trend slope of the estimated winding hot spot temperature over time within the monitoring window is calculated, and the heat dissipation trend slope of the transformer is used to characterize the heat dissipation trend of the transformer.

[0051] For example, for instance: In one optional implementation, the length of the heat dissipation monitoring window is determined by the thermal time constant of the distribution transformer, operating procedures, field trial operation data, or calibration results during maintenance, and can be dynamically extended based on ambient temperature and the status of the cooling device. Ambient temperature is used to reflect the external heat dissipation conditions of the distribution transformer. When the ambient temperature rises or the cooling device malfunctions, causing the heat dissipation conditions to deteriorate, the controller extends the heat dissipation monitoring window or increases the conservatism of the restoration connection verification.

[0052] The controller continuously reads the top oil temperature, feeder branch load current, and operating status of cooling fan or oil pump within the heat dissipation monitoring window, and calculates the changing trend of the estimated winding hot spot temperature.

[0053] Specifically, the controller subtracts the ending value from the estimated winding hot spot temperature within the heat dissipation monitoring window, and then divides the result by the monitoring window duration to obtain the cooling slope. .when When the value is greater than 0, it indicates that the estimated temperature of the winding hot spot is decreasing; when... When the value is ≤0, it indicates that the estimated temperature of the winding hot spot has not decreased or is still increasing.

[0054] When the slope of the heat dissipation trend indicates a decrease in the estimated temperature of the winding hot spot, it means that the distribution transformer is in a heat dissipation recovery state, and the controller allows the formation of a candidate recovery access scheme. ≤0 or will If the candidate recovery access scheme still cannot meet the recovery closing judgment boundary after the subsequent thermal safety margin check, the controller determines that the current heat dissipation trend is insufficient to support the load recovery access, prohibits immediate recovery access and returns to S300 to continue unloading non-critical loads, or outputs a cooling abnormality alarm.

[0055] In this second embodiment, step S400 further includes: The candidate recovery access scheme includes the high-priority load branch to be restored, the proposed closing time, the corresponding controlled power distribution switch address, the load current increment to be restored, and the candidate access interval; The candidate access interval is dynamically determined based on the transformer's heat dissipation trend, the current winding hot spot temperature estimate, the thermal safety threshold, and the temperature fluctuation safety margin.

[0056] For example, for instance: In one optional implementation, the high-priority loads to be restored are determined by cross-referencing the list of disconnected loads with the load node priority table. The list of disconnected loads includes high-priority load branches that were disconnected prior to the current thermal overload handling due to upstream protection, manual dispatching, historical overheat protection, or operation of the upstream distribution switch. It also includes high-priority load branches that were temporarily restricted from access during the thermal overload handling process due to safety policies. For high-priority loads disconnected due to upstream distribution switch operation, manual dispatching, or external protection, the controller only includes them in the candidate restoration access scheme after it has closing control authority, receives a restoration request, or receives a restoration permission instruction from the maintenance terminal.

[0057] The controller does not consider high-priority loads that are still under normal power supply as candidate restoration access targets. The controller reads the rated power, operating current before disconnection, most recent effective operating current, or real-time restoration request of each branch to be restored to determine the incremental load current for that branch. .

[0058] The candidate access interval is dynamically determined based on the current winding hotspot temperature, heat dissipation trend slope, thermal safety threshold, and temperature fluctuation safety margin. Specifically, the controller uses the estimated current winding hotspot temperature, heat dissipation trend slope, and the increment of the load current to be restored as inputs to predict the highest winding hotspot temperature under different candidate access intervals. When the predicted highest winding hotspot temperature corresponding to a certain candidate access interval does not exceed the value after deducting the temperature fluctuation safety margin from the thermal safety threshold, the controller determines the time corresponding to that candidate access interval as the proposed closing time. For each candidate restoration access scheme, the controller records the branch to be restored, the proposed closing time, the address of the corresponding controlled distribution switch, the increment of the load current to be restored, the candidate access interval, and whether energy storage discharge support is required.

[0059] If the increment of the load current to be restored for all candidate schemes If the calculated predicted highest winding hot spot temperature exceeds the value after deducting the temperature fluctuation safety margin from the thermal safety threshold, the controller will not generate an immediate recovery plan, but will instead generate a delayed recovery plan or enter the energy storage system for discharge support verification.

[0060] When performing thermal safety margin verification, the controller uses the estimated current winding hot spot temperature and heat dissipation trend after unloading as a basis, and the increment of the load current to be restored as an additional heat input to estimate the predicted highest winding hot spot temperature within the future verification time window, and determines whether to allow the distribution switch to be closed according to the following relationship:

[0061] in, The highest winding hot spot temperature predicted under the candidate recovery access scheme; The thermal safety threshold is determined by the transformer model, insulation class, manufacturer's recommended operating limits, operation and maintenance procedures, or on-site calibration. The temperature fluctuation safety margin is derived from at least one of the following: historical prediction errors, sensor errors, calibration results during maintenance, and conservative maintenance margin.

[0062] when ≤ When the controller allows the switch to close, the controller is authorized to proceed to the power distribution switch closing step. > If the controller determines that the candidate recovery access scheme has failed the thermal safety margin check, it will not perform an immediate closing action and will instead enter the energy storage system discharge support check or delayed recovery process.

[0063] The predicted maximum winding hot spot temperature is determined by the controller based on the current winding hot spot temperature estimate, heat dissipation trend, the increment of the load current to be restored, the rated current of the distribution transformer, the rated winding temperature rise, and the thermal model index. Specifically, the current winding hot spot temperature estimate serves as the prediction starting point; the predicted temperature drop within the candidate access interval is determined by the heat dissipation trend slope and the candidate access interval; and the additional winding temperature rise caused by the load to be restored is determined by the difference in winding temperature rise corresponding to the load rate before and after restoration.

[0064] The pre-restoration load factor is determined by the equivalent current amplitude on the distribution transformer side after the non-critical load branch is disconnected and the rated current of the distribution transformer; the post-restoration load factor is determined by superimposing the pre-restoration load factor with the equivalent current increment corresponding to the current increment of the load to be restored. The controller first determines the winding temperature rise difference between the pre-restoration load factor and the post-restoration load factor, and then uses this winding temperature rise difference as the additional winding temperature rise caused by the connection of the load to be restored.

[0065] The controller subtracts the predicted cooling amount within the candidate access interval from the current estimated winding hot spot temperature and adds the additional winding temperature rise caused by the access of the load to be restored, to obtain the predicted winding hot spot temperature at the corresponding candidate access time. If the same candidate restoration access scheme includes multiple candidate access times, the controller determines the maximum predicted winding hot spot temperature among the predicted winding hot spot temperatures corresponding to each candidate access time as the highest predicted winding hot spot temperature. If the same candidate restoration access scheme includes multiple branches to be restored, the controller updates the load rate after restoration one by one according to the order of the proposed closing time, and determines the maximum predicted winding hot spot temperature among the predicted winding hot spot temperatures obtained after each restoration access as the highest predicted winding hot spot temperature under the candidate restoration access scheme.

[0066] If the predicted highest winding hot spot temperature does not exceed the value after deducting the temperature fluctuation safety margin from the thermal safety threshold, the controller determines that the corresponding candidate recovery access scheme passes the thermal safety margin check; if the predicted highest winding hot spot temperature exceeds the value after deducting the temperature fluctuation safety margin from the thermal safety threshold, the controller determines that the corresponding candidate recovery access scheme fails the thermal safety margin check and enters the energy storage system discharge support check or delayed recovery processing.

[0067] like Figure 5 As shown, in this second embodiment, step S500 may further include: The energy storage system having discharge support capability means that the energy storage system's state of charge is higher than the discharge lower limit, the power conversion unit is in an available state, the allowable discharge duration meets the support duration required by the candidate recovery access scheme, and the available output power of the power conversion unit can cover at least a portion of the load power to be supported by the high priority load to be restored.

[0068] For example, for instance: In one alternative implementation, the controller reads SOC, allowable discharge status, fault status, and available capacity information from the BMS, and reads the available maximum output power and fault status from the PCS. When the SOC is not higher than the discharge lower limit, the PCS is unavailable, the BMS communication is abnormal, or the allowable discharge duration is insufficient, the controller does not use the energy storage system discharge support as a condition for passing the thermal safety check, but instead outputs a delayed recovery command and returns the heat dissipation trend acquisition.

[0069] When the discharge support conditions of the energy storage system are met, the controller generates a PCS discharge power setpoint, so that part of the power of the restored load is borne by the energy storage system, thereby reducing the equivalent load current on the distribution transformer side. The PCS discharge power setpoint is determined jointly based on the maximum available output power of the PCS, the load power to be supported corresponding to the candidate restoration access scheme, and the sustainable discharge power constrained by the SOC, and does not exceed any of the above constraint boundaries.

[0070] The maximum available output power of the PCS is determined by the PCS rated parameters and real-time operating status; the load power to be supported corresponding to the candidate recovery access scheme is determined by the rated power of the load to be restored, the operating power before disconnection, or the real-time recovery request; the sustainable discharge power constrained by SOC is determined by the battery state of charge, battery capacity, discharge efficiency, and the support duration required by the candidate scheme; the discharge lower limit is determined by the operation and maintenance strategy or battery protection strategy; the available battery capacity is determined by the BMS, equipment files, or operation and maintenance configuration; the PCS discharge efficiency is determined by the PCS manufacturer parameters, on-site testing, or maintenance calibration; and the support duration required by the candidate scheme is determined by the expected support time of the candidate recovery access scheme.

[0071] After determining the PCS discharge power setpoint, the controller first confirms that the PCS connection point of the energy storage system is located on the low-voltage side bus of the distribution transformer, or on the bus side sharing the same distribution transformer-side metering boundary as the branch of the load to be restored. It also confirms that the PCS discharge power can offset the increased active power demand on the distribution transformer side caused by the load to be restored within this metering boundary. Under the same metering cycle and the same bus voltage reference, the controller reduces the increment of the load current to be restored according to the ratio of the actual power borne by the PCS to the power of the load to be supported, and uses the reduced current increment as the equivalent restoration current increment after the energy storage system discharges. If the actual output power of the PCS is lower than the discharge power setpoint, the reduction is performed according to the proportion corresponding to the actual output power of the PCS. If the equivalent reduction relationship between the PCS connection point, the branch of the load to be restored, and the metering boundary on the distribution transformer side cannot be confirmed, or if the total incoming current on the transformer side does not reflect the reduction effect after PCS discharge, the controller does not perform current reduction and performs a conservative thermal safety margin check based on the increment of the load current to be restored.

[0072] Specifically, if the actual power carried by the PCS is less than the power of the load to be supported, the controller will use the portion of the incremental load current not carried by the PCS as the equivalent recovery current increment after the energy storage system discharges and supports the load. If the actual power carried by the PCS reaches the power of the load to be supported, the equivalent new active current generated by the load to be supported on the distribution transformer side during the corresponding support period will be treated as residual current not exceeding the allowable measurement deviation. If there is reactive current, line loss, or metering deviation, the controller will make conservative corrections based on the actual measured equivalent current on the transformer side. The controller will re-enter the equivalent recovery current increment after the energy storage system discharges and supports the load into the thermal safety margin check, and only after meeting the conditions will it be allowed to enter S600.

[0073] like Figure 6 As shown, in this second embodiment, step S600 may further include: If, after any controlled power distribution switch is closed, the estimated value of the winding hot spot temperature reaches or exceeds the recovery closing judgment boundary formed by subtracting the temperature fluctuation safety margin from the thermal safety threshold, the temperature rise rate exceeds the temperature rise deviation threshold, the feeder branch load current suddenly increases, or the energy storage system discharge state is abnormal, then the subsequent closed controllable power distribution switch is suspended, and the heat dissipation trend acquisition or non-critical load unloading steps are re-entered.

[0074] For example, for instance: In one optional implementation, the controller sequentially sends closing control signals to the corresponding controlled power distribution switches according to the verified candidate recovery access schemes; when the scheme includes discharge support for the energy storage system, it simultaneously sends a discharge power setting value to the PCS.

[0075] After each closing, the controller reads the switch status feedback, feeder branch load current, estimated winding hot spot temperature, bus voltage, and actual PCS output power to determine whether the actual operating status is still within the predicted range. A sudden increase in feeder branch load current refers to the measured feeder branch load current after the controlled distribution switch is closed exceeding the sum of the increment of the load current to be restored recorded in the candidate restoration access scheme and the allowable measurement deviation, or exceeding the current change limit of the corresponding branch in the operation and maintenance configuration table. An abnormal discharge status of the energy storage system refers to the actual output power of the PCS being lower than the allowable deviation range corresponding to the discharge power setting value, the PCS or BMS reporting a fault status, the allowable discharge status failing, or the SOC dropping to the lower discharge limit.

[0076] When the estimated winding hot spot temperature reaches or exceeds the recovery closing judgment boundary, the controller determines that there is a tendency to exceed the limit; the recovery closing judgment boundary is formed by subtracting the temperature fluctuation safety margin from the thermal safety threshold. When fiber optic temperature measurement or other direct winding temperature measurement devices are installed on site, the controller can also use the measured winding hot spot temperature as the above judgment basis.

[0077] Without a direct winding temperature measurement device, the controller uses the estimated winding hot spot temperature for thermal overload judgment, recovery verification, and feedback backoff judgment. With a direct winding temperature measurement device, the controller can use the measured winding hot spot temperature to replace or correct the estimated value, but the same thermal state parameter is used as the judgment basis within the same judgment cycle. The judgment boundary for the temperature rise rate exceeding the temperature rise deviation threshold is determined by historical prediction error statistics, sensor errors, and calibration results during maintenance.

[0078] If an over-limit trend occurs, the controller immediately suspends the closing of subsequent controlled power distribution switches and, depending on the source of the anomaly, selects to delay recovery, return to S400 to re-extract the heat dissipation trend, return to S300 to re-unload some non-critical loads, or disconnect the newly restored flexible charging load branch.

[0079] When all high-priority loads to be restored are restored according to the plan, and the estimated value of the winding hot spot temperature does not reach the restoration closing judgment boundary within the continuous stable monitoring window, the feeder branch load current does not suddenly increase, and the PCS output status is consistent with the set value, the controller outputs the stable power supply status under thermal safety constraints and returns to S100 to continue periodic monitoring.

[0080] Example 3: Based on the same general inventive concept, this invention also provides a photovoltaic-storage-charging collaborative optimization system for extending transformer lifespan, such as... Figure 2 As shown, the optical-storage-charging collaborative optimization system includes: The status acquisition module is used to collect the transformer thermal status, load current of each feeder branch, energy storage system charge status, distribution switch status and load node priority of the photovoltaic-storage-charging-distribution network. The thermal overload identification module is used to determine the estimated value of the winding hot spot temperature of the distribution transformer based on the thermal state of the transformer and the load current of each feeder branch, and to identify whether the distribution transformer is in a thermal overload state. The non-critical load disconnection module is used to control the corresponding controlled distribution switch to disconnect the non-critical load branch when the distribution transformer is detected to be in a thermal overload state, based on the load node priority and the load current of each feeder branch. The candidate recovery access scheme forming module is used to form candidate recovery access schemes based on the transformer heat dissipation trend after the non-critical load branch is disconnected, the load current increment of the high priority load to be restored, and the address of the distribution switch, and to perform thermal safety margin verification on the candidate recovery access schemes. The energy storage system support verification module is used to determine whether the energy storage system has discharge support capability when the candidate recovery access scheme fails the thermal safety margin verification. If it has discharge support capability, it outputs a discharge power setting value to the power conversion unit of the energy storage system and re-verifies the thermal safety margin based on the equivalent load current after the energy storage system discharges. The recovery execution feedback module is used to close the corresponding controlled power distribution switch step by step according to the candidate recovery access scheme when the candidate recovery access scheme passes the thermal safety margin check, and to suspend, delay or roll back the subsequent recovery access actions based on the real-time transformer thermal status and feeder branch load current feedback.

[0081] In the specific hardware layout, the status acquisition module includes a temperature probe, an ambient temperature sensor, a current transformer, a voltage transformer, and a switch status acquisition terminal. The temperature probe acquires the top oil temperature of the distribution transformer, the ambient temperature sensor acquires the operating ambient temperature, the current transformer acquires the load current of each feeder branch, the voltage transformer acquires the bus voltage, and the switch status acquisition terminal acquires the opening and closing feedback of circuit breakers, contactors, or solid-state relays.

[0082] The controller includes a processor, a memory, and a communication interface. The memory stores a load node priority table, transformer rated parameters, thermal model parameters, thermal safety threshold, temperature fluctuation safety margin, SOC lower limit, PCS power constraints, temperature rise deviation threshold, and a distribution switch address table. The processor executes the control steps described in S100 to S600. The communication interface is connected to the BMS, PCS, distribution switch actuator, charging pile controller, and maintenance terminal, respectively.

[0083] Controlled distribution switches are installed on each feeder branch to disconnect non-critical load branches under the action of the controller's trip control signal, or to restore high-priority load branches under the action of the controller's closing control signal. The energy storage system communication interface is used to receive SOC, allowable discharge status, fault status, and available capacity information output by the BMS; the power conversion unit control interface is used to output the active power discharge setpoint to the PCS and read the PCS's actual output power, maximum available output power, and fault status.

[0084] The collaborative relationship among the aforementioned hardware components is as follows: the status acquisition module provides the boundaries of thermal, electrical, and energy storage status; the thermal overload identification module converts these boundaries into a judgment result indicating whether unloading is required; the non-critical load disconnection module implements the judgment result into the tripping action of the controlled distribution switch; the candidate recovery access scheme formation module and the energy storage system support verification module convert the heat dissipation trend, the increment of the load current to be restored, and the energy storage discharge capacity into control conditions for whether closing is permitted; and the recovery execution feedback module forms a closed loop with closing, discharging, and feedback backoff. Specifically, the tripping or closing action of the controlled distribution switch, the discharge power output of the energy storage system, and the controller's feedback acquisition of the winding hot spot temperature estimate and the feeder branch load current are executed in conjunction within the same recovery control cycle; when any execution feedback is inconsistent with the controller's prediction result, the controller suspends subsequent closing actions and re-enters the heat dissipation trend acquisition or non-critical load unloading processing.

[0085] In an alternative implementation, the top oil temperature can be obtained by fiber optic temperature measurement, thermistor, infrared temperature measurement, or a comprehensive online monitoring device for the transformer; the winding hot spot temperature can be determined using thermal model parameters provided by the manufacturer, field calibration curves, equivalent thermal circuit models, or equivalent calculation rules permitted by the operation and maintenance procedures; the controlled distribution switch can be a circuit breaker, contactor, solid-state relay, or switching equipment with remote opening and closing capabilities. The above alternative methods only change the specific form of the acquisition or execution hardware, without altering the technical concept of using winding hot spot temperature and thermal safety margin as the conditions for restoring connection closure.

[0086] In another alternative implementation, when the charging pile supports dynamic current limiting, the controller can simultaneously issue a charging current limit when restoring the flexible charging load; when the charging pile does not support dynamic current limiting, the controller only achieves delayed access through the controlled distribution switch. When the photovoltaic inverter has a reactive power support or active power reduction interface, the controller can issue a reactive power support or active power reduction command when the bus voltage fluctuation or reverse power flow causes an increase in additional current pressure; when the on-site photovoltaic inverter does not support this interface, the present invention can still achieve thermal safety recovery control through distribution switch control and energy storage discharge support. In the present invention, the photovoltaic power generation unit participates in the control judgment at least as an operating boundary affecting the power flow direction and load rate changes on the distribution transformer side; the controller reflects the impact of photovoltaic output fluctuations on the transformer thermal state through changes in bus voltage, feeder branch load current, and total load current on the distribution transformer side, without requiring direct adjustment of the photovoltaic power generation unit output as a condition for the implementation of the present invention.

[0087] It should be understood that, in the embodiments of the present invention, "B corresponding to A" means that B is associated with A, and B can be determined based on A. However, it should also be understood that determining B based on A does not mean that B is determined solely based on A; B can also be determined based on A and / or other information.

[0088] Those skilled in the art will recognize that the units and algorithm steps of the various examples described in conjunction 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 and steps 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 this invention.

[0089] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the specific working processes of the systems, devices, and units described above can be referred to the corresponding processes in the foregoing method embodiments, and will not be repeated here.

[0090] In the embodiments provided in this application, it should be understood that the disclosed systems, apparatuses, and methods can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative; for instance, the division of units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the couplings or direct couplings or communication connections shown or discussed may be indirect couplings or communication connections through some interfaces, apparatuses, or units, or they may be electrical, mechanical, or other forms of connection.

[0091] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of the embodiments of the present invention, depending on actual needs.

[0092] Furthermore, the functional units in the various embodiments of the present invention can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit.

[0093] From the above description of the embodiments, those skilled in the art will clearly understand that the present invention can be implemented in hardware, firmware, or a combination thereof. When implemented in software, the above-described functions can be stored in a computer-readable medium or transmitted as one or more instructions or code on a computer-readable medium. Computer-readable media include computer storage media and communication media, wherein communication media include any medium that facilitates the transmission of a computer program from one place to another. Storage media can be any available medium accessible to a computer. For example, but not limited to, computer-readable media can include RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage media or other magnetic storage devices, or any other medium capable of carrying or storing desired program code having the form of instructions or data structures and accessible to a computer. Furthermore, any connection can suitably be a computer-readable medium. For example, if the software is transmitted from a website, server, or other remote source using coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL), or wireless technologies such as infrared, radio, and microwave, then coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, radio, and microwave are included in the definition of the medium. As used in this invention, disk and disc include compressed optical discs (CDs), laser discs, optical discs, digital versatile discs (DVDs), floppy disks, and Blu-ray discs, wherein disks typically magnetically copy data, while discs optically copy data using lasers. The combinations described above should also be included within the scope of protection for computer-readable media.

[0094] In summary, the above description is merely a preferred embodiment of the technical solution of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for coordinated optimization of photovoltaic, energy storage, and charging systems to extend transformer lifespan, characterized in that: The photovoltaic-storage-charging collaborative optimization method is applied to a photovoltaic-storage-charging distribution network that includes distribution transformers, photovoltaic power generation units, energy storage systems, charging loads, multiple feeder branches, and controlled distribution switches. The method includes: Collect the transformer thermal status, load current of each feeder branch, state of charge of the energy storage system, status of the distribution switch and priority of the load node of the photovoltaic-storage-charging-distribution network; The estimated value of the transformer winding hot spot temperature is determined based on the thermal state of the transformer and the load current of each feeder branch, and the distribution transformer is judged to be in a thermal overload state based on the estimated value of the winding hot spot temperature. When the distribution transformer is in a thermal overload state, a trip control signal is output to the corresponding controlled distribution switch according to the load node priority and the load current of each feeder branch to disconnect the non-critical load branch. Obtain the transformer heat dissipation trend after the non-critical load branch is disconnected, and form a candidate restoration access scheme based on the load current increment of the high priority load to be restored, the address of the distribution switch and the transformer heat dissipation trend; The thermal safety margin is checked for the predicted highest winding hot spot temperature corresponding to the candidate recovery access scheme. If the check fails and the energy storage system has the discharge support capability, the discharge power setting value is output to the power conversion unit of the energy storage system, and the thermal safety margin is checked again based on the equivalent load current after the energy storage system discharges. After passing the thermal safety margin check, the corresponding controlled power distribution switches are closed step by step according to the corresponding candidate restoration access scheme. During the closing process, the subsequent restoration access actions are suspended, delayed or reverted based on the real-time thermal status of the transformer and the feedback of the feeder branch load current.

2. The photovoltaic-storage-charging collaborative optimization method according to claim 1, characterized in that, The acquisition of transformer thermal status, load current of each feeder branch, state of charge of the energy storage system, status of distribution switches, and load node priority of the photovoltaic-storage-charging-distribution network includes: The top oil temperature is obtained by a temperature probe installed at the oil temperature measurement location of the distribution transformer, the ambient temperature is obtained by an ambient temperature sensor, the load current of each feeder branch is obtained by a current transformer, the bus voltage is obtained by a voltage transformer, the opening and closing status of the controlled distribution switch is obtained by a switch quantity acquisition terminal, and the state of charge and allowable discharge status of the energy storage system are read by the communication interface of the battery management unit.

3. The photovoltaic-storage-charging collaborative optimization method according to claim 1, characterized in that, The step of determining the estimated value of the transformer winding hot spot temperature based on the transformer thermal state and the load current of each feeder branch includes: Using the top oil temperature and ambient temperature measured on-site as the thermal state basis, the load rate calculated from the load current of each feeder branch as the heat generation intensity input, and combined with the transformer rated current, rated winding temperature rise and thermal model index calibrated during system initialization or maintenance, the estimated value of the winding hot spot temperature is obtained.

4. The photovoltaic-storage-charging collaborative optimization method according to claim 1, characterized in that: The priority of the load node is determined by at least one of the following: power supply guarantee level, load type, historical electricity consumption statistics record, and operation and maintenance configuration table. The non-critical load branches include feeder branches with a priority lower than the preset priority boundary and that do not belong to continuous production, emergency power supply or safety assurance loads.

5. The photovoltaic-storage-charging collaborative optimization method according to claim 1, characterized in that, The step of outputting a trip control signal to the corresponding controlled distribution switch based on the load node priority and the load current of each feeder branch includes: First, screen the non-critical load branches, then determine the disconnection sequence in the non-critical load branches according to the current feeder branch load current from large to small, and output a trip control signal to at least one of the circuit breaker, contactor or solid-state relay.

6. The photovoltaic-storage-charging collaborative optimization method according to claim 1, characterized in that, The process of obtaining the transformer heat dissipation trend after the non-critical load branch is disconnected includes: Within the monitoring window after the non-critical load branch is disconnected, the top oil temperature, the estimated winding hot spot temperature, and the feeder branch load current are continuously collected. The heat dissipation trend slope of the estimated winding hot spot temperature over time within the monitoring window is calculated, and the heat dissipation trend slope of the transformer is used to characterize the heat dissipation trend of the transformer.

7. The photovoltaic-storage-charging collaborative optimization method according to claim 1, characterized in that: The candidate recovery access scheme includes the high-priority load branch to be restored, the proposed closing time, the corresponding controlled power distribution switch address, the load current increment to be restored, and the candidate access interval; The candidate access interval is dynamically determined based on the transformer's heat dissipation trend, the current winding hot spot temperature estimate, the thermal safety threshold, and the temperature fluctuation safety margin.

8. The photovoltaic-storage-charging collaborative optimization method according to claim 1, characterized in that, The energy storage system having discharge support capability means that the energy storage system's state of charge is higher than the discharge lower limit, the power conversion unit is in an available state, the allowable discharge duration meets the support duration required by the candidate recovery access scheme, and the available output power of the power conversion unit can cover at least a portion of the load power to be supported by the high priority load to be restored.

9. The photovoltaic-storage-charging collaborative optimization method according to claim 1, characterized in that, The process of pausing, delaying, or reversing subsequent connection restoration actions based on real-time transformer thermal status and feeder branch load current feedback includes: If, after any controlled power distribution switch is closed, the estimated value of the winding hot spot temperature reaches or exceeds the recovery closing judgment boundary formed by subtracting the temperature fluctuation safety margin from the thermal safety threshold, the temperature rise rate exceeds the temperature rise deviation threshold, the feeder branch load current suddenly increases, or the energy storage system discharge state is abnormal, then the subsequent closed controllable power distribution switch is suspended, and the heat dissipation trend acquisition or non-critical load unloading steps are re-entered.

10. A photovoltaic-storage-charging collaborative optimization system for extending transformer lifespan, characterized in that, The photovoltaic-storage-charging collaborative optimization system includes: The status acquisition module is used to collect the transformer thermal status, load current of each feeder branch, energy storage system charge status, distribution switch status and load node priority of the photovoltaic-storage-charging-distribution network. The thermal overload identification module is used to determine the estimated value of the winding hot spot temperature of the distribution transformer based on the thermal state of the transformer and the load current of each feeder branch, and to identify whether the distribution transformer is in a thermal overload state. The non-critical load disconnection module is used to control the corresponding controlled distribution switch to disconnect the non-critical load branch when the distribution transformer is detected to be in a thermal overload state, based on the load node priority and the load current of each feeder branch. The candidate recovery access scheme forming module is used to form candidate recovery access schemes based on the transformer heat dissipation trend after the non-critical load branch is disconnected, the load current increment of the high priority load to be restored, and the address of the distribution switch, and to perform thermal safety margin verification on the candidate recovery access schemes. The energy storage system support verification module is used to determine whether the energy storage system has discharge support capability when the candidate recovery access scheme fails the thermal safety margin verification. If it has discharge support capability, it outputs a discharge power setting value to the power conversion unit of the energy storage system and re-verifies the thermal safety margin based on the equivalent load current after the energy storage system discharges. The recovery execution feedback module is used to close the corresponding controlled power distribution switch step by step according to the candidate recovery access scheme when the candidate recovery access scheme passes the thermal safety margin check, and to suspend, delay or roll back the subsequent recovery access actions based on the real-time transformer thermal status and feeder branch load current feedback.

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