A method and system for mutual power adjustment between power distribution stations

Abstract

This invention belongs to the field of AC / DC distribution network and microgrid technology, and discloses a method and system for mutual power assistance between distribution transformer areas. The method includes: calculating the load rate of the distribution transformer based on its active power, and setting the direction of active power flow to obtain the load status of each distribution transformer area; calculating the total overload power of all forward-loaded and reverse-loaded distribution transformer areas to obtain the overload power status of each area, and establishing a preliminary power allocation strategy; allocating the overload power of the overloaded distribution transformer areas, and allocating the remaining overload power to adjacent distribution transformer areas based on the principle of proximity by electrical distance; setting the charging and discharging power of a DC energy storage device based on a threshold condition where the load rate of all distribution transformer areas has reached a certain threshold, and adjusting the active power of the AC distribution transformer areas through the charging and discharging operation of the DC energy storage device. This invention effectively solves the problem of reverse overload of distribution transformers caused by distributed power backflow.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of AC / DC power distribution network and micro-grid, and particularly relates to a power mutual assistance method and system for a transformer area. BACKGROUND

[0002] With the rapid development of renewable energy, distributed photovoltaic power generation has been widely used in rural areas in China. According to statistics, more than 95% of distributed photovoltaic power is connected to the rural low-voltage distribution network, providing clean and sustainable energy supply for rural areas. However, the power load in rural areas is generally low, and the photovoltaic power generation capacity often exceeds the local power demand during the day, resulting in a large amount of power being sent back to the distribution network, causing reverse overload or overload of the distribution transformer. At the same time, some transformer areas in rural areas also have power loads such as small factories and irrigation wells, and the power consumption is large in some time periods, further aggravating the imbalance of the distribution network load. To solve these problems, transformer area power mutual assistance technology, especially low-voltage flexible DC interconnection technology, has gradually attracted attention. It establishes a DC interconnection network on the low-voltage side to realize flexible power allocation between multiple distribution transformer areas, providing a new idea for solving the problem of photovoltaic power return and load imbalance.

[0003] However, the existing transformer area power mutual assistance technology still has some deficiencies. First, most methods lack real-time accurate calculation of the load rate of the distribution transformer and timely judgment of the heavy overload condition, resulting in insufficient pertinence of power allocation. Second, the existing power distribution strategy is often too simple and fails to fully consider the priority of forward and reverse heavy overload and the influence of electrical distance on power distribution, making it difficult to achieve optimal power mutual assistance effect. In addition, the existing methods generally lack an integrated intelligent decision system, which cannot automatically execute the optimal power mutual assistance strategy according to real-time conditions.

[0004] Therefore, how to provide a solution to the problem of reverse heavy overload of the distribution transformer caused by the return of distributed power source power has become a problem to be solved at present. SUMMARY

[0005] The embodiment of the present application provides a transformer area power mutual assistance method and system, which redistributes the low-voltage distribution area power through an AC / DC conversion device to solve the problem of reverse heavy overload of the distribution transformer caused by the return of distributed power source power in the prior art.

[0006] The following presents a simplified summary of some aspects of the disclosed embodiments in order to provide a basic understanding of such embodiments. This summary is not an extensive overview of the embodiments described in this disclosure and is intended neither to identify key or critical elements of all embodiments nor to delineate the scope of any of the embodiments. Its sole purpose is to present some concepts in a simplified form as a prelude to the more detailed description that is presented later.

[0007] According to a first aspect of an embodiment of the present application, a power mutual assistance method for a transformer area is provided.

[0008] In one embodiment, the power mutual assistance method for the transformer area comprises:

[0009] According to the active power of the distribution transformer, in combination with the capacity of the distribution transformer, the load rate of the distribution transformer is calculated, and the active power flow direction of the distribution transformer is set to obtain the load condition of each transformer area;

[0010] Based on the load condition of each transformer area, it is determined whether there is a heavy overload transformer area, and the total overload power of all forward heavy overload transformer areas and the total overload power of reverse heavy overload transformer areas are calculated to obtain the overload power condition of each transformer area, and a preliminary power distribution strategy is established;

[0011] According to the preliminary power distribution strategy, the overload power of the heavy overload transformer area is distributed, and the remaining overload power is distributed to the adjacent transformer area based on the principle of proximity according to the electrical distance, until there is no heavy overload transformer area or the load rate of all transformer areas reaches the threshold condition;

[0012] Based on the threshold condition that the load rate of all transformer areas reaches, the charge and discharge power of the direct current energy storage device is set, and the active power of the alternating current transformer area is adjusted through the charge and discharge operation of the direct current energy storage device.

[0013] In one embodiment, according to the active power of the distribution transformer, in combination with the capacity of the distribution transformer, the load rate of the distribution transformer is calculated to obtain the load condition of each transformer area, and the active power flow direction of the distribution transformer is set to include:

[0014] Based on all transformer areas, real-time data of the distribution transformer is collected to obtain the active power of the distribution transformer;

[0015] The active power of the distribution transformer is used in combination with the capacity of the distribution transformer to calculate the load rate of the distribution transformer;

[0016] According to the load rate of the distribution transformer, the active power flow direction of the distribution transformer is set to determine the power flow direction of each transformer area.

[0017] In one embodiment, the calculation expression of the load rate of the distribution transformer is:

[0018]

[0019] In the formula, λ i represents the load rate of the distribution transformer of the transformer area i, P i represents the active power of the distribution transformer of the transformer area i, S i represents the capacity of the distribution transformer of the transformer area i;

[0020] The active power flow of the distribution transformer is set as: the active power of the distribution transformer flows from the medium-voltage distribution network to the low-voltage distribution network as positive.

[0021] In one embodiment, the calculation expression of the total excess power of all positive heavy overload substation areas is:

[0022]

[0023] In the formula, P Σ+ represents the sum of the excess power of all positive heavy overload substation areas, λ max represents the positive heavy overload load rate threshold of the substation area.

[0024] The calculation expression of the total excess power of all negative heavy overload substation areas is:

[0025]

[0026] In the formula, P Σ- represents the sum of the excess power of all negative heavy overload substation areas, λ min represents the negative heavy overload load rate threshold of the substation area.

[0027] In one embodiment, according to the preliminary power distribution strategy, the excess power of the heavy overload substation area is distributed, and the remaining excess power is distributed to the adjacent substation area based on the principle of proximity according to the electrical distance, until there is no heavy overload substation area or the load rate of all substation areas reaches the threshold condition, including:

[0028] According to the preliminary power distribution strategy, the excess power of the heavy overload substation area is distributed, and the remaining excess power is reserved.

[0029] When there is no negative heavy overload substation area, the remaining excess power of the positive heavy overload substation area is distributed to the adjacent substation area based on the principle of proximity according to the electrical distance, until there is no positive heavy overload substation area or the load rate of all substation areas reaches the positive heavy overload load rate threshold.

[0030] When there is no positive heavy overload substation area, the remaining excess power of the negative heavy overload substation area is distributed to the adjacent substation area based on the principle of proximity according to the electrical distance, until there is no negative heavy overload substation area or the load rate of all substation areas reaches the negative heavy overload load rate threshold.

[0031] In one embodiment, according to the preliminary power distribution strategy, the excess power of the heavy overload substation area is distributed, and the remaining excess power is reserved, including:

[0032] Comparing the total excess power of the positive heavy overload substation area with the total excess power of the negative heavy overload substation area.

[0033] When the total over-limit power of the forward heavy overload substation area is greater than the total over-limit power of the reverse heavy overload substation area, the over-limit power of the forward over-limit substation area is preferentially allocated to the reverse over-limit substation area until there is no reverse heavy overload substation area, and the remaining over-limit power is reserved;

[0034] When the total over-limit power of the forward heavy overload substation area is less than or equal to the total over-limit power of the reverse heavy overload substation area, the over-limit power of the reverse over-limit substation area is preferentially allocated to the forward over-limit substation area until there is no forward heavy overload substation area, and the remaining over-limit power is reserved.

[0035] In one embodiment, the condition that all substation load rates reach a threshold value includes two cases: all substation load rates reach a forward heavy load rate threshold value and all substation load rates reach a reverse heavy load rate threshold value.

[0036] In one embodiment, based on the threshold condition that all substation load rates reach, the charge and discharge power of the direct current energy storage device is set, and the active power of the alternating current substation is adjusted through the charge and discharge operation of the direct current energy storage device, which includes:

[0037] When all substation load rates reach the forward heavy load rate threshold value, the total over-limit power of the forward heavy overload substation area is compared with the maximum discharge power of the direct current energy storage device, and the discharge power of the direct current energy storage device is determined based on the comparison result, and the active power of the alternating current substation is supplied through the discharge operation of the direct current energy storage device;

[0038] When all substation load rates reach the reverse heavy load rate threshold value, the total over-limit power of the reverse heavy overload substation area is compared with the maximum charge power of the direct current energy storage device, and the charge power of the direct current energy storage device is determined based on the comparison result, and the active power of the alternating current substation is absorbed through the charge operation of the direct current energy storage device.

[0039] According to a second aspect of the embodiment of the present application, a substation power mutual aid system is provided.

[0040] In one embodiment, the substation power mutual aid system includes an alternating current-direct current conversion device, a direct current interconnection line, a direct current energy storage device, and a fusion terminal.

[0041] The alternating current-direct current conversion device is configured in each substation, and the alternating current side of the alternating current-direct current conversion device is connected to the low-voltage bus of the corresponding substation.

[0042] The direct current interconnection line is used to connect the direct current side of the alternating current-direct current conversion device of each substation.

[0043] The direct current energy storage device is used to adjust the active power of the alternating current substation through charge and discharge operation.

[0044] The fusion terminal is used for collecting active power of distribution transformers, analyzing load conditions and over-limit power conditions of each area, establishing a preliminary power distribution strategy, and generating corresponding control instructions, and the corresponding control instructions are sent to the AC-DC conversion device.

[0045] In one embodiment, the fusion terminal includes a load rate analysis unit, an over-limit power judgment unit, a power distribution and optimization unit, and an energy storage adjustment unit.

[0046] The load rate analysis unit is configured to calculate the load rate of the distribution transformer based on the active power of the distribution transformer and the capacity of the distribution transformer, and set the active power flow direction of the distribution transformer to obtain the load condition of each area.

[0047] The over-limit power judgment unit is configured to determine whether there is a heavy overload area based on the load condition of each area, calculate the total over-limit power of all forward heavy overload areas and the total over-limit power of all reverse heavy overload areas, obtain the over-limit power condition of each area, and establish a preliminary power distribution strategy.

[0048] The power distribution and optimization unit is configured to distribute the over-limit power of the heavy overload area according to the preliminary power distribution strategy, and distribute the remaining over-limit power to the adjacent area based on the principle of proximity according to the electrical distance, until there is no heavy overload area or the load rate of all areas reaches the threshold condition.

[0049] The energy storage adjustment unit is configured to set the charge and discharge power of the DC energy storage device based on the threshold condition that the load rate of all areas reaches, and adjust the active power of the AC area through the charge and discharge operation of the DC energy storage device.

[0050] In one embodiment, the load rate analysis unit includes an active power collection module, a load rate calculation module, and a power flow direction module.

[0051] The active power collection module is configured to collect real-time data of the distribution transformer based on all areas to obtain the active power of the distribution transformer.

[0052] The load rate calculation module is configured to calculate the load rate of the distribution transformer based on the active power of the distribution transformer and the capacity of the distribution transformer.

[0053] The power flow direction module is configured to set the active power flow direction of the distribution transformer based on the load rate of the distribution transformer to determine the power flow direction of each area.

[0054] In one embodiment, the calculation expression of the load rate of the distribution transformer is as follows:

[0055]

[0056] In the formula, λ irepresents the load rate of the distribution transformer of the substation i, P i represents the active power of the distribution transformer of the substation i, S i represents the capacity of the distribution transformer of the substation i;

[0057] The active power flow of the distribution transformer is set as: the active power of the distribution transformer flowing from the medium-voltage distribution network to the low-voltage distribution network is positive.

[0058] In one embodiment, the power distribution and optimization unit comprises a preliminary power distribution module, a forward heavy overload optimization module and a reverse heavy overload optimization module.

[0059] The preliminary power distribution module is configured to distribute the excess power of the heavy overload substations based on a preliminary power distribution strategy, and reserve the remaining excess power.

[0060] The forward heavy overload optimization module is configured to, when there is no reverse heavy overload substation, distribute the remaining excess power of the forward heavy overload substations to the adjacent substations according to the principle of proximity based on electrical distance, until there is no forward heavy overload substation, or the load rates of all substations reach the forward heavy overload load rate threshold.

[0061] The reverse heavy overload optimization module is configured to, when there is no forward heavy overload substation, distribute the remaining excess power of the reverse heavy overload substations to the adjacent substations according to the principle of proximity based on electrical distance, until there is no reverse heavy overload substation, or the load rates of all substations reach the reverse heavy overload load rate threshold.

[0062] In one embodiment, the preliminary power distribution module comprises an excess power comparison module, a forward preferential distribution module and a reverse preferential distribution module.

[0063] The excess power comparison module is configured to compare the total excess power of the forward heavy overload substations with the total excess power of the reverse heavy overload substations.

[0064] The forward preferential distribution module is configured to, when the total excess power of the forward heavy overload substations is greater than the total excess power of the reverse heavy overload substations, preferentially distribute the excess power of the forward heavy overload substations to the reverse heavy overload substations, until there is no reverse heavy overload substation, and reserve the remaining excess power.

[0065] The reverse preferential distribution module is configured to, when the total excess power of the forward heavy overload substations is less than or equal to the total excess power of the reverse heavy overload substations, preferentially distribute the excess power of the reverse heavy overload substations to the forward heavy overload substations, until there is no forward heavy overload substation, and reserve the remaining excess power.

[0066] In one embodiment, the condition that the load rates of all substations reach the threshold includes two cases: the load rates of all substations reach the forward heavy overload load rate threshold and the load rates of all substations reach the reverse heavy overload load rate threshold.

[0067] In one embodiment, the energy storage regulating unit comprises a forward overload control module and a reverse overload control module.

[0068] The forward overload control module is configured to compare the total overload power of the forward overload area with the maximum discharging power of the DC energy storage device when the load rate of all areas reaches the forward overload threshold, and determine the discharging power of the DC energy storage device based on the comparison result, and supply the active power of the AC area through the discharging operation of the DC energy storage device.

[0069] The reverse overload control module is configured to compare the total overload power of the reverse overload area with the maximum charging power of the DC energy storage device when the load rate of all areas reaches the reverse overload threshold, and determine the charging power of the DC energy storage device based on the comparison result, and absorb the active power of the AC area through the charging operation of the DC energy storage device.

[0070] According to a third aspect of the embodiments of the present application, a computer device is provided.

[0071] In one embodiment, the computer device comprises a memory and a processor, the memory stores a computer program, and the processor executes the computer program to implement the steps of the above method.

[0072] According to a fourth aspect of the embodiments of the present application, a computer readable storage medium is provided.

[0073] In one embodiment, the computer readable storage medium stores a computer program, and the computer program is executed by a processor to implement the steps of the above method.

[0074] The technical scheme provided by the embodiments of the present application can include the following beneficial effects:

[0075] (1) The present application redistributes the power of the low-voltage distribution area through the AC-DC converter, effectively solves the problem of reverse overload and overload of the distribution transformer caused by the return of distributed power, not only improves the operation safety of the distribution network, but also provides technical support for large-scale access of distributed energy; at the same time, the present application accurately calculates the load rate of each area by real-time monitoring and analyzing the active power data of the distribution transformer, and determines the overload condition according to the preset threshold, which provides an accurate data basis for power mutual aid; by establishing a preliminary power distribution strategy, intelligent power distribution between overloaded areas is realized, and the remaining power is reasonably distributed according to the principle of proximity of electrical distance, effectively alleviating the load imbalance problem between areas.

[0076] (2) The application further adjusts the active power of the AC area by intelligently controlling the charging and discharging operation of the energy storage device when there is still over-limit power after power distribution, realizes more fine and flexible load balancing, and in addition, the introduction of the fusion terminal enables the entire system to have intelligent analysis and decision-making capabilities, can automatically execute the optimal power mutual aid strategy according to real-time conditions, not only improves the operation efficiency and reliability of the distribution network, but also provides an innovative solution for flexible access and efficient consumption of distributed energy, and has important practical significance and popularization value for building a more intelligent, flexible and safe modern distribution network.

[0077] It should be understood that the foregoing general description and the following detailed description are only exemplary and explanatory, and cannot limit the application. BRIEF DESCRIPTION OF DRAWINGS

[0078] The accompanying drawings incorporated in and forming a part of the specification illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the application.

[0079] Figure 1 is a flowchart of a power mutual aid method for a transformer area according to an exemplary embodiment;

[0080] Figure 2 is a basic element schematic diagram of a power mutual aid system for a transformer area according to an exemplary embodiment;

[0081] Figure 3 is a detailed implementation diagram of a power mutual aid method for a transformer area according to an exemplary embodiment;

[0082] Figure 4 is an application example diagram of a power mutual aid system for a transformer area in a certain village in a certain place according to an exemplary embodiment;

[0083] Figure 5 is a transmission power curve diagram of three AC-DC conversion devices on a certain day after the application of a power mutual aid system for a transformer area in a certain village in a certain place according to an exemplary embodiment;

[0084] Figure 6 is a structural block diagram of a power mutual aid system for a transformer area according to an exemplary embodiment;

[0085] Figure 7 is a structural schematic diagram of a computer device according to an exemplary embodiment. DETAILED DESCRIPTION

[0086] The following description and drawings are illustrative of specific embodiments thereof and are not intended to limit the scope of the embodiments. Parts and features of some embodiments can be included or substituted in or for parts and features of other embodiments. The scope of the embodiments encompassed herein includes the whole scope of the claims together with all available equivalents of the claims. In this document, the terms "first", "second", etc. are used merely to distinguish one element from another, and do not require or imply any actual relationship or order between the elements. In fact, the first element could be called the second element, and vice versa. Also, the terms "comprises", "comprising", or any other variations thereof are intended to cover a non-exclusive inclusion, such that a structure, device or apparatus that comprises a list of elements does not include only those elements but can also include other elements not expressly listed or inherent to such structure, device or apparatus. An element proceeded by "comprises... " does not, without more constraints, exclude the existence of additional identical elements in the structure, device or apparatus that includes the element. Various embodiments are described in progressive stages, each of which focuses on the differences from other embodiments, and the same or similar parts between various embodiments can be referred to each other.

[0087] The terms "longitudinal", "lateral", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer" and the like as used herein to indicate orientation or positional relationships based on the orientations or positional relationships shown in the drawings, are only intended to facilitate the description herein and simplify the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application. In the description herein, unless otherwise specified and limited, the terms "mount", "connect", "connection" should be interpreted broadly, for example, it can be a mechanical connection or an electrical connection, it can be a communication between two elements inside, it can be a direct connection or an indirect connection through an intermediate medium, and the specific meaning of the above terms can be understood by the person skilled in the art according to the specific circumstances.

[0088] In this document, the term "multiple" means two or more, unless otherwise specified.

[0089] In this document, the character " / " represents an "or" relationship between the objects before and after it. For example, A / B means: A or B.

[0090] In this document, the term "and / or" is a description of the relationship between the objects, which means that there can be three relationships. For example, A and / or B means: A or B, or, A and B, the three relationships.

[0091] It should be understood that although the steps in the flowchart are shown in sequential order, such that each step is performed after another, the steps are not necessarily performed in the order shown by the arrows. Unless specifically stated in this document, the steps are not necessarily performed in the order shown, and the steps can be performed in other orders. Moreover, at least some of the steps in the figure can include multiple sub-steps or multiple stages, which are not necessarily performed at the same time, and which can be performed at different times, and which can be performed in different orders, and which can be performed alternately or alternately with at least some of the steps or sub-steps or stages of other steps.

[0092] The various modules in the device or system of the present application can be implemented in whole or in part by software, hardware and their combination. The above modules can be embedded in or independent of the processor in the computer device in hardware form, or stored in the memory in the computer device in software form, so as to be called and executed by the processor to perform the operations corresponding to the above modules.

[0093] In the case of no conflict, the embodiments in the present application and the features in the embodiments can be combined with each other.

[0094] Figure 1 With Figure 3 An embodiment of a power mutual assistance method for a transformer area of the present application is shown.

[0095] In this optional embodiment, the power mutual assistance method for the transformer area comprises:

[0096] Step S101, according to the active power of the distribution transformer, combining the capacity of the distribution transformer, the load rate of the distribution transformer is calculated, and the active power flow direction of the distribution transformer is set, to obtain the load condition of each transformer area;

[0097] Specifically, as shown in Figure 3 The specific implementation process of the power mutual assistance method for the transformer area based on low-voltage flexible DC interconnection is shown in the figure. ① Collect the active power of the distribution transformer; ② Calculate the load rate of the distribution transformer.

[0098] It should be noted that in a power system, when the load of a distribution area is close to its rated capacity, it is called a heavy load; when the load of a distribution area exceeds its rated capacity, it is called an overload. In this embodiment, distribution areas are divided into three types according to their load conditions: heavily overloaded distribution areas, normally loaded distribution areas, and unloaded distribution areas. Among them, heavily overloaded distribution areas include both heavy load and overloaded distribution areas. Heavy load distribution areas refer to distribution areas whose load rate exceeds the rated range (set to 80% in this embodiment), overloaded distribution areas refer to distribution areas whose load rate exceeds 100%, normally loaded distribution areas refer to distribution areas whose load rate is within the rated range, and unloaded distribution areas refer to distribution areas whose load rate is 0. Normal load distribution areas and unloaded distribution areas are in normal working or non-working states and are not the situations discussed in this invention. This invention mainly focuses on the heavily overloaded distribution areas, which are most likely to experience safety accidents.

[0099] Step S103: Based on the load conditions of each distribution area, determine whether there are any heavily overloaded distribution areas, and calculate the total over-limit power of all forward heavily overloaded distribution areas and the total over-limit power of reverse heavily overloaded distribution areas to obtain the over-limit power situation of each distribution area and establish a preliminary power allocation strategy.

[0100] Specifically, step ③ determines whether there is a forward or reverse overloaded distribution transformer area. If such an area exists, proceed to step ④; otherwise, power mutual assistance between distribution transformer areas is not performed. In this embodiment, a distribution transformer area where the active power flow of the distribution transformer is in the forward direction is called a forward overloaded distribution transformer area, and a distribution transformer area where the active power flow of the distribution transformer is in the reverse direction is called a reverse overloaded distribution transformer area. The forward overload rate threshold for the distribution transformer area is preset to 80%, and the reverse overload rate threshold is preset to -80%. These thresholds can also be manually specified according to actual on-site control requirements. For example, if it is not desired that the distribution transformer will experience power reverse transmission, the reverse overload rate threshold for the distribution transformer area can be specified as 0%.

[0101] Specifically, ④ calculate the sum of the over-limit power of all positive heavy overload areas to obtain the total over-limit power P of the positive heavy overload areas. Σ+ ⑤ Calculate the sum of the over-limit power of all reverse heavy overload areas to obtain the total over-limit power P of the reverse heavy overload areas. Σ- .

[0102] Step S105: According to the preliminary power allocation strategy, allocate the overloaded power of the heavy overloaded transformer area, and allocate the remaining overloaded power to the adjacent transformer area based on the principle of proximity of electrical distance, until there are no heavy overloaded transformer areas or the load rate of all transformer areas reaches the threshold condition.

[0103] Step S107: Based on the threshold condition that the load rate of all transformer areas has reached the threshold, set the charging and discharging power of the DC energy storage device, and adjust the active power of the AC transformer area through the charging and discharging operation of the DC energy storage device.

[0104] Specifically, ⑥ if P Σ+ >PΣ- :

[0105] 1) Prioritize the excess power of the forward overload area to the reverse overload area until there is no reverse overload area, at which time, P Σ+ = P Σ+ -P Σ- , P Σ- = 0.

[0106] 2) According to the principle of proximity in electrical distance, the excess power of the forward overload area is allocated to the adjacent area until there is no forward overload area, or the load rate of all areas reaches the forward overload load rate threshold, at which time P Σ+ = 0 or λ i ≥ λ max (i = 1, 2, 3,..., n, n represents the number of areas connected by the low-voltage flexible DC interconnection system).

[0107] 3) If the load rate of all areas reaches the forward overload load rate threshold, i.e. λ i≥ λ max (i = 1, 2, 3,..., n), the DC energy storage device is discharged to supply active power to the AC area; if the maximum discharge power of the DC energy storage device is greater than P Σ+ , then the discharge power of the DC energy storage device is set to P Σ+ , otherwise the DC energy storage device discharges at the maximum power.

[0108] Specifically, if P Σ+ ≤ P Σ— :

[0109] 1) Prioritize the excess power of the reverse overload area to the forward overload area until there is no forward overload area, at which time, P Σ- = P Σ- -P Σ+ , P Σ+ = 0.

[0110] 2) According to the principle of proximity in electrical distance, the excess power of the reverse overload area is allocated to the adjacent area until there is no reverse overload area, or the load rate of all areas reaches the reverse overload load rate threshold, at which time P Σ- = 0 or λ i ≤ λ min (i = 1, 2, 3,..., n, n represents the number of areas connected by the low-voltage flexible DC interconnection system).

[0111] 3) If the load rate of all areas reaches the reverse overload load rate threshold, i.e. λ i ≤ λ min(i = 1, 2, 3, …, n), the direct current energy storage device is charged to absorb active power from the alternating current area; if the maximum charging power of the direct current energy storage device is greater than P Σ- , the charging power of the direct current energy storage device is set to P Σ- , otherwise the direct current energy storage device is charged at the maximum power.

[0112] In this alternative embodiment, according to the active power of the distribution transformer, the load rate of the distribution transformer is calculated in combination with the capacity of the distribution transformer to obtain the load condition of each area, and the active power flow direction of the distribution transformer is set to include:

[0113] Step S1011, based on all areas, real-time data of the distribution transformer is collected respectively to obtain the active power of the distribution transformer;

[0114] Step S1013, the active power of the distribution transformer is used to calculate the load rate of the distribution transformer in combination with the capacity of the distribution transformer;

[0115] Step S1015, according to the load rate of the distribution transformer, the active power flow direction of the distribution transformer is set to determine the power flow direction of each area.

[0116] In this alternative embodiment, the calculation expression of the load rate of the distribution transformer is:

[0117]

[0118] In the formula, λ i represents the load rate of the distribution transformer of area i, P i represents the active power of the distribution transformer of area i, S i represents the capacity of the distribution transformer of area i.

[0119] The active power flow direction of the distribution transformer is set as: the active power of the distribution transformer flows from the medium voltage distribution network to the low voltage distribution network as positive.

[0120] Specifically, since each distribution area is equipped with distributed power supply and power load, the power of the distribution transformer may flow in both directions; in this embodiment, the power flowing from 10kV to 380V is defined as positive, and the power flowing from 380V to 10kV is defined as negative.

[0121] In this alternative embodiment, the calculation expression of the total over-limit power of all positive forward overload areas is:

[0122]

[0123] In the formula, P Σ+ represents the sum of the over-limit power of all positive forward overload areas, λ maxa forward overload load rate threshold of the substation;

[0124] The calculation expression of the total excess power of all reverse overload substation is:

[0125]

[0126] wherein, P Σ- represents the sum of the excess power of all reverse overload substation, λ min represents a reverse overload load rate threshold of the substation.

[0127] In the optional embodiment, the excess power of the overload substation is allocated according to the preliminary power allocation strategy, and the remaining excess power is allocated to the adjacent substation based on the principle of proximity according to the electrical distance, until there is no overload substation or all substation load rates reach the threshold condition, including:

[0128] Step S1051, allocating the excess power of the overload substation based on the preliminary power allocation strategy, and reserving the remaining excess power;

[0129] Step S1053, when there is no reverse overload substation, allocating the remaining excess power of the forward overload substation to the adjacent substation based on the principle of proximity according to the electrical distance, until there is no forward overload substation or all substation load rates reach the forward overload load rate threshold;

[0130] Step S1055, when there is no forward overload substation, allocating the remaining excess power of the reverse overload substation to the adjacent substation based on the principle of proximity according to the electrical distance, until there is no reverse overload substation or all substation load rates reach the reverse overload load rate threshold.

[0131] Specifically, the preliminary power allocation strategy includes: if there is no reverse overload substation, allocating the remaining excess power of the forward overload substation to the adjacent substation based on the principle of proximity according to the electrical distance, until there is no forward overload substation or all substation load rates reach the forward overload load rate threshold; if there is no forward overload substation, allocating the remaining excess power of the reverse overload substation to the adjacent substation based on the principle of proximity according to the electrical distance, until there is no reverse overload substation or all substation load rates reach the reverse overload load rate threshold.

[0132] In the optional embodiment, allocating the excess power of the overload substation based on the preliminary power allocation strategy, and reserving the remaining excess power includes:

[0133] Comparing the total excess power of the forward overload substation with the total excess power of the reverse overload substation;

[0134] When the total over-limit power of the forward heavy overload substation area is greater than the total over-limit power of the reverse heavy overload substation area, the over-limit power of the forward over-limit substation area is preferentially allocated to the reverse over-limit substation area until there is no reverse heavy overload substation area, and the remaining over-limit power is reserved;

[0135] When the total over-limit power of the forward heavy overload substation area is less than or equal to the total over-limit power of the reverse heavy overload substation area, the over-limit power of the reverse over-limit substation area is preferentially allocated to the forward over-limit substation area until there is no forward heavy overload substation area, and the remaining over-limit power is reserved.

[0136] In this optional embodiment, the condition that all substation load rates reach a threshold value includes two cases: all substation load rates reach a forward heavy load rate threshold value and all substation load rates reach a reverse heavy load rate threshold value.

[0137] In this optional embodiment, based on the threshold condition that all substation load rates reach, the charge-discharge power of the direct-current energy storage device is set, and the active power of the alternating-current substation is adjusted through the charge-discharge operation of the direct-current energy storage device.

[0138] Step S1071, when all substation load rates reach the forward heavy load rate threshold value, the total over-limit power of the forward heavy overload substation area is compared with the maximum discharge power of the direct-current energy storage device, and the discharge power of the direct-current energy storage device is determined based on the comparison result, and the active power of the alternating-current substation is supplied through the discharge operation of the direct-current energy storage device;

[0139] Step S1073, when all substation load rates reach the reverse heavy load rate threshold value, the total over-limit power of the reverse heavy overload substation area is compared with the maximum charge power of the direct-current energy storage device, and the charge power of the direct-current energy storage device is determined based on the comparison result, and the active power of the alternating-current substation is absorbed through the charge operation of the direct-current energy storage device.

[0140] Figure 2 、 Figure 4 and Figure 6 An embodiment of a substation power mutual assistance system of the present application is shown.

[0141] In this optional embodiment, the substation power mutual assistance system includes an alternating-direct current conversion device, a direct-current interconnection line, a direct-current energy storage device, and a fusion terminal.

[0142] The alternating-direct current conversion device is configured in each substation, and the alternating side of the alternating-direct current conversion device is connected to the low-voltage bus of the corresponding substation.

[0143] The direct-current interconnection line is used to connect the direct-current side of the alternating-direct current conversion device of each substation.

[0144] The direct-current energy storage device is used to adjust the active power of the alternating-current substation through charge-discharge operation.

[0145] The fusion terminal is configured to collect active power of the power distribution transformer, analyze load conditions and over-limit power conditions of each area, establish a preliminary power distribution strategy, and generate corresponding control instructions, and the corresponding control instructions are sent to the AC-DC conversion device.

[0146] Specifically, as shown in Figure 2 , a power mutual assistance system of one area in the embodiment involves n power distribution areas, and each area is configured with an AC-DC conversion device C i (i = 1, 2,..., n), the AC side of C i is connected to the low-voltage bus of the power distribution area i, C1, C2... C n The DC side is connected through a DC interconnection line, and the DC energy storage device is directly connected or connected through a DC distribution cabinet. The low-voltage side of the power distribution area i is connected to a distributed power source S i and a load L i , so that the power distribution transformer T i may have bidirectional power flow. In the embodiment, power flow from 10kV to 380V is defined as forward, and power flow from 380V to 10kV is defined as reverse.

[0147] Specifically, in the above embodiment, the AC-DC conversion device C i adopts a three-level topology structure and has a DC voltage stabilization mode / constant active and reactive power mode switching function; the DC interconnection line voltage level is selected as 750V or ±375V.

[0148] Specifically, as shown in Figure 4 , the solid line in the figure represents the power line, and the dashed line represents the data flow. In the embodiment, the fusion terminal is responsible for collecting the active power of the power distribution transformer, the running state of the AC-DC conversion device, solving the area power mutual assistance method (including analyzing the load conditions and over-limit power conditions of each area, establishing a preliminary power distribution strategy, and generating corresponding control instructions), and sending the control instructions to the AC-DC conversion device. If the power mutual assistance system covers multiple areas, each area is configured with a fusion terminal, only the fusion terminal of a certain area is assigned the task of solving and executing the area power mutual assistance method. The fusion terminal aggregates the active power of the power distribution transformer, the running state of the AC-DC conversion device, the control instructions that have been sent, and other information, and uploads them to the cloud master station. The fusion terminal communicates with the AC-DC conversion device of the area through RS-485, and communicates with the AC-DC conversion device and the DC energy storage device of other areas through LoRa.

[0149] In this alternative embodiment, the fusion terminal includes a load rate analysis unit 201, an over-limit power judgment unit 203, a power distribution and optimization unit 205, and an energy storage adjustment unit 207.

[0150] The load rate analysis unit 201 is configured to calculate the load rate of the distribution transformer according to the active power of the distribution transformer and in combination with the capacity of the distribution transformer, and set the active power flow direction of the distribution transformer to obtain the load condition of each substation;

[0151] The overload power judgment unit 203 is configured to judge whether there is a heavy overload substation based on the load condition of each substation, calculate the total overload power of all forward heavy overload substations and the total overload power of all reverse heavy overload substations, obtain the overload power condition of each substation, and establish a preliminary power distribution strategy;

[0152] The power distribution and optimization unit 205 is configured to distribute the overload power of the heavy overload substation according to the preliminary power distribution strategy, and distribute the remaining overload power to the adjacent substations based on the principle of proximity according to the electrical distance until there is no heavy overload substation or the load rate of all substations reaches the threshold condition.

[0153] The energy storage adjustment unit 207 is configured to set the charge and discharge power of the direct-current energy storage device based on the threshold condition that the load rate of all substations reaches, and adjust the active power of the alternating-current substation through the charge and discharge operation of the direct-current energy storage device.

[0154] In this optional embodiment, the load rate analysis unit 201 includes an active power collection module, a load rate calculation module, and a power flow direction module.

[0155] The active power collection module (not shown in the figure) is configured to collect the real-time data of the distribution transformer based on all substations to obtain the active power of the distribution transformer.

[0156] The load rate calculation module (not shown in the figure) is configured to calculate the load rate of the distribution transformer by using the active power of the distribution transformer in combination with the capacity of the distribution transformer.

[0157] The power flow direction module (not shown in the figure) is configured to set the active power flow direction of the distribution transformer according to the load rate of the distribution transformer to determine the power flow direction of each substation.

[0158] In this optional embodiment, the calculation expression of the load rate of the distribution transformer is as follows:

[0159]

[0160] In the formula, λ i represents the load rate of the distribution transformer of the substation i, P i represents the active power of the distribution transformer of the substation i, S i represents the capacity of the distribution transformer of the substation i.

[0161] The active power flow of the distribution transformer is set as: the active power of the distribution transformer flows from the medium-voltage distribution network to the low-voltage distribution network as positive.

[0162] In the optional embodiment, the power distribution and optimization unit 205 comprises a preliminary power distribution module, a positive heavy overload optimization module and a negative heavy overload optimization module.

[0163] The preliminary power distribution module (not shown in the figure) is configured to distribute the excess power of the heavy overload area based on a preliminary power distribution strategy, and reserve the remaining excess power.

[0164] The positive heavy overload optimization module (not shown in the figure) is configured to distribute the remaining excess power of the positive heavy overload area to the adjacent area according to the principle of proximity based on the electrical distance until there is no positive heavy overload area or the load rate of all areas reaches the positive heavy overload load rate threshold.

[0165] The negative heavy overload optimization module (not shown in the figure) is configured to distribute the remaining excess power of the negative heavy overload area to the adjacent area according to the principle of proximity based on the electrical distance until there is no negative heavy overload area or the load rate of all areas reaches the negative heavy overload load rate threshold.

[0166] In the optional embodiment, the preliminary power distribution module comprises an excess power comparison module, a positive priority distribution module and a negative priority distribution module.

[0167] The excess power comparison module (not shown in the figure) is configured to compare the total excess power of the positive heavy overload area with the total excess power of the negative heavy overload area.

[0168] The positive priority distribution module (not shown in the figure) is configured to preferentially distribute the excess power of the positive heavy overload area to the negative heavy overload area when the total excess power of the positive heavy overload area is greater than the total excess power of the negative heavy overload area until there is no negative heavy overload area, and reserve the remaining excess power.

[0169] The negative priority distribution module (not shown in the figure) is configured to preferentially distribute the excess power of the negative heavy overload area to the positive heavy overload area when the total excess power of the positive heavy overload area is less than or equal to the total excess power of the negative heavy overload area until there is no positive heavy overload area, and reserve the remaining excess power.

[0170] In the optional embodiment, the condition that the load rate of all areas reaches the threshold value includes two cases: the load rate of all areas reaches the positive heavy overload load rate threshold and the load rate of all areas reaches the negative heavy overload load rate threshold.

[0171] In the optional embodiment, the energy storage regulating unit 207 comprises a forward overload control module and a reverse overload control module;

[0172] The forward overload control module (not shown in the figure) is configured to compare the total overload power of the forward overload area with the maximum discharge power of the DC energy storage device when the load rates of all areas reach the forward overload load rate threshold, and determine the discharge power of the DC energy storage device based on the comparison result, and supply the active power of the AC area through the discharge operation of the DC energy storage device.

[0173] The reverse overload control module (not shown in the figure) is configured to compare the total overload power of the reverse overload area with the maximum charge power of the DC energy storage device when the load rates of all areas reach the reverse overload load rate threshold, and determine the charge power of the DC energy storage device based on the comparison result, and absorb the active power of the AC area through the charge operation of the DC energy storage device.

[0174] In order to facilitate the understanding of the above technical solutions of the present application, the following will be described in detail as follows by taking the actual application of the present application in a certain village in a certain place as an example:

[0175] As shown in FIG. 1, the application example in the above-mentioned application example is shown in FIG. 2, wherein the power transmission of the three AC-DC conversion devices in the village during 7:00-17:40 on a certain day is shown, wherein the power of the two-area AC-DC conversion device is positive, indicating that the flexible DC system absorbs power from the two areas; the power of the 1st and 3rd area AC-DC conversion device is negative, indicating that the flexible DC system provides power to the 1st and 3rd areas; the sum of the power of the 1st, 2nd and 3rd area PCS is approximately 0, indicating that the power of the two areas is transferred to the 1st and 3rd areas, proving that the on-site consumption of distributed photovoltaic power during the day is completed by the present application, and the occurrence of reverse overload of the distribution transformer caused by the return of distributed photovoltaic power is avoided. Figure 4 As shown in FIG. 1, the application example in the above-mentioned application example is shown in FIG. 2, wherein the power transmission of the three AC-DC conversion devices in the village during 7:00-17:40 on a certain day is shown, wherein the power of the two-area AC-DC conversion device is positive, indicating that the flexible DC system absorbs power from the two areas; the power of the 1st and 3rd area AC-DC conversion device is negative, indicating that the flexible DC system provides power to the 1st and 3rd areas; the sum of the power of the 1st, 2nd and 3rd area PCS is approximately 0, indicating that the power of the two areas is transferred to the 1st and 3rd areas, proving that the on-site consumption of distributed photovoltaic power during the day is completed by the present application, and the occurrence of reverse overload of the distribution transformer caused by the return of distributed photovoltaic power is avoided.

[0176] Figure 5 As shown in FIG. 1, the application example in the above-mentioned application example is shown in FIG. 2, wherein the power transmission of the three AC-DC conversion devices in the village during 7:00-17:40 on a certain day is shown, wherein the power of the two-area AC-DC conversion device is positive, indicating that the flexible DC system absorbs power from the two areas; the power of the 1st and 3rd area AC-DC conversion device is negative, indicating that the flexible DC system provides power to the 1st and 3rd areas; the sum of the power of the 1st, 2nd and 3rd area PCS is approximately 0, indicating that the power of the two areas is transferred to the 1st and 3rd areas, proving that the on-site consumption of distributed photovoltaic power during the day is completed by the present application, and the occurrence of reverse overload of the distribution transformer caused by the return of distributed photovoltaic power is avoided.

[0177] ​In one embodiment, a computer device is provided, which may be a server, and its internal structure diagram may be as follows: Figure 7 As shown, the computer device includes a processor, memory, and a network interface connected via a system bus. The processor provides computing and control capabilities. The memory includes a non-volatile storage medium and internal memory. The non-volatile storage medium stores an operating system, computer programs, and a database. The internal memory provides an environment for the operation of the operating system and computer programs in the non-volatile storage medium. The database stores static and dynamic information data. The network interface communicates with external terminals via a network connection. When the computer program is executed by the processor, it implements the steps in the above method embodiments.

[0178] Those skilled in the art will understand that Figure 7 The structure shown is merely a block diagram of a portion of the structure related to the present invention and does not constitute a limitation on the computer device to which the present invention is applied. A specific computer device may include more or fewer components than those shown in the figure, or combine certain components, or have different component arrangements.

[0179] In addition, the present invention also provides a computer device, including a memory and a processor, wherein the memory stores a computer program, and the processor executes the computer program to implement the steps in the above method embodiments.

[0180] In addition, the present invention also provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps in the above method embodiments.

[0181] Those skilled in the art can understand that all or part of the processes in the above-mentioned embodiment methods can be completed by instructing relevant hardware through a computer program. The computer program can be stored in a non-volatile computer readable storage medium, and when executed, can include the processes of the above-mentioned embodiments. Any reference to memory, storage, database or other medium used in each embodiment of the present application can include at least one of non-volatile and volatile memory. Non-volatile memory can include read-only memory (ROM), magnetic tape, floppy disk, flash memory or optical memory, etc. Volatile memory can include random access memory (RAM) or external cache memory. As an illustration but not limitation, RAM can be in various forms, such as static random access memory (SRAM) or dynamic random access memory (DRAM), etc.

[0182] The present application is not limited to the structures described above and shown in the drawings, and various modifications and changes can be made without departing from the scope thereof. The scope of the present application is only limited by the appended claims.

Claims

1. A method for power supply mutual assistance of a transformer area, characterized in that, The power mutual assistance method of the transformer area comprises: According to the active power of the distribution transformer, the load rate of the distribution transformer is calculated in combination with the capacity of the distribution transformer, the load conditions of each transformer area are obtained, and the active power flow direction of the distribution transformer is set; Based on the load conditions of each transformer area, it is judged whether there is a heavy overload transformer area, and the total exceeding limit power of all forward heavy overload transformer areas and the total exceeding limit power of reverse heavy overload transformer areas are calculated, the exceeding limit power conditions of each transformer area are obtained, and a preliminary power distribution strategy is established; According to the preliminary power distribution strategy, the exceeding limit power of the heavy overload transformer area is distributed, and the remaining exceeding limit power is distributed to the adjacent transformer area based on the principle of proximity according to the electrical distance, until there is no heavy overload transformer area or the load rate of all transformer areas reaches the threshold condition; Based on the threshold condition that the load rate of all transformer areas reaches, the charge and discharge power of the direct current energy storage device is set, and the active power of the alternating current transformer area is adjusted through the charge and discharge operation of the direct current energy storage device.

2. The method of claim 1, wherein, The calculation of the load rate of the distribution transformer based on the active power of the distribution transformer in combination with the capacity of the distribution transformer, the load conditions of each transformer area are obtained, and the active power flow direction of the distribution transformer is set, which comprises: Based on all transformer areas, real-time data of distribution transformers are collected to obtain the active power of the distribution transformer; The load rate of the distribution transformer is calculated by using the active power of the distribution transformer in combination with the capacity of the distribution transformer; According to the load rate of the distribution transformer, the active power flow direction of the distribution transformer is set, and the power flow direction of each transformer area is determined.

3. The method for mutual power assistance between power distribution stations according to claim 2, characterized in that, The calculation expression of the load rate of the distribution transformer is: where λ i represents the load rate of distribution transformer of the station area i, P i represents the active power of distribution transformer of the station area i, S i represents the capacity of distribution transformer of the station area i; The active power of the distribution transformer flows from the medium voltage distribution network to the low voltage distribution network as forward.

4. The method for mutual power assistance between power distribution stations according to claim 3, characterized in that, The calculation expression of the total exceeding limit power of all forward heavy overload transformer areas is: In the formula, P Σ+ represents the sum of the over-limit power of all positive heavy overload substations, λ max represents the positive heavy load rate threshold of the substation; The calculation expression of the total exceeding limit power of all reverse heavy overload transformer areas is: In the formula, P Σ- represents the sum of the over-limit power of all reverse heavy overload substations, λ min represents the reverse heavy load rate threshold of the substation.

5. The method of claim 1, wherein, According to the preliminary power distribution strategy, the exceeding limit power of the heavy overload transformer area is distributed, and the remaining exceeding limit power is distributed to the adjacent transformer area based on the principle of proximity according to the electrical distance, until there is no heavy overload transformer area or the load rate of all transformer areas reaches the threshold condition, which comprises: Based on the preliminary power distribution strategy, the exceeding limit power of the heavy overload transformer area is distributed, and the remaining exceeding limit power is reserved; When there is no reverse heavy overload transformer area, the remaining exceeding limit power of the forward heavy overload transformer area is distributed to the adjacent transformer area according to the principle of proximity according to the electrical distance, until there is no forward heavy overload transformer area or the load rate of all transformer areas reaches the forward heavy overload load rate threshold; When there is no forward heavy overload transformer area, the remaining exceeding limit power of the reverse heavy overload transformer area is distributed to the adjacent transformer area according to the principle of proximity according to the electrical distance, until there is no reverse heavy overload transformer area or the load rate of all transformer areas reaches the reverse heavy overload load rate threshold.

6. The method of claim 5, wherein, The distribution of the exceeding limit power of the heavy overload transformer area based on the preliminary power distribution strategy and the reservation of the remaining exceeding limit power comprise: The total exceeding limit power of the forward heavy overload transformer area is compared with the total exceeding limit power of the reverse heavy overload transformer area; When the total over-limit power of the forward heavy overload substation area is greater than the total over-limit power of the reverse heavy overload substation area, the over-limit power of the forward over-limit substation area is preferentially allocated to the reverse over-limit substation area until there is no reverse heavy overload substation area, and the remaining over-limit power is reserved; When the total over-limit power of the forward heavy overload substation area is less than or equal to the total over-limit power of the reverse heavy overload substation area, the over-limit power of the reverse over-limit substation area is preferentially allocated to the forward over-limit substation area until there is no forward heavy overload substation area, and the remaining over-limit power is reserved.

7. The method of claim 1, wherein, The threshold condition that all substation load rates reach includes two cases: all substation load rates reach a forward heavy load rate threshold and all substation load rates reach a reverse heavy load rate threshold.

8. The method of claim 1, wherein, The threshold condition that all substation load rates reach includes two cases: all substation load rates reach a forward heavy load rate threshold and all substation load rates reach a reverse heavy load rate threshold. When all substation load rates reach the forward heavy load rate threshold, the total over-limit power of the forward heavy overload substation area is compared with the maximum discharge power of the DC energy storage device, and the discharge power of the DC energy storage device is determined based on the comparison result, and the active power of the AC substation area is supplied through the discharge operation of the DC energy storage device; When all substation load rates reach the reverse heavy load rate threshold, the total over-limit power of the reverse heavy overload substation area is compared with the maximum charge power of the DC energy storage device, and the charge power of the DC energy storage device is determined based on the comparison result, and the active power of the AC substation area is absorbed through the charge operation of the DC energy storage device.

9. A power mutual assistance system for transformer substations, characterized in that, The substation power mutual aid system includes an AC / DC conversion device, a DC interconnection line, a DC energy storage device, and a fusion terminal. The AC / DC conversion device is configured in each substation, and the AC side of the AC / DC conversion device is connected to the low-voltage bus of the corresponding substation. The DC interconnection line is used to connect the DC side of the AC / DC conversion device of each substation. The DC energy storage device is used to adjust the active power of the AC substation area through charge and discharge operations. The fusion terminal is used to collect the active power of the distribution transformer, analyze the load conditions and over-limit power conditions of each substation area, establish a preliminary power distribution strategy, and generate corresponding control instructions, and the corresponding control instructions are sent to the AC / DC conversion device. The fusion terminal includes a load rate analysis unit, an over-limit power judgment unit, a power distribution and optimization unit, and an energy storage regulation unit. The load rate analysis unit is used to calculate the load rate of the distribution transformer based on the active power of the distribution transformer and the capacity of the distribution transformer, and set the active power flow direction of the distribution transformer to obtain the load conditions of each substation area. The over-limit power judgment unit is used to determine whether there is a heavy overload substation area based on the load conditions of each substation area, calculate the total over-limit power of all forward heavy overload substation areas and the total over-limit power of reverse heavy overload substation areas, obtain the over-limit power conditions of each substation area, and establish a preliminary power distribution strategy. The over-limit power judgment unit is used to determine whether there is a heavy overload substation area based on the load conditions of each substation area, calculate the total over-limit power of all forward heavy overload substation areas and the total over-limit power of reverse heavy overload substation areas, obtain the over-limit power conditions of each substation area, and establish a preliminary power distribution strategy. The power distribution and optimization unit is configured to distribute the over-limit power of the heavily overloaded substation area according to a preliminary power distribution strategy, and distribute the remaining over-limit power to adjacent substation areas based on a principle of proximity according to electrical distance until there is no heavily overloaded substation area or all substation load rates reach a threshold condition. The energy storage adjustment unit is configured to set the charging and discharging power of the direct-current energy storage device based on the threshold condition that all substation load rates reach, and adjust the active power of the alternating-current substation through the charging and discharging operation of the direct-current energy storage device.

10. The power trading system of claim 9, wherein, The load rate analysis unit comprises an active power collection module, a load rate calculation module and a power flow direction module. The active power collection module is configured to collect real-time data of the distribution transformer based on all substation areas to obtain the active power of the distribution transformer. The load rate calculation module is configured to calculate the load rate of the distribution transformer by combining the active power of the distribution transformer with the capacity of the distribution transformer. The power flow direction module is configured to set the active power flow direction of the distribution transformer according to the load rate of the distribution transformer to determine the power flow direction of each substation area.

11. The power trading system of claim 10, wherein, The calculation expression of the load rate of the distribution transformer is as follows: In the formula, λ i represents the distribution transformer load rate of the transformer station i, P i represents the active power of the distribution transformer of the transformer station i, S i represents the distribution transformer capacity of the transformer station i; The active power flow direction of the distribution transformer is that the active power of the distribution transformer flows from the medium-voltage distribution network to the low-voltage distribution network in a positive direction.

12. The power trading system of claim 9, wherein, The power distribution and optimization unit comprises a preliminary power distribution module, a forward heavy overload optimization module and a reverse heavy overload optimization module. The preliminary power distribution module is configured to distribute the over-limit power of the heavily overloaded substation area based on a preliminary power distribution strategy, and reserve the remaining over-limit power. The forward heavy overload optimization module is configured to distribute the remaining over-limit power of the forward heavy overload substation area to adjacent substation areas according to the principle of proximity according to electrical distance until there is no forward heavy overload substation area or all substation load rates reach a forward heavy load rate threshold. The reverse heavy overload optimization module is configured to distribute the remaining over-limit power of the reverse heavy overload substation area to adjacent substation areas according to the principle of proximity according to electrical distance until there is no reverse heavy overload substation area or all substation load rates reach a reverse heavy load rate threshold.

13. The power trading system of claim 12, wherein, The preliminary power distribution module comprises an over-limit power comparison module, a forward preferential distribution module and a reverse preferential distribution module. The over-limit power comparison module is configured to compare the total over-limit power of the forward heavy overload substation area with the total over-limit power of the reverse heavy overload substation area. The forward preferential distribution module is configured to preferentially distribute the over-limit power of the forward over-limit substation area to the reverse over-limit substation area when the total over-limit power of the forward heavy overload substation area is greater than the total over-limit power of the reverse heavy overload substation area until there is no reverse heavy overload substation area, and reserve the remaining over-limit power. The reverse preferential distribution module is configured to preferentially distribute the over-limit power of the reverse over-limit substation area to the forward over-limit substation area when the total over-limit power of the forward heavy overload substation area is less than or equal to the total over-limit power of the reverse heavy overload substation area until there is no forward heavy overload substation area, and reserve the remaining over-limit power.

14. The power trading system of claim 9, wherein, The all-feeder load rate reaching the threshold condition includes two cases: all-feeder load rates reaching a positive overload load rate threshold and all-feeder load rates reaching a negative overload load rate threshold.

15. The power trading system of claim 9, wherein, The energy storage adjusting unit includes a positive overload control module and a negative overload control module. The positive overload control module is configured to, when all-feeder load rates reach the positive overload load rate threshold, compare the total overload power of the positive overload feeder with the maximum discharging power of the DC energy storage device, determine the discharging power of the DC energy storage device based on a comparison result, and supply the active power of the AC feeder through discharging operation of the DC energy storage device. The negative overload control module is configured to, when all-feeder load rates reach the negative overload load rate threshold, compare the total overload power of the negative overload feeder with the maximum charging power of the DC energy storage device, determine the charging power of the DC energy storage device based on a comparison result, and absorb the active power of the AC feeder through charging operation of the DC energy storage device.

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