A load balancing power supply system and method based on energy storage unit

Abstract

The present application proposes a load balancing power supply system and method for a substation based on an energy storage unit. The power supply system is used to regulate the three-phase load in a distribution substation in real time by setting an independent energy storage unit, a shared energy storage unit, a switch network and a substation terminal. When the distribution terminal calculates that a phase in the substation is overloaded, the charging and discharging power of the independent energy storage unit is first adjusted by controlling the operating state of the independent energy storage unit connected to the phase line, thereby changing the load level of the phase line. When the load balancing adjustment demand exceeds the maximum adjustable range of the independent energy storage unit, it is necessary to work with the shared energy storage unit for further coordination. The load balancing power supply method broadens the depth of managing the unbalanced load in the substation through the coordinated regulation of the independent energy storage unit and the shared energy storage unit, and can effectively respond to the occurrence of extreme load on a phase in the substation in real time, thereby improving the power supply reliability.

Description

Technical Field

[0001] The present invention relates to the field of intelligent power distribution and energy storage technology, and in particular to a load balancing power supply system and method for an energy storage unit. Background Art

[0002] In the power distribution system, three-phase load imbalance is a common and serious problem, especially in the low-voltage distribution network. Three-phase load imbalance can lead to many negative effects, such as voltage imbalance, shortened equipment life, reduced energy efficiency, and electromagnetic interference. Among them, voltage imbalance is due to the uneven distribution of load among the three phases, which will cause different voltages in each phase, affecting power quality and equipment operation; equipment life is shortened, unbalanced load will increase additional losses in transformers, neutral lines and other distribution equipment, shortening their service life; energy efficiency is reduced, three-phase imbalance leads to reduced system efficiency, increased power loss and operating costs; electromagnetic interference, unbalanced load will generate electromagnetic interference, affecting the normal operation of other equipment.

[0003] With the development of the distribution system, the factors that lead to unbalanced three-phase load are also increasing. Taking the transformer in the substation as an example, the form of its access load is becoming more and more complex and changeable, which will aggravate the unbalanced load in the distribution substation. The randomness of load distribution, the load in the distribution network is usually random and uncertain. The load types and power consumption times in residential areas, commercial areas and industrial areas are different, resulting in uneven load distribution. For example, the load in residential areas is higher at night, while the load in commercial areas is higher during the day; single-phase load access, many loads are single-phase access, such as household appliances, lighting equipment, etc. The randomness of single-phase load access increases the possibility of unbalanced three-phase load. The access of electric vehicles and renewable energy, with the popularization of electric vehicles and distributed renewable energy (such as solar energy and wind energy), their unstable power output characteristics increase the unbalanced load of the distribution system.

[0004] The main methods for managing the unbalanced load in the distribution network in the existing technology include dynamic load regulation, optimization of the distribution network structure, intelligent monitoring and management system, etc. Among them, dynamic load regulation can adjust the load of each phase in real time and balance the three-phase load by installing dynamic adjustment equipment (such as phase-adjusting transformers, automatic adjustment devices, etc.); optimizing the distribution network structure can reasonably distribute the load by optimizing the structure and topology of the distribution network and reduce the impact of the unbalanced three-phase load; the intelligent monitoring and management system can use advanced monitoring and management systems to monitor the load of the distribution network in real time, and take measures to balance the load in advance through data analysis and prediction. However, the above methods for managing the unbalanced load in the distribution network have limitations. For example, dynamic load regulation requires the load to be phase-changed or the load to be started and stopped for a short time, which greatly affects the power supply quality of the distribution network and damages the interests of power users; and the regulation depth and balancing capacity are limited. In the case of extreme load access or exit, the dynamic balance of the three-phase load cannot be achieved; in addition, the response speed is slow, and it is impossible to achieve real-time dynamic and effective response to various load imbalances.

[0005] Therefore, based on the requirements of the development of the existing distribution network, the present invention combines the development trend of energy storage technology and proposes a substation load balancing power supply system and method based on energy storage units to solve the technical problem of unbalanced three-phase load in the distribution network system, thereby improving the power supply quality of the distribution network, enhancing the power supply reliability, and being able to effectively solve various load imbalance situations. Summary of the invention

[0006] In order to solve the above technical problems, the present application proposes a load balancing power supply system and method based on energy storage units, which are as follows:

[0007] A load balancing power supply system based on energy storage units, including a 10kV incoming line, an area transformer, an energy storage unit, an area terminal and a cloud platform. The 10kV incoming line is transformed by the area transformer to supply power to the low-voltage load. The energy storage unit includes an independent energy storage unit and a shared energy storage unit. The independent energy storage units are divided into three groups, A, B, and C, which are respectively connected to the three-phase busbars A, B, and C on the low-voltage side of the area transformer. Each independent energy storage unit includes m battery groups and inverter units. The m battery groups are connected to the AC busbars of the corresponding phase lines via corresponding inverters. The shared energy storage unit includes a switch network, n battery packs and n inverters corresponding to the battery packs one by one. The switch network includes n energy storage connection terminals, 3 phase line connection terminals and 3n controllable switches. The n battery packs of the shared energy storage unit are respectively connected to the energy storage connection terminals of the switch network via corresponding inverters. The phase line connection terminals of the switch network are respectively connected to the three-phase busbars A, B, and C on the low-voltage side of the substation transformer. Inside the switch network, each energy storage connection terminal of the switch network is connected to each phase line connection terminal of the switch network via 3 controllable switches.

[0008] The substation terminal is used to collect the load data of each phase line, the operating data of each battery pack and inverter in the substation, analyze the substation operation status based on the collected data, and then issue control instructions to the inverter and switch network of each energy storage unit based on the analysis results.

[0009] The control instructions include controlling the on and off of the switch and adjusting the charging or discharging power of the inverter; instructions and data interaction can be generated between the substation terminal and the cloud platform.

[0010] Furthermore, based on the above-mentioned load balancing power supply system for the substation, a method for substation load balancing based on an energy storage unit is proposed, comprising the following steps:

[0011] Step 1: Collect the operation information of the substation, including the current of each phase, the operation status of the energy storage unit, and the operation status of the switch network;

[0012] Step 2: Calculate the unbalance degree d of the substation according to the collected current values ​​of each phase;

[0013] Step 3: Determine whether the balance exceeds the operating threshold. If it exceeds the operating threshold, further sort the phase line loads according to the three-phase current size to obtain the load reduction phase, the load phase and the load reduction power P that meets the operating threshold. - and loading power P + ;

[0014] Step 4: Calculate the maximum adjustable charging power value P of each group of independent energy storage units A, B, and C based on the collected independent energy storage unit operating status information charge and the maximum adjustable discharge power value P discharge ; Calculate the maximum adjustable charging power value and the maximum adjustable discharging power value of the shared energy storage unit according to the collected operating status of the shared energy storage unit and the operating status information of the switch network;

[0015] Step 5: Determine the load shedding power value P of the load shedding phase - Is it less than the maximum adjustable discharge power value P of the independent energy storage unit in the load reduction phase? discharge If it is less than, then the load reduction power value P - Control the independent energy storage unit in the load reduction phase to discharge; otherwise, discharge is performed jointly through the shared energy storage unit;

[0016] Step 6: Determine the loading power value P of the loading phase + Is it less than the maximum adjustable charging power value P of the independent energy storage unit under this loading phase? charge If it is less than, then the load power value P + The independent energy storage units under the loading phase are controlled to be charged; otherwise, they are jointly charged through the shared energy storage units.

[0017] Furthermore, the step 5 further comprises:

[0018] Step 5-1: When the shared energy storage unit is required to discharge jointly, the load reduction power P of the load reduction phase is - and the maximum adjustable discharge power value P of the independent energy storage unit in the load reduction phase discharge Calculate the discharge power value P of the shared energy storage unit share- , the calculation formula is: P share- =P - -k1P discharge , where k1 is the discharge coefficient, which indicates the margin of the discharge output of the independent energy storage unit, satisfying 0 <k1<1;

[0019] Step 5-2: Based on the calculated discharge power value P of the shared energy storage unit share- and the switch network status, determine the switch that needs to be controlled to be turned on, and send a switch turn-on instruction to the switch network through the substation terminal to realize the discharge switching of the shared energy storage unit of the load-shedding phase.

[0020] Furthermore, step 6 also includes:

[0021] Step 6-1: When a shared energy storage unit is required to be charged jointly, the loading power P of the load reduction phase is + and the maximum adjustable charging power value P of the independent energy storage unit under this loading phase charge Calculate the charging power value P of the shared electric energy storage unit share+ , the calculation formula is: P share+ =P + -k2P charge , where k2 is the charging coefficient, which indicates the margin of the charging output of the independent energy storage unit, satisfying 0 <k2<1;

[0022] Step 6-2: Based on the calculated charging power value P of the shared electric energy storage unit share+ and the switch network status, determine the switch that needs to be controlled to be turned on, and send a switch turn-on instruction to the switch network through the substation terminal to realize the charging and switching of the loaded phase shared energy storage unit.

[0023] Furthermore, after step 6, the following steps are further included:

[0024] Step 7: The substation terminal dynamically calculates the substation imbalance d. When the fluctuation value △d of the imbalance d exceeds the threshold or the fluctuation value △P of any phase line load exceeds the threshold, repeat the above steps and recalculate the switching capacity of the independent energy storage unit and the shared energy storage unit.

[0025] Furthermore, after step 7, the following steps are further included:

[0026] Step 8: As the energy storage units are charged and discharged, the charging and discharging output of each energy storage unit will also change. When the substation terminal monitors the maximum adjustable charging power value P of each group of independent energy storage units A, B, and C, charge , Maximum adjustable discharge power value P discharge , the discharge power value P of the shared energy storage unit share- , the charging power value P of the shared electric energy storage unit share+ When the value changes and fails to meet the threshold requirement, the above calculation steps are repeated to recalculate the maximum adjustable charging power value P of each group of independent energy storage units A, B, and C. charge , Maximum adjustable discharge power value P discharge , the discharge power value P of the shared energy storage unit share- , the charging power value P of the shared electric energy storage unit share+ , and dynamically adjust the switching capacity of independent energy storage units and shared energy storage units accordingly;

[0027] Further, the calculation formula of the imbalance degree is:

[0028] ; ;in, is the three-phase current, is the average value of the three-phase current.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] 1) A load balancing method based on energy storage units is proposed. Independent energy storage units and shared energy storage units are set on the three-phase bus on the low-voltage side of the distribution station area. The charging and discharging operation modes of the independent energy storage units and the shared energy storage units are controlled in real time by the distribution terminal to solve the problem of unbalanced three-phase load in the distribution station area.

[0031] 2) The energy storage unit-based load balancing method described in this application, through the coordinated regulation of independent energy storage units and shared energy storage units, broadens the depth of managing load imbalance in the substation, can effectively respond to the occurrence of extreme load on a certain phase in the substation in real time, and improves power supply reliability.

[0032] 3) A distribution network structure based on independent energy storage units and shared energy storage units is proposed. By setting up independent energy storage units, shared energy storage units, switch networks and substation terminals, it is used to control the three-phase load in the distribution substation in real time, thereby solving the problem of unbalanced three-phase load. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present application. For those skilled in the art, other drawings can be obtained based on the provided drawings without paying any creative work.

[0034] Figure 1 This is a diagram of the power supply structure of the substation in an embodiment of the present invention.

[0035] Figure 2 Schematic diagram of the structure of an independent energy storage unit in an embodiment of the present invention.

[0036] Figure 3 Schematic diagram of the shared energy storage unit in an embodiment of the present invention.

[0037] Figure 4 This is a diagram of a power supply structure for an area based on independent energy storage units and shared energy storage units in an embodiment of the present invention.

[0038] Figure 5 Schematic diagram of a substation terminal control switch network in an embodiment of the present invention.

[0039] Figure 6 It is a schematic diagram of a substation terminal controlling an inverter in an embodiment of the present invention. DETAILED DESCRIPTION

[0040] In order to make the purpose, technical scheme and advantages of the implementation of the present invention clearer, the technical scheme in the embodiment of the present invention will be described in more detail below in conjunction with the drawings in the embodiment of the present invention. In the drawings, the same or similar reference numerals throughout represent the same or similar elements or elements with the same or similar functions. The described embodiments are part of the embodiments of the present invention, not all of the embodiments. The embodiments described below with reference to the drawings are exemplary and are intended to be used to explain the present invention, and should not be construed as limitations on the present invention. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0041] For the management of load imbalance in distribution networks, dynamic load regulation in the prior art can adjust the load of each phase in real time and balance the three-phase load by installing dynamic regulation equipment; optimize the distribution network structure by optimizing the structure and topology of the distribution network, reasonably distribute the load, and reduce the impact of three-phase load imbalance; the intelligent monitoring and management system uses advanced monitoring and management systems to monitor the load conditions of the distribution network in real time, and take measures to balance the load in advance through data analysis and prediction. However, the above methods for managing load imbalance in distribution networks have limitations. For example, dynamic load regulation requires phase switching or short-term load start and stop, which greatly affects the power supply quality of the distribution network and damages the interests of power users; and the regulation depth and balancing ability are limited. In the case of extreme load access or exit, the dynamic balance of the three-phase load cannot be achieved; in addition, the response speed is slow, and it is impossible to achieve real-time dynamic and effective response to various load imbalance situations.

[0042] In response to the above technical problems, the present application proposes a load balancing power supply system and method based on an energy storage unit. In order to enable technical personnel in this field to better understand the present solution, the present application is further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0043] Embodiment 1

[0044] As attached Figure 1 , 4 -6 shows the power supply structure diagram and control schematic diagram of the substation, the power supply system shown includes a 10kV incoming line, a substation transformer, an energy storage unit, a substation terminal and a cloud platform. The 10kV incoming line is transformed by the substation transformer to supply power to the low-voltage load. The energy storage unit includes an independent energy storage unit and a shared energy storage unit. The independent energy storage unit is divided into three groups, A, B, and C, which correspond to the three-phase busbars A, B, and C on the low-voltage side of the substation transformer respectively; the shared energy storage unit includes a switch network, n battery packs, and n inverters corresponding to the battery packs one by one; the substation terminal is used to collect the load data of each phase line under the substation, the operating data of each battery pack and the inverter, analyze the substation operation status according to the collected data, and then issue control instructions to the inverter and switch network of each energy storage unit according to the analysis results. The control instructions include controlling the on and off of the switch and adjusting the charging or discharging power of the inverter; instructions and data interaction can be generated between the substation terminal and the cloud platform.

[0045] Embodiment 2

[0046] As attached Figure 2-3The independent energy storage unit and shared energy storage unit shown in the figure, each independent energy storage unit includes m battery groups and inverter units, the m battery groups are connected to the AC bus of the corresponding phase line through the corresponding inverter; the shared energy storage unit includes a switch network, n battery groups and n inverters corresponding to the battery groups one by one, the switch network includes n energy storage connection terminals and 3 phase line connection terminals and 3n controllable switches, the n battery groups of the shared energy storage unit are respectively connected to the energy storage connection terminals of the switch network through the corresponding inverters, the phase line connection terminals of the switch network are respectively connected to the three-phase bus A, B, and C on the low-voltage side of the substation transformer, and inside the switch network, the energy storage connection terminals of the switch network are respectively connected to the phase line connection terminals of the switch network through 3 controllable switches; based on such a connection relationship, the battery groups of each shared energy storage unit can be selectively connected to the phase bus of the transformer under the control of the substation terminal, thereby realizing load adjustability.

[0047] Specifically, as attached Figure 2 As shown, for independent energy storage units, corresponding to the three-phase voltage bus A, B, and C, the independent energy storage units are divided into three groups A, B, and C, which correspond to the three-phase bus A, B, and C connected to the low-voltage side of the substation transformer respectively. Each independent energy storage unit includes m battery packs and inverter units, and the m battery packs are connected to the AC bus of the corresponding phase line through the corresponding inverter; wherein the independent energy storage unit group A includes battery packs A1-Ai, the independent energy storage unit group B includes battery packs B1-Bi, and the independent energy storage unit group C includes battery packs C1-Ci, and i is an integer greater than 0 and less than or equal to m; the substation terminal can control the charging and discharging power of the inverter of the independent energy storage unit, thereby controlling the charging and discharging state of each battery pack; the inverter adopts a bidirectional inverter, and realizes the charging or discharging of the battery pack through PWM control.

[0048] Specifically, as attached Figure 3 As shown, for a shared energy storage unit, it includes a switch network, n battery groups and n inverters corresponding to the battery groups one by one, the switch network includes n energy storage connection terminals, 3 phase line connection terminals and 3n controllable switches, the n battery groups of the shared energy storage unit are respectively connected to the energy storage connection terminals of the switch network via corresponding inverters, the phase line connection terminals of the switch network are respectively connected to the three-phase busbars A, B, and C on the low-voltage side of the substation transformer, and inside the switch network, each energy storage connection terminal of the switch network is connected to each phase line connection terminal of the switch network via 3 controllable switches; based on this connection relationship, under the control of the substation terminal, each battery group under the shared energy storage unit can choose to be connected to any of the three phases A, B, and C for charging or discharging, and when the battery group is full, it can also achieve off-grid operation by controlling the switch; the switch is a circuit breaker configured according to the capacity of the energy storage unit.

[0049] Embodiment 3

[0050] As attached Figure 4-6 As shown in the schematic diagram of the power supply structure and control of the substation, when the distribution terminal calculates that a phase in the substation is overloaded, the charging and discharging power of the independent energy storage unit is first adjusted by controlling the operating status of the independent energy storage unit connected to the phase line, thereby changing the load level of the phase line; specifically, after obtaining the charge status of all battery packs in the independent energy storage unit, the rechargeable and dischargeable battery packs are identified, and then control instructions are issued to the inverter connected to the battery pack through the substation terminal, including: instructions for adjusting the charging and discharging power size, instructions for switching the charging and discharging status, thereby adjusting the load level of the phase line.

[0051] When the load balancing adjustment demand exceeds the maximum adjustable range of the independent energy storage unit, it is necessary to work together with the shared energy storage unit for further coordination. Specifically, first identify the switch network status of the current shared energy storage unit, that is, the connection status of the battery group under the shared energy storage unit and the three-phase voltage bus, and further identify the battery group in the charging state and the battery group in the discharging state. According to the load amount that needs to be adjusted, control instructions are preferentially sent to the inverter connected to the battery group through the substation terminal, including: instructions for adjusting the charging and discharging power, instructions for switching the charging and discharging states, so as to adjust the load level of the phase line under the existing switch network state. If the load balancing threshold requirement cannot be met, further switch the connection relationship between the battery group under the shared energy storage unit and the three-phase bus by controlling the on and off of the switch network, so as to adjust the load level of each phase line and achieve phase line load balancing.

[0052] Embodiment 4

[0053] Based on the power supply structure and energy storage unit of the above embodiment, the specific steps of performing load balancing in the area are as follows:

[0054] Step 1: Collect the operation information of the substation, including the current of each phase, the operation status of the energy storage unit, and the operation status of the switch network;

[0055] Step 2: Calculate the unbalance degree d of the substation according to the collected current values ​​of each phase;

[0056] Step 3: Determine whether the balance exceeds the operating threshold. If it exceeds the operating threshold, further sort the phase line loads according to the three-phase current size to obtain the load reduction phase, the load phase and the load reduction power P that meets the operating threshold. - and loading power P + ;

[0057] Step 4: Calculate the maximum adjustable charging power value P of each group of independent energy storage units A, B, and C based on the collected independent energy storage unit operating status information charge and the maximum adjustable discharge power value P discharge; Calculate the maximum adjustable charging power value and the maximum adjustable discharging power value of the shared energy storage unit according to the collected operating status of the shared energy storage unit and the operating status information of the switch network;

[0058] Step 5: Determine the load shedding power value P of the load shedding phase - Is it less than the maximum adjustable discharge power value P of the independent energy storage unit in the load reduction phase? discharge If it is less than, then the load reduction power value P - Control the independent energy storage unit in the load reduction phase to discharge; otherwise, discharge is performed jointly through the shared energy storage unit;

[0059] Step 6: Determine the loading power value P of the loading phase + Is it less than the maximum adjustable charging power value P of the independent energy storage unit under this loading phase? charge If it is less than, then the load power value P + The independent energy storage units under the loading phase are controlled to be charged; otherwise, they are jointly charged through the shared energy storage units.

[0060] Embodiment 5

[0061] Based on the load balancing method for the substation area described in the fourth embodiment, under the working condition that the shared energy storage units need to be jointly discharged, the load balancing method for the substation area further includes the following steps:

[0062] Step 5-1: When the shared energy storage unit is required to discharge jointly, the load reduction power P of the load reduction phase is - and the maximum adjustable discharge power value P of the independent energy storage unit in the load reduction phase discharge Calculate the discharge power value P of the shared energy storage unit share- , the calculation formula is: P share- =P - -k1P discharge , where k1 is the discharge coefficient, which indicates the margin of the discharge output of the independent energy storage unit, satisfying 0 <k1<1;

[0063] Step 5-2: Based on the calculated discharge power value P of the shared energy storage unit share- and the switch network status, determine the switch that needs to be controlled to be turned on, and send a switch turn-on instruction to the switch network through the substation terminal to realize the discharge switching of the shared energy storage unit of the load-shedding phase.

[0064] Embodiment 6

[0065] Based on the load balancing method for the substation area described in the fourth embodiment, under the condition that the shared energy storage unit needs to be charged jointly, the load balancing method for the substation area further includes the following steps:

[0066] Step 6-1: When a shared energy storage unit is required to be charged jointly, the loading power P of the load reduction phase is + and the maximum adjustable charging power value P of the independent energy storage unit under this loading phase charge Calculate the charging power value P of the shared electric energy storage unit share+ , the calculation formula is: P share+ =P + -k2P charge , where k2 is the charging coefficient, which indicates the margin of the charging output of the independent energy storage unit, satisfying 0 <k2<1;

[0067] Step 6-2: Based on the calculated charging power value P of the shared electric energy storage unit share+ and the switch network status, determine the switch that needs to be controlled to be turned on, and send a switch turn-on instruction to the switch network through the substation terminal to realize the charging and switching of the loaded phase shared energy storage unit.

[0068] Embodiment 7

[0069] Based on the load balancing method for the substation area described in the above embodiment, after steps 1-6, it is necessary to dynamically monitor the load balance and dynamically adjust the operating status of the independent energy storage unit and the shared energy storage unit. The load balancing method for the substation area further includes the following steps:

[0070] Step 7: The substation terminal dynamically calculates the unbalance degree d of the substation. When the fluctuation value △d of the unbalance degree d exceeds the threshold or the fluctuation value △P of any phase line load exceeds the threshold, the above steps 1-6 are repeated to recalculate the switching amount of the independent energy storage unit and the shared energy storage unit;

[0071] Step 8: As the energy storage units are charged and discharged, the charging and discharging output of each energy storage unit will also change. When the substation terminal monitors the maximum adjustable charging power value P of each group of independent energy storage units A, B, and C, charge , Maximum adjustable discharge power value P discharge , the discharge power value P of the shared energy storage unit share- , the charging power value P of the shared electric energy storage unit share+ When the value changes and fails to meet the threshold requirement, the above calculation steps are repeated to recalculate the maximum adjustable charging power value P of each group of independent energy storage units A, B, and C. charge , Maximum adjustable discharge power value P discharge , the discharge power value P of the shared energy storage unit share- , the charging power value P of the shared electric energy storage unit share+ , and dynamically adjust the switching capacity of independent energy storage units and shared energy storage units accordingly.

[0072] The calculation formula of the imbalance degree is:

[0073] ; ;in, is the three-phase current, is the average value of the three-phase current.

[0074] Those skilled in the art should understand that although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible to modify the technical solutions described in the aforementioned embodiments, or to make equivalent replacements for some or all of the technical features therein; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention. The above embodiments are only used to illustrate the technical solutions of the present invention, not to limit them.

Claims

1. A load balancing method for a substation based on an energy storage unit, wherein the load balancing method is implemented by a load balancing power supply system for a substation based on an energy storage unit, and is characterized in that: The substation load balancing power supply system includes a 10kV incoming line, a substation transformer, an energy storage unit, a substation terminal and a cloud platform. The 10kV incoming line is transformed by the substation transformer to supply power to the low-voltage load. The energy storage unit includes an independent energy storage unit and a shared energy storage unit. The independent energy storage units are divided into three groups, A, B, and C, which are respectively connected to the three-phase busbars A, B, and C on the low-voltage side of the substation transformer. Each independent energy storage unit includes m battery packs and inverter units. The m battery packs are connected to the AC busbars of the corresponding phase lines via corresponding inverters; the shared The shared energy storage unit includes a switch network, n battery packs, and n inverters corresponding to the battery packs. The switch network includes n energy storage connection terminals, 3 phase line connection terminals, and 3n controllable switches. The n battery packs of the shared energy storage unit are connected to the energy storage connection terminals of the switch network through the corresponding inverters. The phase line connection terminals of the switch network are respectively connected to the three-phase busbars A, B, and C on the low-voltage side of the transformer in the station area. Inside the switch network, each energy storage connection terminal of the switch network is connected to each phase line connection terminal of the switch network through 3 controllable switches. The load balancing method comprises the following steps: Step 1: Collect the operation information of the substation, including the current of each phase, the operation status of the energy storage unit, and the operation status of the switch network; Step 2: Calculate the unbalance degree d of the substation according to the collected current values ​​of each phase; the calculation formula of the unbalance degree is: ； ； in, , , is the three-phase current, is the average value of the three-phase current; Step 3: Determine whether the balance exceeds the operating threshold. If it exceeds the operating threshold, further sort the phase line loads according to the three-phase current size to obtain the load reduction phase, the load phase and the load reduction power P that meets the operating threshold. - and loading power P + ; Step 4: Calculate the maximum adjustable charging power value P of each group of independent energy storage units A, B, and C based on the collected independent energy storage unit operating status information charge and the maximum adjustable discharge power value P discharge ; Calculate the maximum adjustable charging power value and the maximum adjustable discharging power value of the shared energy storage unit according to the collected operating status of the shared energy storage unit and the operating status information of the switch network; Step 5: Determine the load shedding power value P of the load shedding phase - Is it less than the maximum adjustable discharge power value P of the independent energy storage unit in the load reduction phase? discharge If it is less than, then the load reduction power value P - Control the independent energy storage unit in the load reduction phase to discharge; otherwise, discharge is performed jointly through the shared energy storage unit; The step 5 also includes: Step 5-1: When the shared energy storage unit is required to discharge jointly, the load reduction power P of the load reduction phase is - and the maximum adjustable discharge power value P of the independent energy storage unit in the load reduction phase discharge Calculate the discharge power value P of the shared energy storage unit share- , the calculation formula is: P share- =P - -k1P discharge , where k1 is the discharge coefficient, which indicates the margin of the discharge output of the independent energy storage unit, satisfying 0 <k1<1; Step 5-2: Based on the calculated discharge power value P of the shared energy storage unit share- and the switch network status, determine the switch that needs to be controlled to be turned on, and send a switch turn-on instruction to the switch network through the substation terminal to realize the discharge switching of the shared energy storage unit in the load-shedding phase; Step 6: Determine the loading power value P of the loading phase + Is it less than the maximum adjustable charging power value P of the independent energy storage unit under this loading phase? charge If it is less than, then the load power value P + Control the independent energy storage unit in the loading phase to charge; otherwise, charge jointly through the shared energy storage unit; The step 6 also includes: Step 6-1: When a shared energy storage unit is required to be charged jointly, the loading power P of the load reduction phase is + and the maximum adjustable charging power value P of the independent energy storage unit under this loading phase charge Calculate the charging power value P of the shared electric energy storage unit share+ , the calculation formula is: P share+ =P + -k2P charge , where k2 is the charging coefficient, which indicates the margin of the charging output of the independent energy storage unit, satisfying 0 <k2<1; Step 6-2: Based on the calculated charging power value P of the shared electric energy storage unit share+ and the switch network status, determine the switch that needs to be controlled to be turned on, and send a switch-on instruction to the switch network through the substation terminal to realize the charging and switching of the shared energy storage unit of the loading phase; Step 7: The substation terminal dynamically calculates the unbalance degree d of the substation. When the fluctuation value △d of the unbalance degree d exceeds the threshold or the fluctuation value △P of any phase line load exceeds the threshold, the above steps are repeated to recalculate the switching amount of the independent energy storage unit and the shared energy storage unit; Step 8: As the energy storage units are charged and discharged, the charging and discharging output of each energy storage unit will also change. When the substation terminal monitors the maximum adjustable charging power value P of each group of independent energy storage units A, B, and C, charge , Maximum adjustable discharge power value P discharge , the discharge power value P of the shared energy storage unit share- , the charging power value P of the shared electric energy storage unit share+ When the value changes and fails to meet the threshold requirement, the above calculation steps are repeated to recalculate the maximum adjustable charging power value P of each group of independent energy storage units A, B, and C. charge , Maximum adjustable discharge power value P discharge , the discharge power value P of the shared energy storage unit share- , the charging power value P of the shared electric energy storage unit share+ , and dynamically adjust the switching capacity of independent energy storage units and shared energy storage units accordingly.

2. The method for balancing load in a substation area according to claim 1, characterized in that: The substation terminal is used to collect the load data of each phase line, the operating data of each battery pack and inverter in the substation, analyze the substation operation status based on the collected data, and then issue control instructions to the inverter and switch network of each energy storage unit based on the analysis results.

3. The load balancing method according to claim 2, characterized in that: The control instructions include controlling the on and off of the switch and adjusting the charging or discharging power of the inverter; instructions and data interaction can be generated between the substation terminal and the cloud platform.

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