A transformer voltage regulation method and system based on reactive power and phase balance

Abstract

The application discloses a kind of reactive power and phase balance-based area voltage management method and system, belong to distribution network low-voltage area operation control and power quality management technical field, the method is: based on area topological connection relationship, branch parameter and current operation quantity measurement constructs voltage approximation model, obtains load side three-phase unbalance index and several heavy load phase charging piles;Voltage side three-phase unbalance index is obtained;Based on load side three-phase unbalance index, voltage side three-phase unbalance index and preset weight coefficient constructs joint optimization objective function;Based on voltage approximation model and preset constraint condition constructs target constraint condition;Based on several heavy load phase charging piles, obtain candidate phase scheme set, based on target constraint condition, candidate phase scheme set and joint optimization objective function, obtain phase scheduling result and target reactive power adjustment amount, output charging pile executable instruction, on the premise that existing distribution equipment configuration is not changed, realize area voltage qualified management and three-phase load balance optimization.

Description

Technical Field

[0001] This invention relates to the field of low-voltage distribution area operation control and power quality management technology, and particularly to a distribution area voltage management method and system based on reactive power and phase balance. Background Technology

[0002] In modern power systems, low-voltage distribution substations generally adopt a three-phase four-wire power supply architecture. These substations have relatively high line resistance and reactance, with voltage loss primarily consisting of resistive voltage drop. The voltage at the terminal nodes is easily affected by load fluctuations. Furthermore, the load distribution of users within these substations is dispersed, and their electricity consumption behavior exhibits significant randomness and time-varying characteristics. In recent years, with the rapid development of the electric vehicle industry and the large-scale deployment of charging infrastructure in residential communities, industrial parks, and public parking lots, the proportion of charging load within low-voltage distribution substations has been continuously increasing. This charging load exhibits significant concentration and time-dependent characteristics. During peak electricity consumption periods such as evening rush hours, a large number of electric vehicles simultaneously connect to the charging circuit, leading to a sharp increase in the total current within the substation and a significant increase in line resistive voltage drop. This can easily cause the voltage at the terminal nodes of the substation to drop below the lower limit allowed by national standards, triggering voltage exceedance issues. Meanwhile, the AC slow-charging piles widely used in low-voltage distribution areas mostly adopt single-phase access. The charging access behavior of electric vehicle users is highly random, easily leading to severe imbalances in the three-phase load distribution. This, in turn, causes a series of power quality problems such as excessive three-phase voltage imbalance, excessive neutral current, increased losses in distribution transformers and lines, and abnormal equipment temperature rise. In areas with dense charging stations, frequent voltage fluctuations at local nodes may also occur, seriously affecting the user charging experience and the safe and stable operation of electrical equipment.

[0003] Traditional methods for addressing voltage and three-phase imbalance in low-voltage distribution areas primarily rely on engineering approaches such as upgrading distribution transformers, installing centralized reactive power compensation devices (e.g., parallel capacitor banks, static var generators (SVG), and static var compensators (SVCs), replacing conductors with larger cross-section ones, or optimizing the distribution network topology. However, these methods generally suffer from high construction investment, long implementation periods, and high operation and maintenance costs. Furthermore, they are difficult to adapt quickly to the highly random and volatile characteristics of charging loads, resulting in limited effectiveness.

[0004] On the other hand, existing electric vehicle charging piles generally adopt fully controlled power electronic converter interfaces, which have rapid current regulation capabilities and can provide a certain range of reactive power regulation capabilities while ensuring the active power demand of users. Some charging stations have already configured charging terminals in a balanced manner on the three-phase lines during the construction phase, or use single-phase charging piles with phase switching function or three-phase power adjustable charging piles, giving them the potential for physical three-phase load balancing regulation. However, in current engineering applications, charging piles are usually regarded as uncontrollable pure electrical loads. Even if some charging piles have power factor regulation functions, they mostly adopt single-pile independent control or static parameter setting mode, lacking a group control coordination mechanism oriented towards the overall optimization goal of the transformer area.

[0005] In summary, traditional governance methods in the existing technology involve large investments, long implementation cycles, and are difficult to adapt to the highly random nature of charging loads. They are also unable to achieve simultaneous optimization of qualified voltage and three-phase load balance in the distribution area without affecting users' normal charging needs or changing the configuration of existing power distribution equipment. Furthermore, they cannot effectively take into account the communication conditions of the edge terminals in the distribution area, the action constraints of the charging pile equipment, and the operational stability of the control system. Summary of the Invention

[0006] This invention provides a method and system for managing transformer voltage based on reactive power and phase balance. It can solve the technical problems of traditional management methods in the prior art, such as large investment, long implementation cycle, difficulty in adapting to the strong randomness of charging load, and the inability of single-objective management to take into account voltage quality and three-phase balance. It can simultaneously achieve qualified management of transformer voltage and optimization of three-phase load balance without changing the configuration of existing power distribution equipment.

[0007] This invention provides a method for managing transformer substation voltage based on reactive power and phase balance, comprising: A voltage approximation model is constructed based on the pre-acquired transformer area topology, branch parameters, and current operating measurements. Based on the topological connection relationship of the transformer area and the current operation measurement, the load-side three-phase imbalance index and several heavily loaded phase charging piles are obtained. Obtain several three-phase voltage phasors corresponding to several key nodes in the transformer area, and obtain the three-phase unbalance index on the voltage side based on the several three-phase voltage phasors; Three-phase imbalance evaluation index is obtained based on the load-side three-phase imbalance index and the voltage-side three-phase imbalance index; A joint optimization objective function is constructed based on the three-phase imbalance evaluation index and the preset weight coefficients; Target constraints are constructed based on the voltage approximation model and preset constraints. Based on several heavy-load phase charging piles, a candidate phase-specific scheme set is obtained, and based on the target constraints, the candidate phase-specific scheme set, and the joint optimization objective function, the phase-specific scheduling result and the target reactive power adjustment amount are obtained; Based on the phase scheduling results and the target reactive power adjustment, the output can execute instructions for the charging pile.

[0008] The above-mentioned scheme constructs a voltage approximation model, simultaneously acquires three-phase imbalance indices on the load side and voltage side, and forms a comprehensive evaluation index. Based on this, a joint optimization objective function and objective constraints are constructed. A candidate phase-specific scheme set is generated based on the heavily loaded phase charging piles, and the phase-specific scheduling results and target reactive power adjustment are solved. Finally, executable commands for the charging piles are output. Without changing the existing power distribution equipment configuration, this scheme simultaneously achieves voltage compliance management and three-phase load balance optimization in the distribution area, fully utilizing the adjustment capabilities of existing charging piles to replace some dedicated management resources. This solves the technical problems of traditional management methods, such as high investment, long implementation cycles, difficulty in adapting to the strong randomness of electricity loads, and the inability of single-objective management to simultaneously address voltage quality and three-phase balance.

[0009] Furthermore, the construction of the voltage approximation model based on the pre-acquired transformer area topology connections, branch parameters, and current operating measurements includes: Obtain the topology connection relationship of the transformer area and the branch parameters and current operating measurements; A multiphase voltage sensitivity model for the transformer area is constructed based on the topological connection relationship of the transformer area, branch parameters, and current operating measurements. A voltage approximation model is constructed based on the multiphase voltage sensitivity model of the transformer area.

[0010] The above scheme accurately quantifies the impact of changes in active and reactive power injection at nodes within the distribution area on the voltage of key nodes by first constructing a multiphase voltage sensitivity model of the distribution area and then constructing a voltage approximation model. This provides an accurate mathematical basis for voltage response for subsequent joint optimization and ensures that the optimization results can effectively improve the voltage quality of the distribution area.

[0011] Furthermore, the construction of the multiphase voltage sensitivity model for the transformer substation based on the substation topology, branch parameters, and current operating measurements includes: A three-phase power flow model for the transformer area is constructed based on the topological connection relationship of the transformer area, branch parameters, and current operating measurements. Based on the three-phase power flow model of the transformer area, obtain the reference node voltage data; The active power injection change and active voltage sensitivity coefficient are obtained based on the three-phase power flow model of the transformer area and the preset active power disturbance. Based on the three-phase power flow model of the transformer area and the preset reactive power disturbance, the reactive power injection change and reactive power voltage sensitivity coefficient are obtained. A multiphase voltage sensitivity model for the transformer area is constructed based on the changes in active power injection, active voltage sensitivity coefficient, reactive power injection, and reactive voltage sensitivity coefficient.

[0012] The above scheme obtains the reference node voltage data by constructing a three-phase power flow model of the transformer area, applies active and reactive disturbances respectively to calculate the corresponding sensitivity coefficients, and finally constructs a multiphase voltage sensitivity model to truly reflect the voltage response characteristics of the transformer area under actual operating conditions, thus avoiding the deviation between theoretical calculations and actual operation.

[0013] Furthermore, the step of obtaining the active power injection change and active power voltage sensitivity coefficient based on the three-phase power flow model of the transformer area and the preset active power disturbance includes: Based on the three-phase power flow model of the transformer area and the preset active power disturbance, active power disturbance is applied to all nodes in the transformer area to obtain the active power disturbance node voltage data. The active power injection change and active power voltage sensitivity coefficient are calculated based on the reference node voltage data, active power disturbance node voltage data, and preset active power disturbance amount.

[0014] The above scheme obtains the node voltage data after the disturbance by applying active power disturbance to all nodes in the transformer area. It calculates the change in active power injection and the active power voltage sensitivity coefficient by combining the reference node voltage data and the preset active power disturbance amount. It accurately quantifies and evaluates the impact of active power load transfer caused by phase switching on the voltage of each node, and provides a reliable quantitative basis for phase-specific scheduling optimization.

[0015] Furthermore, the step of obtaining the reactive power injection change and reactive power voltage sensitivity coefficient based on the three-phase power flow model of the transformer area and the preset reactive power disturbance includes: Based on the three-phase power flow model of the transformer area and the preset reactive power disturbance, reactive power disturbance is applied to all nodes in the transformer area to obtain the voltage data of the reactive power disturbance nodes. The reactive power injection change and reactive power voltage sensitivity coefficient are calculated based on the reference node voltage data, reactive power disturbance node voltage data, and preset reactive power disturbance amount.

[0016] The above scheme obtains the node voltage data after the disturbance by applying reactive power disturbance to all nodes in the transformer area. It calculates the reactive power injection change and reactive power voltage sensitivity coefficient by combining the benchmark node voltage data and the preset reactive power disturbance amount. This accurately assesses the degree of impact of the reactive power output of charging piles at different locations on the voltage of key nodes, providing a reliable quantitative basis for reactive power optimization scheduling.

[0017] Furthermore, the construction of the voltage approximation model based on the multiphase voltage sensitivity model of the transformer area includes: Obtain the charging pile node access data of all charging piles in the transformer area; A reactive power injection variation function is constructed based on phase access decision variables, reactive power decision variables, and charging pile node access data. A voltage approximation model is constructed based on the reactive power injection variation function and the multiphase voltage sensitivity model of the transformer area.

[0018] The above scheme obtains charging pile node access data, constructs a reactive power injection change function, and constructs a voltage approximation model by combining the multiphase voltage sensitivity model of the transformer area. It establishes a direct mapping relationship between the reactive power regulation of the charging pile and the voltage change of key nodes, directly transforming the reactive power regulation capability of the distributed charging piles into a quantitative expression of the global voltage support effect, thereby greatly simplifying the complexity of subsequent optimization calculations.

[0019] Furthermore, the method of obtaining the load-side three-phase imbalance index and several heavily loaded phase charging piles based on the transformer area topology and current operational measurements includes: Select several adjustable charging piles in the transformer substation that meet the preset coordination and control conditions, and obtain several active charging powers and several node access data corresponding to several adjustable charging piles based on the transformer substation topology connection relationship and current operation measurement. Three-phase base load data are obtained based on the current operating measurements. The total active load of the distribution area is obtained based on the three-phase basic load data and several active charging powers. Based on the total active power load of the transformer area, several heavy-load phase charging piles that meet the preset heavy-load phase conditions are selected. The load-side three-phase imbalance index is obtained based on the total active load of the transformer area, the access data of several nodes, and the phase access decision variables.

[0020] The above scheme obtains three-phase basic load data and total active load of the transformer area by screening adjustable charging piles that meet the preset coordination and control conditions, screening heavy-load phase charging piles and calculating the three-phase imbalance index on the load side. This accurately identifies the adjustable resources and three-phase load distribution status of the transformer area, narrows the optimization search space, effectively improves the computing efficiency of the edge terminal, and avoids the edge terminal being unable to solve the optimization problem in real time due to an excessively large search space, as well as the inability to distinguish between controllable and uncontrollable loads.

[0021] Furthermore, the step of acquiring several three-phase voltage phasors corresponding to several key nodes in the transformer area, and obtaining a voltage-side three-phase imbalance index based on the several three-phase voltage phasors, includes: Obtain several three-phase voltage phasors corresponding to several key nodes in the transformer area; For any critical node, the negative sequence voltage component and the positive sequence voltage component are calculated based on the three-phase voltage phasors, and the voltage imbalance of the critical node is calculated based on the negative sequence voltage component and the positive sequence voltage component. The voltage-side three-phase imbalance index is obtained based on the voltage imbalance degree corresponding to several key nodes.

[0022] The above scheme obtains the three-phase voltage phasors of key nodes, calculates the positive and negative sequence voltage components to obtain the voltage imbalance degree of each node, and finally constructs a voltage-side three-phase imbalance index to evaluate the degree of three-phase imbalance from the perspective of actual voltage response. This makes the treatment effect more in line with the actual power consumption experience of users and realizes the accurate reflection of the actual voltage quality of the transformer area based solely on load-side indicators.

[0023] Further, the step of obtaining a candidate phase-specific scheme set based on several of the heavy-load phase charging piles, and obtaining the phase-specific scheduling result and target reactive power adjustment amount based on the target constraints, the candidate phase-specific scheme set, and the joint optimization objective function, includes: A candidate phase-specific scheme set is obtained based on several of the aforementioned heavy-duty phase charging piles; The reactive power optimization objective function is obtained by performing inner-layer optimization decomposition on the joint optimization objective function; For any candidate phase access quantity in the candidate phase scheme set, the candidate reactive power adjustment quantity is obtained by solving the reactive power decision variable in the reactive power optimization objective function based on the preset reactive power optimization conditions. Based on the candidate reactive power adjustment quantities, target constraints, and preset output conditions corresponding to all candidate phase access quantities in the candidate phase scheme set, the phase access decision variables in the joint optimization objective function are solved to obtain the phase scheduling result. The candidate reactive power adjustment amount corresponding to the phase scheduling result is taken as the target reactive power adjustment amount.

[0024] The above scheme generates a set of candidate phase-specific schemes, decomposes the joint optimization objective function into two layers: inner reactive power optimization and outer phase-specific optimization. The candidate reactive power adjustment and the final phase-specific scheduling result are solved separately. This transforms the complex mixed-integer nonlinear programming problem into a quadratic programming problem and a finite search problem that can be solved quickly. This meets the real-time control requirements of the edge terminal and solves the technical problems that the joint optimization problem is difficult to solve, has a long computation time, and cannot be implemented in real time at the transformer substation or station control side.

[0025] This invention also provides a transformer substation voltage management system based on reactive power and phase balance, comprising: a voltage approximation module, an imbalance index calculation module, an objective function module, a constraint construction module, a scheme output module, and an instruction output module; wherein: The voltage approximation module is used to construct a voltage approximation model based on the pre-acquired transformer area topology connection relationship, branch parameters and current operating measurements; The imbalance index calculation module is used to obtain the load-side three-phase imbalance index and several heavily loaded phase charging piles based on the transformer area topology connection relationship and current operating measurements. The imbalance index calculation module is also used to obtain several three-phase voltage phasors corresponding to several key nodes in the transformer area, and to obtain the voltage-side three-phase imbalance index based on the several three-phase voltage phasors. The imbalance index calculation module is also used to obtain a three-phase imbalance evaluation index based on the load-side three-phase imbalance index and the voltage-side three-phase imbalance index. The objective function module is used to construct a joint optimization objective function based on the three-phase imbalance evaluation index and preset weight coefficients; The constraint construction module is used to construct target constraint conditions based on the voltage approximation model and preset constraint conditions; The scheme output module is used to obtain a candidate phase-specific scheme set based on a number of heavy-load phase charging piles, and to obtain the phase-specific scheduling result and the target reactive power adjustment amount based on the target constraints, the candidate phase-specific scheme set and the joint optimization objective function; The instruction output module is used to output executable instructions for the charging pile based on the phase scheduling results and the target reactive power adjustment. Attached Figure Description

[0026] To more clearly illustrate the technical solution of this application, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0027] Figure 1 This is a schematic diagram of a transformer substation voltage management method based on reactive power and phase balance provided in this embodiment; Figure 2 This is a schematic diagram of the complete execution process of a transformer area voltage management method based on reactive power and phase balance provided in this embodiment. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions of this application will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0029] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having”, and any variations thereof, in the specification, claims, and foregoing description of the drawings are intended to cover non-exclusive inclusion.

[0030] In the description of the embodiments of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly defined.

[0031] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0032] In the description of the embodiments in this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this document generally indicates that the preceding and following related objects have an "or" relationship.

[0033] In the description of the embodiments of this application, the term "multiple" refers to two or more (including two), similarly, "multiple sets" refers to two or more (including two sets), and "multiple pieces" refers to two or more (including two pieces).

[0034] In the description of the embodiments of this application, unless otherwise expressly specified and limited, technical terms such as "installation," "connection," "joining," and "fixing" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. For those skilled in the art, the specific meaning of the above terms in the embodiments of this application can be understood according to the specific circumstances.

[0035] Example 1: This embodiment provides a method for managing transformer substation voltage based on reactive power and phase balance, including: S1. Construct an approximate voltage model based on the pre-acquired transformer area topology, branch parameters, and current operating measurements; S2. Based on the topological connection relationship of the transformer area and the current operation measurement, the load-side three-phase imbalance index and several heavily loaded phase charging piles are obtained. S3. Obtain several three-phase voltage phasors corresponding to several key nodes in the transformer area, and obtain the voltage side three-phase imbalance index based on the several three-phase voltage phasors. S4. Obtain the three-phase imbalance evaluation index based on the load-side three-phase imbalance index and the voltage-side three-phase imbalance index; S5. Construct a joint optimization objective function based on the three-phase imbalance evaluation index and the preset weight coefficients; S6. Construct target constraints based on the voltage approximation model and preset constraints; S7. Based on several heavy-load phase charging piles, a candidate phase-specific scheme set is obtained, and based on the target constraints, the candidate phase-specific scheme set, and the joint optimization objective function, the phase-specific scheduling result and the target reactive power adjustment amount are obtained; S8. Output executable instructions for the charging pile based on the phase scheduling results and the target reactive power adjustment.

[0036] It should be noted that with the large-scale centralized connection of electric vehicle charging piles in low-voltage distribution areas, the strong randomness and time-varying characteristics of charging loads easily lead to a series of power quality problems such as undervoltage at the end nodes, local overvoltage, three-phase load imbalance, increased neutral current, and increased distribution area losses. Traditional solutions that rely on upgrading distribution transformers or installing centralized dedicated compensation devices have drawbacks such as large construction investment, long implementation period, high operation and maintenance costs, and difficulty in adapting to dynamic changes in charging loads. Moreover, existing charging piles are mostly regarded as uncontrollable pure power loads, and even those with basic power factor regulation functions often adopt a single-pile independent design. The current control mode lacks a global collaborative optimization mechanism, making it impossible to simultaneously address the multiple needs of voltage management, three-phase balance, user charging experience, and equipment safety and stability. Therefore, a collaborative management method for low-voltage distribution areas is needed to transform charging pile clusters from passive loads into actively adjustable distributed management resources. Without adding or with minimal addition of hardware, the reactive power output and phase balance adjustment behavior of charging piles can be uniformly scheduled through group control to suppress voltage overruns, reduce three-phase imbalance, reduce neutral current and distribution area losses, and simultaneously ensure user charging completion and equipment safety and stability.

[0037] This embodiment provides a method for managing transformer voltage based on reactive power and phase balance, which is applied to the coordinated operation control process of electric vehicle charging facilities and power distribution networks. In particular, it relates to a method for jointly managing transformer voltage and three-phase imbalance by utilizing the reactive power regulation capability and phase balance regulation capability of the grid-connected side of the charging pile group in low-voltage transformer areas. First, operational information such as three-phase voltage, current, power, and key node voltage is collected at the transformer substation side. Real-time charging power, available reactive power capacity, phase configuration, and phase adjustability of the charging pile group are obtained. An approximate model or sensitivity model between multi-phase voltage and power injection in the transformer substation is established. Based on this, with voltage qualification constraints and three-phase imbalance suppression as the core objectives, the reactive power setpoint of the charging pile group and the phase allocation or phase switching scheme of adjustable phase charging tasks are jointly solved. The calculation results are then sent to the charging piles or station control devices for execution in the form of power factor commands, reactive power commands, droop curve parameters, and phase scheduling commands. The method also considers engineering constraints such as the apparent capacity boundary of the charging piles, reactive power ramp-up, number of phase switching and minimum interval, communication anomaly degradation operation, and user charging demand protection. Thus, under the conditions of load fluctuation and random access of electric vehicles, the method achieves coordinated closed-loop control of transformer substation voltage management and phase balance management, effectively reducing the risk of end-point undervoltage, reducing three-phase imbalance, and neutral current.

[0038] In the specific implementation process, this embodiment first defines variables and constructs the transformer area status, assuming the transformer area node set is as follows: Each node is k, and the set of branches is . The three phases of the transformer area are respectively denoted as... At that moment The collected node voltage per unit value is denoted as , The net injected active power and net injected reactive power at the node are denoted as follows: , The group of all charging stations in the area is denoted as . , No. The real-time active charging power of the charging pile is , Rated grid-connected capacity is The unproductive factors awaiting decision-making are (That is, the reactive power decision variable). If the charging pile is connected to a single phase, then it is a single-phase charging pile, and its connection phase is represented by a binary variable. , indicating the first Taiwan single-phase charging pile at time The phases of the decision variables are respectively connected, satisfying the following constraints: ; Among them, when the first Taiwan charging pile at all times Access phase hour, ,otherwise, The above constraint means that a single-phase charging pile can only be connected to one of the three phases (A, B, and C) at the same control time. For charging piles with phase switching capabilities, These are the decision variables to be optimized (i.e., the phase access decision variables). For fixed-phase charging piles, The value is fixed as the engineering configuration value and is a known constant. For a three-phase charging pile, its phase active power can be denoted as... It satisfies the following constraints: ; in, Indicates the first Taiwan three-phase charging pile at time Assigned to different The single-phase active charging power on the device, Indicates the first Taiwan charging pile at all times Total active charging power. If the three-phase charging pile does not have phase-by-phase adjustment capability, then , , The power allocation can be determined according to the default power distribution of the equipment; if the three-phase charging pile has the ability to adjust each phase, the power of each phase can be used as a control variable to participate in the optimization within the allowable range of the equipment, and the upper and lower limits of each phase can be set to reflect its controllability.

[0039] The total charging power of each phase in the distribution area is constructed using binary variables based on the active charging power and the connected phase, as shown in the following formula: ; in, Indicates time All charging piles within the area that participate in the coordinated control are in phases. The total active charging power generated is calculated. The calculation process of the total charging power of each phase in this area is used to statistically analyze the active load distribution of the charging pile cluster on each of phases A, B, and C, providing input for subsequent phase balance optimization.

[0040] Next, this embodiment constructs the total reactive power contribution of each transformer area phase using binary variables based on the reactive power decision variable and the connected phase: ; in, Indicates time The charging pile clusters within the area are located in different sections. The total reactive power regulation formed above; Indicates the first Taiwan charging pile at all times The reactive power setpoint or actual output value (i.e., the reactive power decision variable) is used to describe the distribution of the reactive power regulation capability of the charging pile group on each phase.

[0041] Optionally, step S1 includes: Obtain the topology connection relationship of the transformer area and the branch parameters and current operating measurements; A multiphase voltage sensitivity model for the transformer area is constructed based on the topological connection relationship of the transformer area, branch parameters, and current operating measurements. A voltage approximation model is constructed based on the multiphase voltage sensitivity model of the transformer area.

[0042] In the specific implementation process, this embodiment first obtains the topological connection relationship and branch parameters of the distribution system in the distribution area. The branch parameters include the resistance and reactance parameters of each phase of the distribution line. Measurement information including the three-phase voltage, three-phase current, three-phase total active power, and three-phase total reactive power of the distribution area are collected from the low-voltage side outlet of the distribution transformer or the total power meter of the distribution area. Sampling data of each phase voltage are collected from a pre-selected set of key nodes (such as key end nodes or representative nodes). Real-time operating status and regulation capability parameters of all charging piles in the distribution area are collected from the station control system or each charging pile terminal, including real-time charging active power, current available apparent capacity, upper and lower limits of reactive power regulation, and hardware attribute identifiers such as whether it has the ability to switch between live phases and the ability to independently control three-phase power. All the above-mentioned collected data are processed by time-scale alignment, outlier removal, missing data completion, and consistency verification to generate standardized current operating measurements including the distribution area operating status vector and the charging pile group resource capability vector for subsequent optimization calculations.

[0043] Optionally, the step of constructing a multiphase voltage sensitivity model for the transformer substation based on the substation topology, branch parameters, and current operating measurements includes: A three-phase power flow model for the transformer area is constructed based on the topological connection relationship of the transformer area, branch parameters, and current operating measurements. Based on the three-phase power flow model of the transformer area, obtain the reference node voltage data; The active power injection change and active voltage sensitivity coefficient are obtained based on the three-phase power flow model of the transformer area and the preset active power disturbance. Based on the three-phase power flow model of the transformer area and the preset reactive power disturbance, the reactive power injection change and reactive power voltage sensitivity coefficient are obtained. A multiphase voltage sensitivity model for the transformer area is constructed based on the changes in active power injection, active voltage sensitivity coefficient, reactive power injection, and reactive voltage sensitivity coefficient.

[0044] In this embodiment, for low-voltage radial distribution lines, a multi-phase voltage sensitivity model based on the distribution area topology, branch parameters, and current operational measurements is preferably adopted to establish an approximate relationship between node voltage changes and changes in active and reactive power injection at the nodes. This multi-phase voltage sensitivity model describes the changes in critical node voltages when the active load, reactive power output, or phase allocation of charging piles within the distribution area changes. The set of critical nodes is denoted as... At that moment ,node Parting The voltage change on is denoted as ,node Parting The changes in active power injection and reactive power injection are denoted as follows: , The multiphase voltage sensitivity model for the transformer substation can then be expressed as follows: ; in, Represents a node Parting voltage to node Parting The active voltage sensitivity coefficient for changes in active power injection; Represents a node Parting voltage to node Parting The reactive voltage sensitivity coefficient for reactive power injection changes. This sensitivity coefficient characterizes the impact of power changes at a certain node or phase within a transformer substation on the voltage at another node or phase. If the inter-phase coupling within the substation is weak, or to reduce the complexity of edge computing, the cross-influence between different phases can be ignored. Therefore, in this embodiment, the above model is simplified as shown in the following equation: .

[0045] Optionally, obtaining the active power injection change and active power voltage sensitivity coefficient based on the three-phase power flow model of the transformer area and the preset active power disturbance includes: Based on the three-phase power flow model of the transformer area and the preset active power disturbance, active power disturbance is applied to all nodes in the transformer area to obtain the active power disturbance node voltage data. The active power injection change and active power voltage sensitivity coefficient are calculated based on the reference node voltage data, active power disturbance node voltage data, and preset active power disturbance amount.

[0046] Optionally, obtaining the reactive power injection change and reactive power voltage sensitivity coefficient based on the three-phase power flow model of the transformer area and the preset reactive power disturbance includes: Based on the three-phase power flow model of the transformer area and the preset reactive power disturbance, reactive power disturbance is applied to all nodes in the transformer area to obtain the voltage data of the reactive power disturbance nodes. The reactive power injection change and reactive power voltage sensitivity coefficient are calculated based on the reference node voltage data, reactive power disturbance node voltage data, and preset reactive power disturbance amount.

[0047] In this embodiment, and These are not fixed parameters that are arbitrarily set in advance, but are calculated or identified based on data such as the transformer topology, line impedance parameters, transformer parameters, real-time voltage measurements at nodes, active / reactive power measurements at nodes, and the location of charging piles.

[0048] Preferably, this embodiment employs a sensitivity acquisition method based on perturbation trial calculation, the specific process of which is as follows: First, based on the branch parameters, the branch... The phase-splitting resistance and phase-splitting reactance are respectively denoted as , ,in This represents a power distribution line connecting node m and node n in the transformer area. This represents the set of transformer substation branches in the branch parameters. Current operating measurements include node voltages. Active power at nodes Node reactive power Active power of charging piles The data includes the non-functional capacity boundary of the charging pile, as well as the node and phase information of the charging pile. It should be noted that the above data are all obtained directly from the main distribution meter, branch monitoring terminal, end voltage monitoring device, charging station control system, or charging pile communication interface, etc.

[0049] Secondly, using the current operating state as the baseline operating point, a three-phase power flow model for the transformer area is established based on the transformer area topology, branch parameters, and current operating measurements. This model could be a three-phase power flow calculation model or a linearized power flow approximation model, to obtain the voltage of each phase at each node under the baseline state. (i.e., the reference node voltage data).

[0050] Then, in the three-phase power flow model of the transformer area, the nodes are... Parting Apply a small active disturbance (i.e., the preset active power disturbance), keeping the power of other nodes unchanged, recalculate the node voltage after the disturbance. (i.e., the active power disturbance node voltage data), and calculate the active power voltage sensitivity coefficient according to the following formula: ; In this embodiment, the active voltage sensitivity coefficient is used to represent the effect of a unit change in active power injection on the change in node voltage.

[0051] Similarly, in the three-phase power flow model of the transformer area, nodes... Parting Apply a small reactive power disturbance (i.e., the preset reactive power disturbance), keeping the power of other nodes unchanged, recalculate the node voltage after the disturbance. (i.e., the reactive power disturbance node voltage data), and calculate the reactive power voltage sensitivity coefficient using the following formula: ; In this embodiment, the reactive voltage sensitivity coefficient is used to represent the effect of a unit change in reactive power injection on the change in node voltage.

[0052] The above disturbance amount , The per-unit disturbance can be set to a small amplitude based on the rated capacity of the distribution area, the load level of the node, or the rated capacity of the charging pile. The disturbance should be small enough to ensure linear approximation effectiveness; at the same time, it should be greater than the voltage fluctuation caused by measurement noise to ensure the identifiability of the sensitivity calculation results. In practical applications, a certain proportion of the rated capacity of the node phase or the reference capacity of the distribution area can be taken as the disturbance amplitude.

[0053] If the transformer substation topology and line parameters remain unchanged over a long period, a basic sensitivity matrix can be pre-calculated offline and corrected during operation based on real-time voltage, load levels, and switch status. If the substation operating mode, charging pile access status, or branch switch status changes, the sensitivity matrix is ​​recalculated or updated online. Therefore, and It can be pre-stored as model parameters in the transformer area controller, or it can be updated periodically according to the operating status; it is not an unchangeable fixed constant.

[0054] Optionally, the step of constructing a voltage approximation model based on the multiphase voltage sensitivity model of the transformer area includes: Obtain the charging pile node access data of all charging piles in the transformer area; A reactive power injection variation function is constructed based on phase access decision variables, reactive power decision variables, and charging pile node access data. A voltage approximation model is constructed based on the reactive power injection variation function and the multiphase voltage sensitivity model of the transformer area.

[0055] In this embodiment, in order to establish the relationship between the reactive power regulation of the charging pile and the voltage change of the key node, the reactive power regulation of the charging pile is mapped to the reactive power injection change of the node.

[0056] First, this embodiment Indicates charging station With nodes Given the node access relationships (i.e., the phase access decision variables), we have: ; in, Taiwan charging pile access node hour, ,otherwise ; Indicates the first Taiwan charging pile at all times Whether to connect to the phase That is, for fixed charging piles, When the topology of the charging station area remains unchanged, these are pre-configured fixed parameters, which are included in the charging pile node access data and are typically obtained from the charging pile installation log, station control system configuration file, or charging station area topology modeling data. When the charging pile access point, charging station topology, or station control system configuration changes, Update with configuration.

[0057] Under the reactive power regulation effect of charging piles based on reactive power decision variables, the node Parting The change in reactive power injection can be expressed as the reactive power injection change function shown in the following equation: ; in, Represents a node At parting The change in reactive power injection caused by the reactive power regulation of the charging pile; Indicates the first The change in reactive power of a charging pile relative to the reactive power of the previous control cycle or the baseline operating point. This reactive power injection variation function is used to map the reactive power adjustment of a single charging pile to its respective substation node and phase.

[0058] Based on the reactive power injection variation function, the sensitivity of node voltage to the reactive power of charging piles is obtained, and the following approximate voltage model is constructed: ; in, , Indicates the first Taiwan charging piles in different phases Reactive power regulation on nodes Parting The equivalent influence coefficient of voltage; Represents a node Voltage to node At parting The reactive voltage sensitivity coefficient of reactive power injection variation; Indicates the first Taiwan charging piles and nodes Node access relationships; This represents the voltage change term caused by factors such as user load fluctuations, distributed power source fluctuations, or measurement disturbances, excluding the reactive power regulation of charging piles. This embodiment establishes an approximate linear relationship between the reactive power regulation of charging piles and the voltage changes at key nodes using this voltage approximation model.

[0059] Prioritizing the effectiveness of end-of-pipe treatment, this embodiment selects only the set of key nodes as the objects of voltage constraints and target evaluation during the construction of the voltage approximation model.

[0060] Optionally, step S2 includes: Select several adjustable charging piles in the transformer substation that meet the preset coordination and control conditions, and obtain several active charging powers and several node access data corresponding to several adjustable charging piles based on the transformer substation topology connection relationship and current operation measurement. Three-phase base load data are obtained based on the current operating measurements. The total active load of the distribution area is obtained based on the three-phase basic load data and several active charging powers. Based on the total active power load of the transformer area, several heavy-load phase charging piles that meet the preset heavy-load phase conditions are selected. The load-side three-phase imbalance index is obtained based on the total active load of the transformer area, the access data of several nodes, and the phase access decision variables.

[0061] In the specific implementation process, this embodiment will be in constant motion. Parting The total active load of the transformer substation is expressed as follows: ; in, Indicates time Taiwan District in Separation Total active power load; Indicates separation The sum of the basic load or non-charging load other than the charging piles and the total active charging load of the charging piles that do not participate in the coordinated control is included in the three-phase basic load data. The three-phase basic load data can be obtained from the transformer area measurement data, user-side collected data or state estimation methods. Indicates separation The above refers to the total coordinated active charging load formed by all charging piles participating in the coordinated control in the charging pile group, that is, the sum of the active charging power contributed by all charging piles participating in the coordinated control in the transformer area on this phase.

[0062] For scenarios where single-phase and three-phase charging piles are mixed, This can be further expressed as follows: ; in, This refers to the collection of single-phase charging piles within the transformer substation that participate in coordinated control. This refers to the set of three-phase charging piles within the transformer area that participate in coordinated control. Indicates the first Taiwan single-phase charging pile at time Whether to connect to the phase ; Indicates the first Taiwan single-phase charging pile at time The active charging power; Indicates the first The three-phase charging piles are assigned to different phases. The active charging power. If all charging piles involved in the control of the transformer area are treated according to the single-phase equivalent model, the above formula can be simplified to: ; in, This represents the set of charging stations participating in the coordinated control.

[0063] Based on the above calculation process, , and Subsequently, the three-phase active power load deviation can be used to construct the load-side three-phase imbalance index. This embodiment is based on... , and The coordinated three-phase average active load was calculated. The process is shown in the following formula: ; The three-phase imbalance index on the load side can be expressed as follows: ; in, Indicates time Load-side three-phase imbalance index based on three-phase active power load deviation; , , These represent the coordinated total active charging load of phases A, B, and C, respectively. The larger the value, the more significant the deviation of the three-phase load from the average value, and the higher the degree of three-phase load imbalance. The smaller the value, the closer the three-phase load is to balance.

[0064] The load-side imbalance index obtained in this embodiment It is mainly used to describe whether the three-phase active load distribution is balanced and to provide a basis for phase allocation or phase switching. For example, when the total active load of a certain phase is significantly higher than that of the other two phases, that phase can be identified as a heavily loaded phase; when the total active load of a certain phase is significantly lower than that of the other two phases, that phase can be identified as a lightly loaded phase. For charging piles with phase-adjustable capabilities, it is advisable to prioritize adjusting some charging tasks from the heavily loaded phase to the lightly loaded phase, thereby reducing the three-phase load deviation. Therefore, this embodiment selects several heavily loaded phase charging piles that meet the preset heavy-load phase conditions based on the total active load of the transformer area.

[0065] In practical implementation, this embodiment represents the currently loaded phase as shown in the following formula: ; The light-load phase at the current moment can be expressed as follows: ; When the Taiwan-made phase-switching charging piles are made of heavy-duty phases Switch to light-load phase At that time, the charging power of each phase in the distribution area can be updated accordingly: ; ; in, This represents the total active charging power on the reloaded phase after phase switching. This represents the total active charging power on the lightly loaded phase after phase switching. This process shows that phase adjustment does not reduce the user's charging power, but rather changes the phase assignment of some adjustable charging piles under the premise of meeting equipment switching constraints and user charging needs, thereby improving the distribution of three-phase active load in the distribution area.

[0066] It should be noted that the preset heavy load phase condition is the phase heavy load determination condition, that is, the target adjustment phase is selected, the total active load of the target adjustment phase is the maximum value of the total active load of the three phases, and the deviation of the load of the target phase from the average active load of the three phases exceeds the preset unbalance start threshold. The charging pile with the target adjustment phase as the heavy load phase is selected to generate a candidate phase scheme set.

[0067] Optionally, step S3 includes: Obtain several three-phase voltage phasors corresponding to several key nodes in the transformer area; For any critical node, the negative sequence voltage component and the positive sequence voltage component are calculated based on the three-phase voltage phasors, and the voltage imbalance of the critical node is calculated based on the negative sequence voltage component and the positive sequence voltage component. The voltage-side three-phase imbalance index is obtained based on the voltage imbalance degree corresponding to several key nodes.

[0068] In practical implementation, since three-phase load imbalance is reflected in the voltage drop of low-voltage lines as asymmetry in the amplitude and phase angle of the three-phase voltages, a voltage-side three-phase imbalance index can be constructed based on the negative sequence components of the three-phase voltages, provided that three-phase voltage phasor measurement conditions are available or the three-phase voltage phasors can be obtained through state estimation. This index is similar to the aforementioned load-side three-phase imbalance index. The difference is: The three-phase load distribution perspective evaluates the degree of imbalance and is suitable for guiding phase-specific adjustments; the negative voltage sequence index evaluates the degree of imbalance from the perspective of the actual three-phase voltage response and is suitable for reflecting the final voltage quality.

[0069] For key nodes in the key node combination Let its three-phase voltage phasors be respectively , , ,make Then the node The negative sequence voltage component can be expressed as: ; The corresponding positive sequence voltage component can be expressed as: ; in, , , These represent key nodes. At any moment The A, B, and C phase voltage phasors; This represents the rotation factor in the three-phase symmetric component transformation; Represents a node The negative sequence voltage component; Represents a node The positive sequence voltage components. It should be noted that the three-phase voltage phasors can be obtained from the voltage monitoring device at the end of the distribution area, the three-phase measurement device on the low-voltage side of the distribution transformer, or the monitoring terminal with phase angle estimation capability, or they can be estimated by the distribution area state estimation algorithm based on the three-phase voltage, current and power measurement data.

[0070] Next, based on the positive and negative sequence voltage components, nodes are defined. The voltage imbalance is: ; The voltage imbalance is expressed as a percentage: ; in, Represents a node Voltage imbalance This represents the magnitude of the negative sequence voltage component. This represents the magnitude of the positive-sequence voltage component. It should be noted that... The larger the value, the more likely it is to be a node. The more unbalanced the three-phase voltage; The smaller the value, the closer the three-phase voltage is to equilibrium.

[0071] In practical implementation, if multiple key nodes are used as evaluation objects as shown in this embodiment, a three-phase imbalance index on the voltage side can be constructed based on the above voltage imbalance, as shown in the following formula: ; in, This represents a voltage-side imbalance evaluation index constructed based on the negative sequence component of the key node voltage. Indicates key nodes The evaluation weights can be set based on the node voltage sensitivity, user importance, historical over-limit frequency, or end location.

[0072] Preferably, if only one representative node is selected for evaluation, then You can directly retrieve the node's... or .

[0073] In practical implementation, the calculation method for the three-phase imbalance index can be selected based on the measurement conditions and control objectives of the transformer substation. Specifically: when the transformer substation only has three-phase power measurement, charging pile power acquisition, and phase status information, but lacks reliable three-phase voltage phasor measurement conditions, the following method can be adopted: As a three-phase imbalance evaluation index; when the transformer substation has key node three-phase voltage phasor measurements, or when the three-phase voltage phasors can be obtained through state estimation, it can be used. As a three-phase imbalance evaluation index; when the transformer area has both three-phase power data and three-phase voltage phasor data, the load-side imbalance index and the voltage-side imbalance index can be weighted and combined to construct a comprehensive imbalance index as shown in the following formula as a three-phase imbalance evaluation index: ; in, This represents the comprehensive three-phase imbalance index used for joint optimization; This represents the normalized load-side three-phase imbalance index; This indicates the three-phase imbalance index on the voltage side; and These represent the weights of the load-side three-phase imbalance index and the voltage-side three-phase imbalance index, respectively.

[0074] It should be noted that, through settings Load-side indicators can be used independently; by setting Voltage-side indicators can be used independently; by setting them simultaneously... It can simultaneously achieve balanced three-phase load distribution and improved three-phase voltage quality.

[0075] Among them, the normalized load-side imbalance index It can be expressed in the form shown below: ; in, A small positive number is set to prevent the denominator from being zero. This normalization process is used to eliminate the problem of different dimensions between load-side indicators and voltage-side indicators, making it easier to combine them in the same objective function with weights.

[0076] Optionally, step S7 includes: A candidate phase-specific scheme set is obtained based on several of the aforementioned heavy-duty phase charging piles; The reactive power optimization objective function is obtained by performing inner-layer optimization decomposition on the joint optimization objective function; For any candidate phase access quantity in the candidate phase scheme set, the candidate reactive power adjustment quantity is obtained by solving the reactive power decision variable in the reactive power optimization objective function based on the preset reactive power optimization conditions. Based on the candidate reactive power adjustment quantities, target constraints, and preset output conditions corresponding to all candidate phase access quantities in the candidate phase scheme set, the phase access decision variables in the joint optimization objective function are solved to obtain the phase scheduling result. The candidate reactive power adjustment amount corresponding to the phase scheduling result is taken as the target reactive power adjustment amount.

[0077] In the specific implementation process, for each control cycle (starting from the current time t) (Internal), construct a joint objective function to simultaneously improve voltage compliance and phase balance, and control operating costs and user impact.

[0078] Preferably, this embodiment introduces a voltage over-limit relaxation variable. The joint optimization objective function is constructed as shown in the following equation: ; in, This represents the joint optimization objective function for the current control cycle; Indicates the first The reactive power decision variable of a charging pile; Indicates the first The phase connection decision variables of each charging pile; and Representing nodes respectively Parting Non-negative relaxation variables for voltage upper and lower limits; Indicates the first A binary variable indicating whether a phase switch occurs at a charging pile during the current control cycle. If the phase changes, then Select 1 if the condition is not met, otherwise select 0. , , , These represent the weights for voltage over-limit penalties, three-phase imbalance penalties, reactive power smoothing penalties, and phase switching penalties, respectively. The first term on the right-hand side of the equation... The second item is for voltage over-limit penalty. The third item is a penalty for imbalance. For reactive power smoothing, the fourth term For the cost of phase cutting, These are the weighting coefficients.

[0079] This embodiment constructs preset constraint conditions based on the functional limit and dynamic constraints of charging piles. These preset constraint conditions include node voltage over-limit constraints for the charging station area. Specifically, the node voltage over-limit constraints in this embodiment are used to ensure that the voltage of critical nodes is within the allowable operating range, and can be expressed as follows: ; in, Represents a node At parting The per-unit voltage value or actual voltage value; This indicates the lower limit of the allowable voltage for the transformer area; This indicates the maximum allowable voltage for the transformer area.

[0080] Preferably, to ensure the solvability of the optimization problem in extreme cases, this embodiment introduces relaxation variables to rewrite the node voltage over-limit constraint equivalently as shown in the following equation: ; in, Represents a node Parting Voltage exceeds the upper limit The upper limit of relaxation amount at that time; Represents a node Parting Voltage below the lower limit The lower limit of relaxation at that time.

[0081] It should be noted that after introducing slack variables, the optimization problem remains solvable even when the charging pile's functional capacity is insufficient or its phase adjustment capability is limited, and the penalty term in the objective function minimizes the voltage exceedance as much as possible. Then, substituting the voltage approximation model from the previous section into the above constraints, we obtain the following... The constraint expression is used to obtain the target constraint conditions.

[0082] The preset constraints also include the charging pile's reactive power capacity boundary and dynamic constraints. In this embodiment, the charging pile's reactive power capacity boundary and dynamic constraints include the charging pile's capacity circle constraint, the charging pile's reactive power ramp-up constraint, user demand protection constraints, and window power constraints, etc. Among them: First, the active and reactive power of all charging piles in the distribution area are limited by the apparent capacity of the equipment. To prevent reactive power adjustment commands from causing charging piles to operate beyond their own capacity limits, the rated grid-connected apparent capacity should meet the capacity circle constraint shown in the following formula: ; Based on the above capacity circle constraint, the reactive power feasible region is obtained as shown in the following equation: ; in, Indicates the first The charging piles in Taiwan currently have the following active charging power. The maximum positive reactive power that can be provided is This indicates the minimum reactive power it can provide, i.e., the maximum reverse reactive power. This reactive power feasible region is determined by the rated apparent capacity of the charging pile. With real-time active power The following consensus was reached: The apparent power constraints of the power electronic converter must be followed: reactive power output must not exceed its current available reactive power capacity boundary; the closer the active charging power of the charging pile is to its rated capacity, the smaller the remaining capacity available for reactive power regulation; for charging piles with symmetrical capacitive and inductive reactive power regulation capabilities, the lower limit of reactive power regulation is the opposite of the upper limit; for charging piles with asymmetrical capabilities, the upper and lower limits of reactive power regulation can be given by the equipment's factory capacity curve or parameters obtained in real time through the communication interface.

[0083] Secondly, to suppress rapid fluctuations in reactive power, this embodiment also introduces the reactive power ramping constraint of the charging pile as shown in the following formula, to ensure that the change range of the reactive power command of the charging pile does not exceed the reactive power ramping capacity allowed by the equipment: ; in, This indicates the reactive power setpoint from the previous control cycle. Indicates the first The upper limit of the reactive power variation rate allowed for a charging pile in Taiwan. The control cycle is indicated, and in this embodiment, it is executed within each control cycle. The reactive power ramp-up constraint of the charging pile is used to limit the change in reactive power command between two adjacent control cycles, so as to avoid voltage fluctuations, frequent equipment adjustments, or control oscillations caused by sudden changes in reactive power output.

[0084] Next, user demand protection constraints can be added to the preset constraints according to the site requirements. For example, a minimum charging power for users can be guaranteed to ensure that voltage regulation and phase balance adjustment do not excessively sacrifice the user's basic charging needs, as shown in the following formula: ; in, Indicates the first Taiwan charging pile at all times The minimum active charging power required can be determined based on user reservation needs, battery state of charge, estimated departure time, or station control system strategy.

[0085] Alternatively, a window charge constraint as shown in the following formula can be introduced to ensure that within the window... Complete the power requirement within: ; in, This indicates the available charging time window for the user's vehicle when connected to the charging station. Indicates the first Taiwan charging pile at all times Active charging power, Indicates the length of the control cycle. This represents the minimum amount of charging power a user expects to receive within this time window. This constraint ensures that the user's vehicle receives the required cumulative charging power throughout the entire charging time window.

[0086] In the conventional implementation of this solution, the current active charging power of the charging pile can be collected in real time by the charging pile or the station control system. The window power constraint is used to determine whether there is a risk that the charging task cannot be completed on schedule based on the current charging power, predicted charging power, remaining charging time, and user demand. If the constraint is not met, the controller triggers user demand protection actions, including increasing the charging priority of the charging pile, prohibiting phase switching actions that would cause charging interruption or power reduction, canceling or relaxing its participation in active power limiting, and prioritizing the use of the reactive power regulation capabilities or phase regulation capabilities of other charging piles to complete the voltage management of the distribution area. If the voltage safety constraint still cannot be met without sacrificing the user's basic charging needs, then degraded operation or alarm processing will be initiated.

[0087] Furthermore, to transform the nonlinear phase-cutting action determination into a linear constraint and the phase-switching behavior into the action cost in the joint optimization objective function, this embodiment introduces a phase-cutting action auxiliary binary variable. And construct a tangent phase constraint, assuming the previous period phase is respectively The tangent constraint between the phase and the phase access variables can be expressed by the following linear inequality: ; in, For the first A binary variable indicating whether a phase switch occurs at a charging pile during the current control cycle; control cycle. This indicates the time interval at which the area controller performs one optimization calculation. When the... Phase connection status of the charging pile in the current cycle Phase-to-connection status compared to the previous cycle When inconsistent, A value of 1 indicates that a phase switch has occurred at the charging station; when the phase does not change, the phase switching penalty term in the objective function applies. Take 0.

[0088] Based on this, to avoid frequent phase switching of charging piles, this embodiment also sets a minimum phase-switching interval constraint, setting... This is the last time the phase was switched. At the current moment, the minimum interval constraint for phase switching of the charging pile is: satisfying... The time indicates that commutation is permitted, where For the first The minimum allowable phase switching time interval between two phase switching operations of a phase-switching charging pile.

[0089] If discrete control periodic representation is used, the above constraints can be equivalently written as shown in the following equation: ; ; in, Indicates the current control cycle number; Indicates the first The control cycle number corresponding to the last phase switch of the charging pile; This indicates the number of control cycles corresponding to the minimum phase-cutting time interval; This indicates the rounding up operation.

[0090] In one specific embodiment, if the control cycle of the transformer area is... Take 5 minutes, the first Minimum commutation interval of a phase-switching charging pile Take 30 minutes, then That is, the same phase-switching charging pile is only allowed to perform phase switching again after at least 6 control cycles. In other implementations, The time limit can be set from 15 minutes to 60 minutes, preferably 30 minutes, depending on the lifespan of the charging pile's phase switching device, station control strategy, user charging continuity requirements, and the degree of imbalance in the charging area. For charging piles that use mechanical contactors to perform phase switching, switching should be performed only after the charging current drops below the allowable switching threshold to reduce the impact on the equipment and the user's charging process.

[0091] During the calculation of the joint optimization objective function, the phase constraint and the minimum phase interval constraint can be achieved by disabling variables or increasing the penalty.

[0092] This embodiment employs a disabled variable method. Specifically, when obtaining a candidate phase scheme set based on several heavily loaded phase charging piles, this embodiment introduces charging pile switchability determination conditions. These conditions require selecting charging piles with both live phase switching and reactive power regulation capabilities. Specifically, the charging pile must not be currently in a commutation cooling lockout period, i.e., satisfying the minimum phase-switching interval constraint; the cumulative number of phase commutations per day must not have reached a preset upper limit; the aforementioned phase-switching constraint must be satisfied; the real-time charging active power must be greater than a preset minimum switching power threshold, and the charging pile must not be set to a prohibited switching mode by the user. Based on these charging pile switchability determination conditions, charging piles meeting the conditions are selected from several heavily loaded phase charging piles to generate the candidate phase scheme set.

[0093] In the specific implementation process, to reduce computational complexity and adapt to edge computing resources in the transformer substation area, this embodiment adopts a two-layer solution structure of phase allocation outer layer search and reactive power dual-layer optimization to solve the joint objective function. First, the phase allocation outer layer search is performed, that is, the outer layer generates a finite number of phase allocation schemes within the set of candidate charging piles that meet the charging pile switchability determination conditions. This generates a set of candidate phase allocation schemes. Then, a two-layer solution structure for reactive power optimization is implemented: the inner layer solves for candidate reactive power adjustments under fixed phase allocation schemes within the candidate phase allocation scheme set, while the outer layer provides a given phase allocation scheme. Under these conditions, the reactive power of each charging pile Continuous optimization is performed; the outer layer solves for the target reactive power adjustment based on the candidate reactive power adjustment.

[0094] When performing reactive power optimization at both the inner and outer layers, since the phase variables are fixed in the inner layer problem, this embodiment transforms the inner layer optimization problem into a quadratic programming problem concerning reactive power, thereby improving the real-time solution efficiency of the transformer edge controller. The primary programming solution process involves the inner layer performing inner-layer optimization decomposition on the joint optimization objective function to obtain the reactive power optimization objective function, as shown in the following equation: ; in, Used to reduce the degree of voltage exceedance at critical nodes Used to suppress drastic changes in reactive power between adjacent control cycles.

[0095] In a planning and solving process, for any candidate phase connection quantity in the candidate phase scheme set, the reactive power decision variable in the reactive power optimization objective function is determined based on preset constraints. The candidate reactive power adjustment values ​​are obtained by solving the problem.

[0096] Next, the outer quadratic programming solution process is performed. The quadratic programming solution process involves calculating the comprehensive cost for each candidate solution in the candidate phase solution set, as shown in the following formula: ; in, This represents the comprehensive cost corresponding to a certain candidate phase scheme (i.e., the access volume of a certain candidate phase in the candidate phase scheme set); This represents the reactive power optimization objective function value corresponding to the candidate reactive power adjustment amount obtained in the next planning and solving process of the candidate phase scheme; This indicates the three-phase imbalance evaluation index corresponding to the candidate phase scheme; and These represent the three-phase imbalance penalty weight and the phase switching penalty weight, respectively. The outer layer optimization compares different candidate phase switching schemes... The scheme with the lowest overall cost is selected as the final phase scheduling result.

[0097] It should be noted that several candidate phase schemes in the candidate phase scheme set can be generated by the principle of prioritizing the phase with the greatest imbalance. For example, the phase with the heaviest load can be moved to the lightest phase to form a finite number of alternatives to ensure real-time performance.

[0098] After solving the joint optimization objective function as described above, obtaining the phase scheduling results and target reactive power adjustment amount, instructions are generated, limited, and issued. First, the optimal solution target reactive power adjustment amount is... Convert to executable commands for the charging station. If the charging station supports direct reactive power setting, then issue the command. If direct reactive power setting is not supported, and only power factor setting is supported, then the following power factor command will be issued: ; in, The first term obtained by optimization solution is represented as... Taiwan charging pile at all times The target reactive power adjustment amount This represents the optimal power factor setting value corresponding to the reactive power command. For charging piles that only support power factor control, the optimal reactive power command corresponding to the target reactive power adjustment can be converted into a power factor command according to this formula; simultaneously, according to... The sign of the power factor determines whether it is leading or lagging.

[0099] Prioritize charging piles with adjustable phases, and implement the target phase distribution accordingly. or binary variable Beforehand, a second safety check is performed: if the measured voltage is near the threshold, a dead zone and hysteresis are superimposed on the reactive power command to avoid jitter; the minimum interval and maximum number of times for the phase switching command are checked, and if they are not met, the system reverts to the reactive power management strategy only.

[0100] Optionally, after step S7, the following steps are also included: Obtain actual operating data of the transformer area within the preset evaluation window; Calculate voltage over-limit evaluation index and imbalance index based on the actual operating data of the aforementioned transformer area; Based on the voltage over-limit evaluation index and the imbalance index, the parameters are adaptively adjusted.

[0101] In its implementation, this embodiment introduces the aforementioned closed-loop evaluation and adaptive parameter update mechanism. After issuing and executing executable commands for the charging pile, including phase-cutting and reactive power injection commands, in each control cycle, actual operating data of the transformer substation after command execution is collected through a preset evaluation window (such as a sliding time window). This actual operating data includes the current node voltages and current operating measurements corresponding to several key nodes in the substation. Evaluation indicators such as voltage exceedance rate, three-phase imbalance, and phase-cutting frequency are calculated based on the actual operating data. Parameters are adaptively adjusted and optimized based on the evaluation results, and the adjusted parameters are applied to subsequent control cycles.

[0102] In this embodiment, the specific process for calculating the voltage over-limit evaluation index is shown in the following formula: ; in, This indicates the voltage over-limit evaluation index within the evaluation window or the current control cycle; Indicates key nodes At parting The voltage value on; and These represent the upper and lower limits of the permissible voltage, respectively. This indicates the amount of voltage exceeding the upper limit; when the voltage does not exceed the upper limit, this item is 0. This indicates the amount exceeding the limit when the voltage is below the lower limit; when the voltage is not below the lower limit, this item is 0. The larger the value, the more severe the voltage limit violation at critical nodes; This indicates that the voltages of all critical nodes are within the allowable range.

[0103] The imbalance index can be the three-phase imbalance index on the load side or the voltage imbalance degree. If the voltage exceeds the limit, the evaluation index... If the voltage remains consistently high, increase the weighting coefficient of the voltage control term in the overall objective function. Alternatively, the weighting of the available reactive power regulation capacity of charging piles could be increased to prioritize ensuring the voltage compliance of key nodes; if frequent switching or increased risk of user complaints occurs, the weighting coefficient of the phase-switching penalty term could be increased. Or increase the minimum cooling interval between two commutations of a single charging pile. Reduce unnecessary phase-switching actions; if the treatment effect is insufficient and the reactive power regulation capacity of all charging piles is saturated, a more conservative charging power limit strategy can be triggered, or an alarm can be sent to the operation and maintenance system. It is recommended to add centralized compensation equipment on the transformer substation side.

[0104] In practical operation, this embodiment addresses the voltage management challenges brought about by the centralized access of electric vehicle charging piles in low-voltage distribution areas. It proposes a power quality management method for distribution areas, centered on the collaborative control of charging pile groups, to address typical power quality issues such as undervoltage at end nodes, localized overvoltage, three-phase load imbalance, and increased neutral current. The key technical challenges to be solved are: to fully explore and utilize the reactive power regulation potential and three-phase load balancing regulation potential of the charging pile grid-connected side, without changing or minimizing changes to the existing power distribution equipment configuration, and to construct a group control calculation and command issuance mechanism that can be implemented at the edge terminal; to ensure that the charging piles do not exceed their rated apparent capacity and current limits while meeting the voltage qualification boundary constraints and three-phase imbalance suppression targets, to control the smoothness of reactive power changes, to limit the phase switching frequency, and to avoid significant impact on the normal charging experience of users; and to ensure the system has operational stability and degradeable operation capabilities under conditions of incomplete distribution area measurements, unstable communication, and highly random electric vehicle charging access behavior, achieving sustainable, assessable, and closed-loop optimization of voltage management effects.

[0105] This embodiment adopts a closed-loop technical solution for low-voltage distribution areas, based on measurement, modeling, joint solution, execution, and evaluation. An approximate voltage model is established based on the distribution area topology and branch parameters of the lines. Alternatively, a multi-phase voltage sensitivity model of the distribution area is obtained through disturbance calculations and online identification methods, assessing the impact of node voltage on active power injection, reactive power injection, and phase load distribution changes. The most sensitive terminal critical node for voltage quality is pre-selected as the core object for evaluating voltage constraints and mitigation effectiveness. Then, with preset constraints such as critical node voltage compliance constraints, three-phase load imbalance suppression, and user charging demand protection as core objectives, while also considering equipment operating costs and system stability, the reactive power setpoint of the charging pile group, phase allocation, and phase switching status are used as joint decision variables. Combined with engineering constraints such as charging pile apparent capacity boundary constraints, reactive power ramp-up constraints, maximum daily commutation times for a single charging pile, minimum interval between two commutations, node voltage constraints, and user charging demand protection constraints, directly executable charging pile reactive power adjustment commands and phase scheduling commands are obtained.

[0106] Finally, the control results obtained from the optimization solution are converted into a command form that the charging pile can recognize. For charging piles that support direct reactive power setting, reactive power commands are issued. For charging piles that only support power factor setting, the commands are converted into corresponding power factor commands and lead / lag indicators. Stability control measures such as command limiting, reactive power ramping limit, voltage dead zone and hysteresis are superimposed on the station control side or the charging pile side. At the same time, a secondary safety check is performed on the phase switching commands. When communication is abnormal or some charging piles are offline, a degraded operation strategy is automatically triggered to ensure the basic safe operation of the system.

[0107] Meanwhile, this embodiment also continuously evaluates the operating indicators of the transformer area based on a sliding time window, including the voltage over-limit rate of key nodes, the three-phase load imbalance, voltage imbalance, neutral current, transformer area loss, and user charging completion rate and phase switching frequency, etc. Based on the evaluation results, the voltage sensitivity model parameters, the weight parameters of the comprehensive optimization objective function, and various control threshold parameters are adaptively updated, thereby realizing continuous closed-loop management of the transformer area's power quality.

[0108] In practical implementation, this embodiment has the following beneficial effects: Compared to the traditional approach of treating charging piles as uncontrollable loads and managing them solely through power grid capacity upgrades or the addition of dedicated compensation devices, this embodiment fully leverages and engineers the reactive power regulation capabilities of the charging pile cluster's grid-connected side. This enables numerous dispersed charging interfaces to provide local voltage support, essentially transforming each charging pile into a distributed, small reactive power compensation unit. Utilizing the rapid adjustment capabilities of its grid-connected power electronic converter, voltage support is achieved locally at the load connection point. This significantly reduces the probability of undervoltage at the end nodes of the distribution area during peak charging load periods, effectively mitigating user charging power fluctuations caused by line voltage drops.

[0109] Compared to the static power factor setting of a single pile or the autonomous droop control mode of a single pile, this embodiment achieves the global unified satisfaction of the reactive power coordinated adjustment of multiple piles and the voltage constraints of key nodes through the group control and collaborative optimization solution at the transformer area level. This effectively avoids problems such as reactive power conflict, reactive power circulation and low governance efficiency caused by independent adjustment of a single pile.

[0110] Compared to single-objective control methods that only target voltage management or three-phase imbalance management, this embodiment takes qualified voltage in the transformer area and three-phase load balance as joint optimization objectives. It performs unified modeling and collaborative optimization calculation of phase allocation, phase switching capability, and reactive power regulation capability. This makes the voltage management effect not only reflected in the improvement of the average voltage level in the transformer area, but also simultaneously achieve comprehensive power quality benefits such as reducing the three-phase voltage difference, reducing the neutral current, and reducing the losses of transformer lines and transformers in the transformer area.

[0111] Compared to theoretical optimization schemes that do not consider actual engineering constraints, this embodiment explicitly introduces engineering constraints such as apparent capacity boundary constraints of charging piles, reactive power ramping constraints, minimum phase switching interval constraints, daily commutation limit constraints, communication anomaly degradation operation constraints, and user charging demand protection constraints into the optimization model. This ensures that the output control strategy has practical feasibility and long-term operational sustainability, effectively reducing the adverse effects of frequent phase switching and reactive power adjustment on the reliability of charging pile equipment and user charging experience.

[0112] Meanwhile, this embodiment provides a hierarchical decomposition solution strategy for edge computing scenarios during the optimization process, decoupling phase optimization and reactive power optimization into two-layer problems with different time scales. This enables large-scale joint optimization problems to be solved and implemented in real time on the edge controller of the transformer substation or the station control side of the charging station. At the same time, through closed-loop evaluation and parameter adaptive update mechanism, the voltage sensitivity model parameters and optimization target weight parameters can be dynamically adjusted according to changes in the operating environment of the transformer substation, load structure and the scale of charging pile access. Thus, under the real-world engineering conditions where electric vehicle charging access has strong randomness and volatility, it can still maintain stable voltage management and three-phase balance effects.

[0113] In summary, this embodiment replaces some dedicated governance resources with charging pile clusters, replaces fragmented single-objective control with joint and collaborative optimization, and ensures the feasibility of the solution with engineering constraints. In high-density electric vehicle charging access scenarios, it effectively improves the voltage quality and three-phase balance of low-voltage distribution areas and effectively reduces the overall governance cost of distribution areas.

[0114] Example 2: This embodiment provides a transformer substation voltage management system based on reactive power and phase balance, including: a voltage approximation module, an imbalance index calculation module, an objective function module, a constraint construction module, a scheme output module, and an instruction output module; wherein: The voltage approximation module is used to construct a voltage approximation model based on the pre-acquired transformer area topology connection relationship, branch parameters and current operating measurements; The imbalance index calculation module is used to obtain the load-side three-phase imbalance index and several heavily loaded phase charging piles based on the transformer area topology connection relationship and current operating measurements. The imbalance index calculation module is also used to obtain several three-phase voltage phasors corresponding to several key nodes in the transformer area, and to obtain the voltage-side three-phase imbalance index based on the several three-phase voltage phasors. The imbalance index calculation module is also used to obtain a three-phase imbalance evaluation index based on the load-side three-phase imbalance index and the voltage-side three-phase imbalance index. The objective function module is used to construct a joint optimization objective function based on the three-phase imbalance evaluation index and preset weight coefficients; The constraint construction module is used to construct target constraint conditions based on the voltage approximation model and preset constraint conditions; The scheme output module is used to obtain a candidate phase-specific scheme set based on a number of heavy-load phase charging piles, and to obtain the phase-specific scheduling result and the target reactive power adjustment amount based on the target constraints, the candidate phase-specific scheme set and the joint optimization objective function; The instruction output module is used to output executable instructions for the charging pile based on the phase scheduling results and the target reactive power adjustment.

[0115] Example 3: Based on the above embodiment of a transformer substation voltage management method based on reactive power and phase balance, this embodiment provides a transformer substation voltage management method based on reactive power and phase balance, the complete execution flow of which is as follows: Figure 2 As shown, the specific steps include: S21. Data Acquisition and Status Construction: After the distribution area voltage management system is started, the first step is to perform data acquisition and distribution area operation status construction: The system pre-acquires the distribution area topology and branch parameters from the distribution system ledger, including the resistance and reactance parameters of each phase of the distribution line; real-time operation measurement data is collected from the low-voltage side outlet of the distribution transformer, the total energy meter of the distribution area, and pre-selected key terminal nodes, including the three-phase voltage, three-phase current, total three-phase active power, total three-phase reactive power, and the phase voltage of each key node; real-time status data of the charging pile group is collected from the charging station control system or each charging pile terminal, including the real-time active charging power of each charging pile, the current available apparent capacity, the upper and lower limits of reactive power regulation, the currently connected phase, whether it has the ability to switch between energized phases, the ability to independently control the three-phase power, and the last phase switching time; and all collected data undergoes time-stamp alignment, outlier removal, missing data completion, and consistency verification to generate a standardized distribution area operation status vector and charging pile group resource capacity vector.

[0116] S22. Distribution Area Operation Status Statistics: Based on the preprocessed data, the three-phase voltage, three-phase current, three-phase power distribution, and real-time charging status of all charging piles in the distribution area are statistically obtained, and the load level and initial power quality status of the current distribution area are identified.

[0117] S23. Constructing an approximate voltage model and sensitivity model for the transformer substation: Based on the substation topology, branch parameters, and current operating measurements, construct a multiphase voltage sensitivity model for the substation, and establish an approximate voltage model based on this. Using the current operating state as the baseline operating point, establish a three-phase power flow model for the substation, and calculate the voltage of each phase at each node under the baseline state; apply small active power disturbances to all nodes in the substation sequentially, keeping the power of other nodes constant, recalculate the node voltages after the disturbances, and calculate the active power voltage sensitivity coefficient; apply small reactive power disturbances to all nodes in the substation sequentially, keeping the power of other nodes constant, recalculate the node voltages after the disturbances, and calculate the reactive power voltage sensitivity coefficient; calculate the equivalent voltage influence coefficient of each charging pile by combining the charging pile node access relationship; construct an approximate voltage model, and establish the mapping relationship between the reactive power regulation of charging piles and the voltage changes of key nodes.

[0118] S24. Construct a joint optimization problem: With key node voltage qualification constraints, three-phase load imbalance suppression and user charging demand protection as the core objectives, while taking into account equipment operating costs and system operation stability, construct a joint optimization objective function and objective constraints.

[0119] S25. Engineering Decomposition Solution for Generating Candidate Phase Allocation Schemes in the Outer Layer: A hierarchical decomposition solution strategy is adopted to reduce computational complexity. First, outer layer phase optimization is performed. Based on the current total active load distribution of the transformer area, heavy-load and light-load phases are identified. Heavy-load phase charging piles that meet the switchability judgment conditions are selected. The judgment conditions include: having the ability to switch phases while energized, not being in the phase switching cooling lockout period, the cumulative number of phase switching times on the day not reaching the upper limit, the real-time charging active power being greater than the preset minimum switching power threshold, and not being set to the prohibited switching mode by the user. According to the principle of prioritizing the phase with the greatest imbalance, a finite number of candidate phase allocation schemes are generated. Each scheme corresponds to different combinations of switching some heavy-load phase charging piles to light-load phases.

[0120] S26. Solving reactive power optimization with fixed phase schemes: For any candidate phase access quantity in the candidate phase scheme set, fix the phase access decision variable, decompose the joint optimization problem into an inner reactive power optimization subproblem, and use the quadratic programming algorithm to solve the subproblem to obtain the optimal candidate reactive power adjustment quantity under the candidate phase scheme.

[0121] S27. Calculate the total cost of the candidate scheme: Based on the solution results of the inner reactive power optimization, calculate the comprehensive total cost of the candidate phase scheme.

[0122] S28. Determine whether all candidate solutions have been traversed: Determine whether all candidate solutions in the candidate solution set have been traversed: If not, return to step S25; if traversal is complete, proceed to step S29.

[0123] S29. Select the scheme with the minimum total cost as the optimal output solution: Compare the total cost of all candidate phase schemes, select the scheme with the minimum total cost as the final optimal output solution, and obtain the corresponding phase scheduling result and target reactive power adjustment amount.

[0124] S210, Convert to charging pile execution command: Convert the optimal solution into an execution command that the charging pile can recognize. For charging piles that support direct reactive power setting, directly issue the target reactive power adjustment amount. For charging piles that only support power factor setting, convert the target reactive power adjustment amount into the corresponding power factor command. At the same time, determine the leading or lagging attribute of the power factor according to the positive or negative sign of the target reactive power adjustment amount. For charging piles that need to perform phase switching, issue the target phase switching command.

[0125] S211. Safety Verification (Voltage Dead Zone, Phase Switching Interval): A second safety verification is performed before the command is issued, including voltage dead zone verification. If the current measured voltage is within the dead zone near the voltage threshold, hysteresis control is superimposed on the reactive power command to avoid voltage fluctuations caused by frequent adjustments. Phase switching interval verification is also included to check whether the charging pile to be executed with the phase switching command meets the minimum phase switching interval constraint and the daily maximum phase switching frequency constraint. If the safety verification fails, proceed to step S212 for command adjustment or rollback; if the verification passes, proceed to step S213.

[0126] S12. Command adjustment or rollback: Adjust commands that fail the safety check; cancel the phase-cutting action and roll back to the reactive power management strategy only for commands that do not meet the phase-cutting constraints; limit the reactive power command that may cause drastic voltage fluctuations and reduce the reactive power regulation range.

[0127] S213. Command issued to charging pile for execution: The control command that has passed the safety verification is issued to the corresponding charging pile or station control device for execution. The charging pile adjusts the reactive power output or performs phase switching operation according to the command.

[0128] S214. Closed-loop evaluation and adaptation: Within the preset sliding evaluation window (typically 15~60 minutes), continuously collect the actual operating data of the transformer area after the command is executed, and calculate evaluation indicators such as voltage over-limit rate, average voltage over-limit amount, average three-phase imbalance, and average phase cutting frequency.

[0129] S215. Determine if parameter update is triggered: Based on the evaluation results, determine whether parameter adaptive update is needed. If the voltage limit evaluation index is consistently too high, increase the weight coefficient of the voltage management item or expand the available reactive power regulation capacity coefficient of the charging pile. If phase switching is frequent or the risk of user complaints increases, increase the weight coefficient of the phase switching penalty item or increase the minimum phase switching interval. If the management effect is insufficient and the reactive power regulation capacity of all charging piles is saturated, trigger a more conservative charging power upper limit strategy or send an alarm to the operation and maintenance system. If parameter update is triggered, return to step S21 and use the updated parameters to enter the next control cycle. If parameter update is not triggered, directly enter the next control cycle and repeat the above steps.

[0130] This embodiment achieves a joint closed-loop management of low-voltage distribution area voltage and three-phase imbalance through the above complete process. It can effectively solve the power quality problems caused by high-density charging access by making full use of the adjustment capabilities of the charging pile group without changing the existing power distribution equipment configuration.

[0131] Example 4: Based on the above embodiment of a transformer substation voltage management method based on reactive power and phase balance, another embodiment of the present invention provides a terminal device, which includes a processor, a memory, and a computer program stored in the memory and configured to be executed by the processor. When the processor executes the computer program, it implements a transformer substation voltage management method based on reactive power and phase balance according to any embodiment of the present invention.

[0132] For example, in this embodiment, the computer program can be divided into one or more modules, which are stored in the memory and executed by the processor to complete the present invention. The one or more modules may be a series of computer program instruction segments capable of performing a specific function, which describe the execution process of the computer program in the terminal device.

[0133] The terminal device may be a desktop computer, laptop, handheld computer, or cloud server, etc. The terminal device may include, but is not limited to, a processor and a memory.

[0134] The processor can be a Central Processing Unit (CPU), or other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. A general-purpose processor can be a microprocessor or any conventional processor. The processor is the control center of the terminal device, connecting all parts of the terminal device via various interfaces and lines.

[0135] Example 5: Based on the above-described method embodiments, another embodiment of the present invention provides a computer-readable storage medium including a stored computer program, wherein, when the computer program is executed, it controls the device where the computer-readable storage medium is located to execute a transformer voltage management method based on reactive power and phase balance as described in any of the above-described method embodiments of the present invention.

[0136] The modules / units integrated in the device / terminal equipment, if implemented as software functional units and sold or used as independent products, can be stored in a computer-readable storage medium. Based on this understanding, all or part of the processes in the above embodiments of the present invention can also be implemented by a computer program instructing related hardware. The computer program can be stored in a computer-readable storage medium, and when executed by a processor, it can implement the steps of the various method embodiments described above. The computer program includes computer program code, which can be in the form of source code, object code, executable files, or certain intermediate forms. The computer-readable medium can include: any entity or device capable of carrying the computer program code, a recording medium, a USB flash drive, a portable hard drive, a magnetic disk, an optical disk, a computer memory, a read-only memory (ROM), a random access memory (RAM), an electrical carrier signal, a telecommunication signal, and a software distribution medium, etc.

[0137] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. A method for managing transformer substation voltage based on reactive power and phase balance, characterized in that, include: A voltage approximation model is constructed based on the pre-acquired transformer area topology, branch parameters, and current operating measurements. Based on the topological connection relationship of the transformer area and the current operation measurement, the load-side three-phase imbalance index and several heavily loaded phase charging piles are obtained. Obtain several three-phase voltage phasors corresponding to several key nodes in the transformer area, and obtain the three-phase unbalance index on the voltage side based on the several three-phase voltage phasors; Three-phase imbalance evaluation index is obtained based on the load-side three-phase imbalance index and the voltage-side three-phase imbalance index; A joint optimization objective function is constructed based on the three-phase imbalance evaluation index and the preset weight coefficients; Target constraints are constructed based on the voltage approximation model and preset constraints. Based on several heavy-load phase charging piles, a candidate phase-specific scheme set is obtained, and based on the target constraints, the candidate phase-specific scheme set, and the joint optimization objective function, the phase-specific scheduling result and the target reactive power adjustment amount are obtained; Based on the phase scheduling results and the target reactive power adjustment, the output can execute instructions for the charging pile.

2. The method for managing transformer substation voltage based on reactive power and phase balance as described in claim 1, characterized in that, The voltage approximation model constructed based on the pre-acquired transformer area topology, branch parameters, and current operating measurements includes: Obtain the topology connection relationship of the transformer area and the branch parameters and current operating measurements; A multiphase voltage sensitivity model for the transformer area is constructed based on the topological connection relationship of the transformer area, branch parameters, and current operating measurements. A voltage approximation model is constructed based on the multiphase voltage sensitivity model of the transformer area.

3. The method for managing transformer substation voltage based on reactive power and phase balance as described in claim 2, characterized in that, The construction of the multiphase voltage sensitivity model for the transformer substation based on the substation topology, branch parameters, and current operating measurements includes: A three-phase power flow model for the transformer area is constructed based on the topological connection relationship of the transformer area, branch parameters, and current operating measurements. Based on the three-phase power flow model of the transformer area, obtain the reference node voltage data; The active power injection change and active voltage sensitivity coefficient are obtained based on the three-phase power flow model of the transformer area and the preset active power disturbance. Based on the three-phase power flow model of the transformer area and the preset reactive power disturbance, the reactive power injection change and reactive power voltage sensitivity coefficient are obtained. A multiphase voltage sensitivity model for the transformer area is constructed based on the changes in active power injection, active voltage sensitivity coefficient, reactive power injection, and reactive voltage sensitivity coefficient.

4. The method for managing transformer substation voltage based on reactive power and phase balance as described in claim 3, characterized in that, The process of obtaining the active power injection change and active power voltage sensitivity coefficient based on the three-phase power flow model of the transformer area and the preset active power disturbance includes: Based on the three-phase power flow model of the transformer area and the preset active power disturbance, active power disturbance is applied to all nodes in the transformer area to obtain the active power disturbance node voltage data. The active power injection change and active power voltage sensitivity coefficient are calculated based on the reference node voltage data, active power disturbance node voltage data, and preset active power disturbance amount.

5. The method for managing transformer substation voltage based on reactive power and phase balance as described in claim 3, characterized in that, The process of obtaining reactive power injection variation and reactive power voltage sensitivity coefficient based on the three-phase power flow model of the transformer area and the preset reactive power disturbance includes: Based on the three-phase power flow model of the transformer area and the preset reactive power disturbance, reactive power disturbance is applied to all nodes in the transformer area to obtain the voltage data of the reactive power disturbance nodes. The reactive power injection change and reactive power voltage sensitivity coefficient are calculated based on the reference node voltage data, reactive power disturbance node voltage data, and preset reactive power disturbance amount.

6. The method for managing transformer substation voltage based on reactive power and phase balance as described in claim 2, characterized in that, The construction of the voltage approximation model based on the multiphase voltage sensitivity model of the transformer area includes: Obtain the charging pile node access data of all charging piles in the transformer area; A reactive power injection variation function is constructed based on phase access decision variables, reactive power decision variables, and charging pile node access data. A voltage approximation model is constructed based on the reactive power injection variation function and the multiphase voltage sensitivity model of the transformer area.

7. The method for managing transformer substation voltage based on reactive power and phase balance as described in claim 1, characterized in that, The load-side three-phase imbalance index and several heavily loaded phase charging piles obtained based on the transformer area topology and current operational measurements include: Select several adjustable charging piles in the transformer substation that meet the preset coordination and control conditions, and obtain several active charging powers and several node access data corresponding to several adjustable charging piles based on the transformer substation topology connection relationship and current operation measurement. Three-phase base load data are obtained based on the current operating measurements. The total active load of the distribution area is obtained based on the three-phase basic load data and several active charging powers. Based on the total active power load of the transformer area, several heavy-load phase charging piles that meet the preset heavy-load phase conditions are selected. The load-side three-phase imbalance index is obtained based on the total active load of the transformer area, the access data of several nodes, and the phase access decision variables.

8. The method for managing transformer substation voltage based on reactive power and phase balance as described in claim 1, characterized in that, The process of acquiring several three-phase voltage phasors corresponding to several key nodes in the transformer area, and obtaining voltage-side three-phase imbalance indices based on these three-phase voltage phasors, includes: Obtain several three-phase voltage phasors corresponding to several key nodes in the transformer area; For any critical node, the negative sequence voltage component and the positive sequence voltage component are calculated based on the three-phase voltage phasors, and the voltage imbalance of the critical node is calculated based on the negative sequence voltage component and the positive sequence voltage component. The voltage-side three-phase imbalance index is obtained based on the voltage imbalance degree corresponding to several key nodes.

9. The method for managing transformer substation voltage based on reactive power and phase balance as described in claim 1, characterized in that, The process of obtaining a candidate phase-specific scheme set based on several heavy-load phase charging piles, and obtaining the phase-specific scheduling result and target reactive power adjustment amount based on the target constraints, the candidate phase-specific scheme set, and the joint optimization objective function, includes: A candidate phase-specific scheme set is obtained based on several of the aforementioned heavy-duty phase charging piles; The reactive power optimization objective function is obtained by performing inner-layer optimization decomposition on the joint optimization objective function; For any candidate phase access quantity in the candidate phase scheme set, the candidate reactive power adjustment quantity is obtained by solving the reactive power decision variable in the reactive power optimization objective function based on the preset reactive power optimization conditions. Based on the candidate reactive power adjustment quantities, target constraints, and preset output conditions corresponding to all candidate phase access quantities in the candidate phase scheme set, the phase access decision variables in the joint optimization objective function are solved to obtain the phase scheduling result. The candidate reactive power adjustment amount corresponding to the phase scheduling result is taken as the target reactive power adjustment amount.

10. A transformer substation voltage management system based on reactive power and phase balance, characterized in that, include: The module comprises a voltage approximation module, an imbalance index calculation module, an objective function module, a constraint construction module, a scheme output module, and an instruction output module; among which: The voltage approximation module is used to construct a voltage approximation model based on the pre-acquired transformer area topology connection relationship, branch parameters and current operating measurements; The imbalance index calculation module is used to obtain the load-side three-phase imbalance index and several heavily loaded phase charging piles based on the transformer area topology connection relationship and current operating measurements. The imbalance index calculation module is also used to obtain several three-phase voltage phasors corresponding to several key nodes in the transformer area, and to obtain the voltage-side three-phase imbalance index based on the several three-phase voltage phasors. The imbalance index calculation module is also used to obtain a three-phase imbalance evaluation index based on the load-side three-phase imbalance index and the voltage-side three-phase imbalance index. The objective function module is used to construct a joint optimization objective function based on the three-phase imbalance evaluation index and preset weight coefficients; The constraint construction module is used to construct target constraint conditions based on the voltage approximation model and preset constraint conditions; The scheme output module is used to obtain a candidate phase-specific scheme set based on a number of heavy-load phase charging piles, and to obtain the phase-specific scheduling result and the target reactive power adjustment amount based on the target constraints, the candidate phase-specific scheme set and the joint optimization objective function; The instruction output module is used to output executable instructions for the charging pile based on the phase scheduling results and the target reactive power adjustment.

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