Power distribution network voltage regulation method and system comprising quick charging pile

Abstract

The invention relates to the technical field of power distribution network voltage regulation, in particular to a voltage regulation method and a voltage regulation system for a power distribution network comprising a quick charging pile for charging an electric vehicle. The method comprises the following steps: S1, constructing a quick charging pile load model; taking a node k in a power distribution network as an example, the node is set to be connected to m quick charging piles in total. In order to accurately describe the load characteristics of the rapid charging pile, different stages of the charging process need to be considered, and a piecewise function is adopted for modeling; the stages are respectively a constant current charging stage and a constant voltage charging stage; s2, establishing a power distribution network voltage regulation optimization model; a power distribution network voltage regulation optimization model is established by taking minimum distribution network voltage deviation and minimum voltage regulation equipment action times as objective functions, and various constraint conditions of a distribution network are considered at the same time. And S3, optimizing a model solving algorithm. And solving the constructed optimization model by adopting a symbiotic organism search algorithm.

Description

Technical Field

[0001] This invention relates to the field of voltage regulation technology for power distribution networks, and in particular to a voltage regulation method and system for power distribution networks that includes fast charging piles for charging electric vehicles. Background Technology

[0002] With increasing global emphasis on environmental protection and sustainable energy development, electric vehicles, as a clean and efficient mode of transportation, are rapidly gaining market share. This growth trend has led to the increasingly widespread application of charging stations, which, due to their significant advantages of high charging power and fast charging speed, can greatly meet the needs of electric vehicle users for quick energy replenishment.

[0003] However, the integration of numerous fast charging stations into the power distribution network presents several significant challenges. During charging, the power demand of these stations fluctuates rapidly and dramatically, leading to voltage fluctuations in the distribution network. Voltage deviations are particularly pronounced when multiple fast charging stations are connected to the same distribution area simultaneously, or when they are used intensively during peak electricity consumption periods. These fluctuations and deviations not only affect the charging efficiency and safety of the fast charging stations themselves but also adversely impact other users in the distribution network. For example, they can cause some electrical equipment with high voltage stability requirements to malfunction, potentially shortening their lifespan and seriously threatening the safe and stable operation of the distribution network. Existing voltage regulation solutions for the distribution network lack consideration for the impact of fast charging stations on the network voltage, rendering them inadequate to address the voltage fluctuations caused by fast charging station integration. Therefore, it is necessary to design a new solution to address the voltage fluctuations caused by fast charging station integration into the distribution network, ensuring voltage stability and power quality. Summary of the Invention

[0004] This invention aims to solve the voltage fluctuation problem caused by fast charging piles being connected to the power distribution network, realize real-time monitoring of the load changes of fast charging piles, quickly and accurately regulate the voltage of the power distribution network, improve the voltage stability and power quality of the power distribution network, and ensure the normal power supply of fast charging piles and other users.

[0005] The purpose of this invention is to address the shortcomings of existing technologies and provide a power distribution network voltage regulation method incorporating fast charging piles. The specific technical solution is as follows:

[0006] Step S1. Construct a fast charging pile load model;

[0007] Node k in the distribution network is connected to m fast charging piles. To accurately describe the load characteristics of the fast charging piles, different stages of the charging process need to be considered, and piecewise functions are used for modeling.

[0008] The aforementioned stages are the constant current charging stage and the constant voltage charging stage;

[0009] Step S2. Establish a voltage regulation optimization model for the distribution network;

[0010] A voltage regulation optimization model for the distribution network is established with the objective function of minimizing the voltage deviation and minimizing the number of times the voltage regulating equipment operates, while also considering various constraints of the distribution network.

[0011] Step S3. Optimize the model solution algorithm.

[0012] The symbiotic organism search algorithm is used to solve the constructed optimization model to achieve voltage regulation in the distribution network. The steps are as follows:

[0013] Step S3.1, initialize the population;

[0014] Step S3.2, Symbiotic Phase;

[0015] Step S3.3, the symbiotic stage;

[0016] Step S3.4, Parasitic stage;

[0017] Step S3.5, determine the termination condition.

[0018] Specifically, step S1. Fast charging pile load model

[0019] Node k in the power distribution network is connected to m fast charging piles. To accurately describe the load characteristics of the fast charging piles, different stages of the charging process need to be considered, and piecewise functions are used for modeling.

[0020] During the constant current and constant voltage charging phases, the total charging power P of the fast charging pile at node k c,k (t) can be expressed as a piecewise function:

[0021]

[0022] In the formula, t cv,j This represents the time point at which the j-th fast charging pile switches from the constant current charging stage to the constant voltage charging stage.

[0023] During the constant current charging phase, the fast charging station uses a constant charging current I. c,j For charging an electric vehicle battery, j = 1, 2, ..., m; battery terminal voltage U c,j (t) varies with charging time t, and its value is related to the battery's state of charge. The charging power P of the j-th fast charging station during the constant current charging phase... c1,j (t) is:

[0024] P c1,j (t)=I c,j U c,j(t)

[0025] Assume the battery open-circuit voltage is U oc,j The internal resistance is R int,j Then the battery terminal voltage U c,j (t) is represented as:

[0026] U c,j (t)=U oc,j (SOC j (t))+I c,j R int,j

[0027] Where, SOC j (t) represents the state of charge (SOC) of the j-th battery at time t, which is related to its initial state of charge (SOC). 0,j Charging current I c,j It is related to the charging time t, and the calculation formula is:

[0028]

[0029] SOC j (t)=SOC 0,j +△SOC j

[0030] In the formula, C rated,j Let U be the rated capacity of the j-th battery. Open-circuit voltage U. oc,j It's about SOC j The nonlinear function is obtained by polynomial fitting through the charging characteristic curve:

[0031] U oc,j (SOC j ) = a 0,j +a 1,j SOC j +…+a i,j SOC j i +…+a n,j SOC j n

[0032] In the formula, a i，j The fitting coefficients represent the total charging power P of all fast charging piles at node k during the constant current charging phase. c1,k (t) is:

[0033]

[0034] During the constant voltage charging phase, when the battery terminal voltage of the electric vehicle at the j-th fast charging station reaches the set constant voltage charging voltage U... c0,j After that, it enters the constant voltage charging stage, where the charging voltage remains constant and the charging current I...c,j (t) decreases as the battery state of charge increases. The charging power P of the j-th fast charging station during the constant voltage charging phase... c2,j (t) is:

[0035] P c2,j (t)=U c0,j I c,j (t)

[0036] Charging current I c,j The relationship between (t) and the battery state of charge is represented by an exponential decay model:

[0037]

[0038] Where, I c0,j k is the initial charging current at the start of constant voltage charging. j SOC is the attenuation coefficient. j (t) represents the state of charge (SOC) of the j-th battery at time t. cv,j This represents the battery's state of charge when entering the constant-voltage charging phase. The total charging power P of all fast-charging stations at node k during the constant-voltage charging phase. c2,k (t) is:

[0039]

[0040] Step S2 includes:

[0041] Let the actual voltage of each node in the distribution network be V. i,real The rated voltage is V i,reated Then the voltage deviation at node i is ΔV i =V i,real -V i,rated N OLTC Let be the number of operations of the on-load tap-changing transformer. The objective function is:

[0042]

[0043] Where ω1 and ω2 are weighting coefficients representing the relative importance of adjusting voltage deviation and the number of times the voltage regulating device operates in the objective function, respectively, ΔV max N OLTC，max These represent the maximum voltage deviation at the node, the maximum number of on-load tap changer operations, T, the total time period for voltage regulation in the distribution network system, and K, all nodes in the distribution network system.

[0044] The constraints include: power flow equation constraints, voltage amplitude constraints, voltage regulation equipment capacity and regulation range constraints, and voltage regulation equipment operation frequency constraints; among which,

[0045] Power flow equation constraints include:

[0046] The active power equation and reactive power equation of node i in the distribution network are as follows:

[0047]

[0048] In the formula, V i 、V j The voltages at nodes i and j are respectively, G ij 、B ij and θ ij These represent the conductance, reactance, and phase angle between nodes i and j, respectively. i,g Q i,g Let P be the active and reactive power generated by node i. i,d Q i,d Let P be the active and reactive power of the normal load at node i. i,l Q i,l Let P be the active and reactive power losses between node i and other nodes, n be the total number of power balancing nodes in the distribution network, and P be the active and reactive power losses between nodes i and other nodes. c,i (t) and Q c,i (t) represents the active and reactive power of the fast charging pile at node i, as follows:

[0049]

[0050]

[0051] In the formula, The power factor angle for fast charging piles.

[0052] Voltage amplitude constraints include:

[0053] The voltage amplitude at each node in the distribution network should be within the allowable range:

[0054] V i,min ≤V i,real ≤V i,max

[0055] In the formula, V i,min and V i,max These are the lower and upper limits of the voltage amplitude at node i, respectively.

[0056] The capacity and adjustment range constraints of the voltage regulating equipment include:

[0057] For a static var compensator, its reactive power compensation capacity Q SVC Should meet:

[0058] Q SVC，min ≤Q SVC ≤Q SVC，max

[0059] In the formula, Q SVC，min and Q SVC，maxThese are the lower and upper limits of reactive power for the static var compensator, respectively.

[0060] The capacity and adjustment range constraints of voltage regulating equipment include: For on-load tap changing transformers, the tap position T should meet the following requirements:

[0061] T OLTC,min ≤T OLTC ≤T OLTC,max

[0062] In the formula, T OLTC,min and T OLTC,max These are the lower and upper limits of the tap position for on-load tap-changing transformers, respectively.

[0063] The constraint on the number of operations of the voltage regulating equipment includes: to avoid frequent operation of the voltage regulating equipment, the number of operations N of the on-load tap-changing transformer is limited. OLTC Restrictions will be imposed:

[0064] N OLTC ≤N OLTC，max

[0065] In the formula, N OLTC，max This represents the maximum number of operations allowed for an on-load tap-changing transformer within a single dispatching cycle.

[0066] S3. Optimization Model Solving Algorithm

[0067] The symbiotic organism search algorithm is used to solve the constructed optimization model. The specific steps are as follows:

[0068] S3.1: Initialize the population

[0069] An initial population X = [x1,...,x2] is formed by randomly generating N individuals. i ,...,x N ], each individual x i This represents a set of voltage regulation schemes, including decision variables such as the reactive power compensation capacity of the static var compensator and the tap position of the on-load tap-changing transformer. Simultaneously, a fitness value f(x) is assigned to each individual. i The fitness value is the value of the objective function f. Furthermore, the number of on-load tap-changing transformer operations corresponding to each individual is initialized.

[0070] Step S3.2, the symbiotic phase includes:

[0071] For each individual x in the population i Randomly select another individual x j (i≠j). The co-occurrence vector M is defined as:

[0072]

[0073] Individual xi and x j Update based on symbiotic relationships:

[0074]

[0075] In the formula, R1 and R2 are random vectors between [0,1], and B1 and B2 are random integers between [1,2].

[0076] Calculate the number of on-load tap-changing transformer operations for the updated individual. Assume x i The tap position of the intermediate-load tap-changing transformer is from Become The action count is then updated as follows:

[0077]

[0078] like Calculate the fitness value of the updated individual. If the new fitness value is better, replace the original individual; otherwise, keep the original individual unchanged.

[0079] Step S3.3, the symbiotic phase, includes:

[0080] For each individual x in the population i Randomly select another individual x j (i≠j). Individual x i Updated based on the symbiotic relationship:

[0081]

[0082] In the formula, R is a random vector between [0,1], and x k It is a randomly selected individual. Similarly, the number of on-load tap-changing transformer operations of the updated individual is calculated. If the number of operations is satisfied and the fitness value is better, the original individual is replaced.

[0083] Step S3.4, the parasitic stage, includes:

[0084] For each individual x in the population i A parasitic vector P is generated, and some elements of this vector are randomly changed to form a new parasitic solution. The number of times the voltage regulator in the parasitic solution operates is calculated. If the number of operations is satisfied and the fitness value is better than that of the individual with the worst fitness value in the population, then the individual with the worst fitness value is replaced.

[0085] Step S3.5, termination condition determination, including:

[0086] Determine if the termination condition is met: either the maximum number of iterations has been reached or the change in the objective function value is less than a certain threshold. If the termination condition is met, the iteration ends and the global optimal solution is output; otherwise, return to step S2 to continue the iteration.

[0087] The present invention includes a voltage regulation system data acquisition module, a data analysis and decision module, and a voltage regulation execution module utilized in the voltage regulation method for power distribution networks with fast charging piles; wherein the data analysis and decision module is electrically connected to the voltage regulation system data acquisition module and the voltage regulation execution module, respectively.

[0088] The voltage regulation system's data acquisition module, data analysis and decision-making module, and voltage regulation execution module are all commercially available products.

[0089] Data acquisition module: Installed at key nodes in fast charging piles and power distribution networks, such as the low-voltage side of transformers and line branch points. It collects real-time operating data such as charging power, current, and voltage from fast charging piles, as well as voltage and current parameters from the power distribution network. The data acquisition module uses high-precision sensors and smart meters to transmit the collected data to the data analysis and decision-making module via wired or wireless communication.

[0090] Data Analysis and Decision Module: Receives data from the data acquisition module and performs real-time analysis and processing. First, it establishes a load model for the fast charging piles; then, combining the real-time operating parameters of the distribution network, it calculates the required voltage regulation amount and method based on the voltage regulation strategy and optimization algorithm, and sends the voltage regulation command to the voltage regulation execution module.

[0091] Voltage regulation execution module: Based on instructions from the data analysis and decision-making module, it executes corresponding voltage regulation operations. The voltage regulation execution module includes a static var compensator (SVC) and an on-load tap-changing transformer. When a voltage deviation is detected, the on-load tap-changing transformer adjusts its tap position as needed. The SVC maintains stable distribution network voltage by rapidly adjusting reactive power.

[0092] This invention has the following characteristics:

[0093] This invention proposes a voltage regulation method and system for distribution networks incorporating fast charging piles. The system integrates a data acquisition module, a data analysis and decision-making module, and a voltage regulation execution module. The data analysis and decision-making module constructs a fast charging pile load model and a distribution network voltage regulation optimization model specifically for distribution networks with fast charging piles. In the proposed method, the fast charging pile load model accurately characterizes the dynamic characteristics of the charging load, and the voltage regulation optimization model is combined with the distribution network voltage regulation optimization model to collaboratively optimize the voltage control strategy. This effectively solves the voltage limit exceeding problem in distribution networks with fast charging piles, significantly improving the safe and stable operation performance of the distribution network. Attached Figure Description

[0094] Figure 1 This is a schematic diagram of the low-voltage regulation system structure of the power distribution network containing fast charging piles in this invention;

[0095] Figure 2 The diagram shows the structure of the computer equipment involved in the power distribution network voltage regulation system.

[0096] Figure 3 This is a schematic diagram of the IEEE 33-node distribution network used in the embodiments of the present invention;

[0097] Figure 4 This is a schematic diagram of the tap position adjustment strategy for the on-load tap-changing transformer in an embodiment of the present invention. Detailed Implementation

[0098] See attached document Figure 1-4 The voltage regulation system for power distribution networks containing fast charging piles proposed in this invention is as follows: Figure 1 As shown, the specific implementation plan is as follows:

[0099] (I) Data Acquisition Module Setup: Installed at key nodes in the fast charging piles and power distribution network, such as the low-voltage side of transformers and line branch points. This module collects real-time charging power, current, voltage, and other operational data from the fast charging piles, as well as voltage and current parameters from the power distribution network. The data acquisition module utilizes high-precision sensors and smart meters, transmitting the collected data to the data analysis and decision-making module via wired or wireless communication.

[0100] (II) Establishing a Data Analysis and Decision-Making Module: This module receives data from the data acquisition module and performs real-time analysis and processing. First, a load model for the fast charging piles is established. Then, combining the real-time operating parameters of the distribution network, and based on the voltage regulation strategy and optimization algorithm, the required voltage regulation amount and method are calculated, and a voltage regulation command is sent to the voltage regulation execution module. Specifically:

[0101] (1) Fast charging pile load model

[0102] Taking node k in the distribution network as an example, we assume that this node is connected to m fast charging piles. To accurately describe the load characteristics of the fast charging piles, we need to consider the different stages of the charging process and use piecewise functions for modeling.

[0103] Constant current charging stage

[0104] During the constant current charging phase, the fast charging station uses a constant current I. c,j (j=1,2,…m) Charge the electric vehicle battery. Battery terminal voltage U c,j (t) varies with charging time t, and its value is related to the battery's state of charge. For the j-th fast charging station, its charging power P during the constant current charging phase is... c1,j (t) is:

[0105] P c1,j (t)=I c,j U c,j (t)

[0106] Assume the battery open-circuit voltage is U oc,j The internal resistance is R int,j Then the battery terminal voltage U c,j (t) can be expressed as:

[0107] U c,j (t)=U oc,j (SOC j (t))+I c,j R int,j

[0108] Where, SOC j (t) represents the state of charge (SOC) of the j-th battery at time t, which is related to its initial state of charge (SOC). 0,j Charging current I c,j It is related to the charging time t, and the calculation formula is:

[0109]

[0110] SOC j (t)=SOC 0,j +△SOC j

[0111] In the formula, C rated,j Let U be the rated capacity of the j-th battery. Open-circuit voltage U. oc,j It's about SOC j The nonlinear function is obtained by polynomial fitting through the charging characteristic curve:

[0112] U oc,j (SOC j ) = a 0,j +a 1,j SOC j +…+a i,j SOC j i +…+a n,j SOC j n

[0113] In the formula, a i，j The fitting coefficients are given. Therefore, the total charging power P of all fast charging stations at node k during the constant current charging phase is... c1,k (t) is:

[0114]

[0115] Constant voltage charging stage

[0116] When the battery terminal voltage of the electric vehicle at the j-th fast charging station reaches the set constant voltage charging voltage U c0,j After that, it enters the constant voltage charging stage, where the charging voltage remains constant and the charging current I... c,j (t) decreases as the battery state of charge increases. The charging power P of the j-th fast charging station during the constant voltage charging phase... c2,j (t) is:

[0117] P c2,j (t)=U c0,j I c,j (t)

[0118] Charging current I c,j The relationship between (t) and the battery state of charge can be represented by an exponential decay model:

[0119]

[0120] Where, I c0,j k is the initial charging current at the start of constant voltage charging. j SOC is the attenuation coefficient. cv,j This represents the battery's state of charge when entering the constant-voltage charging phase. The total charging power P of all fast-charging stations at node k during the constant-voltage charging phase. c2,k (t) is:

[0121]

[0122] In summary, during the constant current and constant voltage charging phases, the total charging power P of the fast charging pile at node k is... c,k (t) can be expressed as a piecewise function:

[0123]

[0124] In the formula, t cv,j This represents the time point at which the j-th fast charging pile switches from the constant current charging stage to the constant voltage charging stage.

[0125] (2) Distribution Network Voltage Regulation Optimization Model

[0126] A voltage regulation optimization model is established with the objective function of minimizing the distribution network voltage deviation and minimizing the number of times the voltage regulating equipment operates, while also considering various constraints of the distribution network.

[0127] objective function

[0128] Let the actual voltage of each node in the distribution network be V. i,real The rated voltage is V i,reated Then the voltage deviation at node i is ΔV i =V i,real -V i,rated NOLTC Let be the number of operations of the on-load tap-changing transformer. The objective function is:

[0129]

[0130] Where ω1 and ω2 are weighting coefficients used to adjust the relative importance of voltage deviation and the number of times the voltage regulating device operates in the objective function, ΔV max N OLTC，max These are the maximum voltage deviation at the node and the maximum number of operations of the on-load tap-changing transformer, respectively.

[0131] Constraints

[0132] Power flow equation constraints

[0133] Active power equations and reactive power equations of node i in the distribution network

[0134]

[0135] In the formula, V i 、V j The voltages at nodes i and j are respectively, G ij 、B ij and θ ij These represent the conductance, reactance, and phase angle between nodes i and j, respectively. i,g Q i,g Let P be the active and reactive power generated by node i. i,d Q i,d Let P be the active and reactive power of the normal load at node i. i,l Q i,l P represents the active and reactive power losses of the line between node i and other nodes. c,i (t) and Q c,i (t) represents the active and reactive power of the fast charging pile at node i, i.e.,

[0136]

[0137] In the formula, The power factor angle for fast charging piles.

[0138] Voltage amplitude constraint

[0139] The voltage amplitude at each node in the distribution network should be within the allowable range:

[0140] V i,min ≤V i,real ≤V i,max

[0141] In the formula, V i,min and V i,max These are the lower and upper limits of the voltage amplitude at node i, respectively.

[0142] Constraints on the capacity and adjustment range of voltage regulating equipment

[0143] For a static var compensator, its reactive power compensation capacity Q SVC Should meet:

[0144] Q SVC，min ≤Q SVC ≤Q SVC，max

[0145] In the formula, Q SVC，min and Q SVC，max These are the lower and upper limits of reactive power for the static var compensator, respectively.

[0146] For on-load tap-changing transformers, the tap position T should meet the following requirements:

[0147] T OLTC,min ≤T OLTC ≤T OLTC,max

[0148] In the formula, T OLTC,min and T OLTC,max These are the lower and upper limits of the tap position for on-load tap-changing transformers, respectively.

[0149] Constraints on the number of times a voltage regulating device can operate

[0150] To avoid frequent operation of the voltage regulating equipment, the number of its operations needs to be limited:

[0151] N OLTC ≤N OLTC，max

[0152] In the formula, N OLTC，max This represents the maximum number of operations allowed for an on-load tap-changing transformer within a single dispatching cycle.

[0153] (3) Optimize the model solution algorithm

[0154] The symbiotic organism search algorithm is used to solve the constructed optimization model. The specific steps are as follows:

[0155] Step S1, initialize the population, including:

[0156] An initial population X = [x1,...,x2] is formed by randomly generating N individuals. i ,...,x N ], each individual x i This represents a set of voltage regulation schemes, including decision variables such as the reactive power compensation capacity of the static var compensator and the tap position of the on-load tap-changing transformer. Simultaneously, a fitness value f(x) is assigned to each individual. iThe fitness value is the value of the objective function Z. Furthermore, the number of on-load tap-changing transformer operations corresponding to each individual is initialized.

[0157] Step S2, the symbiotic phase, includes:

[0158] For each individual x in the population i Randomly select another individual x j (i≠j). The co-occurrence vector M is defined as:

[0159]

[0160] Individual x i and x j Update based on symbiotic relationships:

[0161]

[0162] In the formula, R1 and R2 are random vectors between [0,1], and B1 and B2 are random integers between [1,2].

[0163] Calculate the number of on-load tap-changing transformer operations for the updated individual. Assume x i The tap position of the intermediate-load tap-changing transformer is from Become The action count is then updated as follows:

[0164]

[0165] like Calculate the fitness value of the updated individual. If the new fitness value is better, replace the original individual; otherwise, keep the original individual unchanged.

[0166] Step S3, the symbiotic phase, includes:

[0167] For each individual x in the population i Randomly select another individual x j (i≠j). Individual x i Updated based on the symbiotic relationship:

[0168]

[0169] In the formula, R is a random vector between [0,1], and x k It is a randomly selected individual. Similarly, the number of operations of the static var compensator and on-load tap changer of the updated individual is calculated. If the number of operations is satisfied and the fitness value is better, the original individual is replaced.

[0170] Step S4, the parasitic stage, includes:

[0171] For each individual x in the population i A parasitic vector P is generated, and some elements of this vector are randomly changed to form a new parasitic solution. The number of times the voltage regulator of the parasitic solution operates is calculated. If the number of operations is satisfied and the fitness value is better than that of the individual with the worst fitness value in the population, then that individual is replaced.

[0172] Step S5, termination condition determination, including:

[0173] Determine if the termination condition is met, typically by reaching the maximum number of iterations or the change in the objective function value being less than a certain threshold. If the termination condition is met, the iteration ends and the global optimal solution is output; otherwise, return to step 2 to continue iterating.

[0174] (III) Setting up the voltage regulation execution module: Based on the instructions from the data analysis and decision-making module, the module executes corresponding voltage regulation operations. The voltage regulation execution module includes a static var compensator (SVC) and an on-load tap-changing transformer (OTCT). When a voltage deviation is detected, the OOTCT adjusts the tap position as needed, and the SVC maintains stable distribution network voltage by rapidly adjusting reactive power.

[0175] Table 1 Comparison of voltage control effects of different algorithms

[0176]

[0177] Based on the above implementation scheme, in order to verify the beneficial effects of the present invention, a specific calculation example is used for analysis. Figure 2 The IEEE 33-node distribution network shown is analyzed. The rated voltage of the distribution network is 12.66kV, and the allowable range of node voltage is ±5% of the rated voltage. Four fast charging piles are connected at nodes 9, 14, 21, and 30, with a rated power of 120kW and a rated capacity of 60kWh.

[0178] Figure 4 The figure shows the tap position adjustment strategy of the on-load tap-changing transformer after optimization by the method proposed in this patent. As can be seen from the figure, the tap position of the on-load tap-changing transformer was adjusted a total of 11 times to cope with voltage fluctuations.

[0179] As shown in Table 1, the proposed method can effectively mitigate voltage fluctuations, thereby better suppressing voltage dips and fluctuations under the load impact of fast charging piles and ensuring the reliability of the distribution network operation. Through implementation example analysis, it is evident that the low-voltage regulation method for distribution networks proposed in this invention can effectively reduce voltage fluctuations in areas containing fast charging piles, and plays a positive role in improving the safe operation performance of the distribution network.

Claims

1. A voltage regulation method for a power distribution network including fast charging piles, characterized in that, include: Step S1: Construct a fast charging pile load model; The different stages of the charging process are the constant current charging stage and the constant voltage charging stage. Step S2: Establish a voltage regulation optimization model for the distribution network; A distribution network voltage regulation optimization model is established with the objective function of minimizing the distribution network voltage deviation and minimizing the number of voltage regulation equipment operations, while also considering various constraints of the distribution network. Step S3: Optimize the model solution algorithm; The symbiotic organism search algorithm is used to solve the constructed optimization model to achieve voltage regulation in the distribution network. The steps are as follows: Step S3.1, initialize the population; Step S3.2, Symbiotic Phase; Step S3.3, the symbiotic stage; Step S3.4, Parasitic stage; Step S3.5, determine the termination condition.

2. The voltage regulation method for a power distribution network including a fast charging pile according to claim 1, characterized in that: In step S1, node k in the distribution network is connected to a total of m fast charging piles; a piecewise function is used for modeling. During the constant current and constant voltage charging phases, the total charging power P of the fast charging pile at node k c,k (t) is represented as a piecewise function: In the formula, t cv,j This represents the time point at which the j-th fast charging pile switches from the constant current charging stage to the constant voltage charging stage.

3. A voltage regulation method for a power distribution network including a fast charging pile according to claim 2, characterized in that: During the constant current charging phase, the fast charging station uses a constant charging current I. c,j For charging an electric vehicle battery, j = 1, 2, ..., m; battery terminal voltage U c,j (t) varies with charging time t, and its value is related to the battery's state of charge; the charging power P of the j-th fast charging pile during the constant current charging stage. c1,j (t) is: P c1,j (t)=I c,j U c,j (t) Assume the battery open-circuit voltage is U oc,j The internal resistance is R int,j Then the battery terminal voltage U c,j (t) is represented as: U c,j (t)=U oc,j (SOC j (t))+I c,j R int,j Where, SOC j (t) represents the state of charge (SOC) of the j-th battery at time t, which is related to its initial state of charge (SOC). 0,j Charging current I c,j It is related to the charging time t, and the calculation formula is: SOC j (t)=SOC 0,j +△SOC j In the formula, C rated,j The rated capacity of the j-th battery; the open-circuit voltage U oc,j It's about SOC j The nonlinear function is obtained by fitting an nth-order polynomial to the charging characteristic curve: U oc,j (SOC j )=a 0,j +a 1,j SOC j +…+a i,j SOC j i +…+a n,j SOC j n In the formula, a i，j The fitting coefficients represent the total charging power P of all fast charging stations at node k during the constant current charging phase. c1,k (t) is:

4. A power distribution network voltage regulation method incorporating fast charging piles according to claim 2, characterized in that: During the constant voltage charging phase, when the battery terminal voltage of the electric vehicle at the j-th fast charging station reaches the set constant voltage charging voltage U... c0,j After that, it enters the constant voltage charging stage, where the charging voltage remains constant and the charging current I... c,j (t) decreases as the battery state of charge increases; the charging power P of the j-th fast charging pile during the constant voltage charging phase c2,j (t) is: P c2,j (t)=U c0,j I c,j (t) Charging current I c,j The relationship between (t) and the battery state of charge is represented by an exponential decay model: Where, I c0,j k is the initial charging current at the start of constant voltage charging. j SOC is the attenuation coefficient. j (t) represents the state of charge (SOC) of the j-th battery at time t. cv,j The state of charge of the battery when entering the constant voltage charging stage; the total charging power P of all fast charging piles at node k during the constant voltage charging stage. c2,k (t) is:

5. A voltage regulation method for a power distribution network including a fast charging pile according to claim 1, characterized in that: Step S2 includes: Let the actual voltage of each node in the distribution network be V. i,real The rated voltage is V i,reated Then the voltage deviation at node i is ΔV i =V i,real -V i,rated N OLTC Let the number of operations of the on-load tap-changing transformer be denoted by the objective function: Where ω1 and ω2 are weighting coefficients representing the relative importance of adjusting voltage deviation and the number of times the voltage regulating device operates in the objective function, respectively, ΔV max N OLTC，max These represent the maximum voltage deviation at the node, the maximum number of on-load tap changer operations, T, the total time period for voltage regulation in the distribution network system, and K, all nodes in the distribution network system.

6. A voltage regulation method for a power distribution network including a fast charging pile according to claim 5, characterized in that: The constraints include: power flow equation constraints, voltage amplitude constraints, voltage regulation equipment capacity and regulation range constraints, and voltage regulation equipment operation frequency constraints; among which, The power flow equation constraints include the active power equation and reactive power equation of node i in the distribution network, as follows: In the formula, V i 、V j The voltages at nodes i and j are respectively, G ij 、B ij and θ ij These represent the conductance, reactance, and phase angle between nodes i and j, respectively. i,g , Q i,g Let P be the active and reactive power generated by node i. i,d , Q i,d Let P be the active and reactive power of the normal load at node i. i,l , Q i,l Let P be the active and reactive power losses between node i and other nodes, n be the total number of power balancing nodes in the distribution network, and P be the active and reactive power losses between nodes i and other nodes. c,i (t) and Q c,i (t) represents the active and reactive power of the fast charging pile at node i, as follows: In the formula, Power factor angle for fast charging piles; Voltage amplitude constraints include: the voltage amplitude at each node in the distribution network should be within the allowable range. In i,min ≤V i,real ≤V i,max In the formula, V i,min and V i,max These are the lower and upper limits of the voltage amplitude at node i, respectively; The capacity and adjustment range constraints of voltage regulating equipment include: for static var compensators, their reactive power compensation capacity Q. SVC Should meet: Q SVC，min ≤Q SVC ≤Q SVC，max In the formula, Q SVC，min and Q SVC，max These are the lower and upper limits of reactive power for the static var compensator, respectively. The capacity and adjustment range constraints of voltage regulating equipment include: For on-load tap changing transformers, the tap position T should meet the following requirements: T OLTC,min ≤T OLTC ≤T OLTC,max In the formula, T OLTC,min and T OLTC,max These are the lower and upper limits of the tap position for on-load tap-changing transformers, respectively. The constraint on the number of operations of the voltage regulating equipment includes: the number of operations N for the on-load tap-changing transformer. OLTC Restrictions will be imposed: N OLTC ≤N OLTC，max In the formula, N OLTC，max This represents the maximum number of operations allowed for an on-load tap-changing transformer within a single dispatching cycle.

7. A power distribution network voltage regulation method incorporating fast charging piles according to claim 1, characterized in that: Step S3.1, initialize the population, including: An initial population X = [x1,...,x2] is formed by randomly generating N individuals. i ,...,x N ], each individual x i This represents a set of voltage regulation schemes, including decision variables such as the reactive power compensation capacity of the static var compensator and the tap position of the on-load tap-changing transformer; simultaneously, a fitness value f(x) is assigned to each individual. i The fitness value is the value of the objective function f; in addition, the number of on-load tap-changing transformer operations corresponding to each individual is initialized.

8. A voltage regulation method for a power distribution network including a fast charging pile according to claim 7, characterized in that: Step S3.2, the symbiotic phase, includes: For each individual x in the population i Randomly select another individual x j , i≠j; the co-occurrence vector M is defined as: Individual x i and x j Update based on symbiotic relationships: In the formula, R1 and R2 are random vectors between [0,1], and B1 and B2 are random integers between [1,2]. Calculate the number of on-load tap-changing transformer operations for each individual after the update; assume x i The tap position of the intermediate-load tap-changing transformer is from Become The action count is then updated as follows: like Calculate the fitness value of the updated individual. If the new fitness value is better, replace the original individual; otherwise, keep the original individual unchanged.

9. A voltage regulation method for a power distribution network including a fast charging pile according to claim 8, characterized in that: Step S3.3, the symbiotic phase, includes: For each individual x in the population i Randomly select another individual x j , i≠j; individual x i Updated based on the symbiotic relationship: In the formula, R is a random vector between [0,1], and x k It is a randomly selected individual; similarly, the number of on-load tap-changing transformer operations of the updated individual is calculated. If the number of operations is satisfied and the fitness value is better, the original individual is replaced.

10. A voltage regulation method for a power distribution network including a fast charging pile according to claim 9, characterized in that: Step S3.4, the parasitic stage, includes: For each individual x in the population i Generate a parasitic vector P, and randomly change some elements of the vector to form a new parasitic solution; calculate the number of times the voltage regulator of the parasitic solution operates. If the number of operations is satisfied and the fitness value is better than the individual with the worst fitness value in the population, then replace the individual with the worst fitness value.

11. A voltage regulation method for a power distribution network including a fast charging pile according to claim 10, characterized in that: Step S3.5, termination condition determination, including: Determine if the termination condition is met, which is either reaching the maximum number of iterations or the change in the objective function value is less than a certain threshold. If the termination condition is met, the iteration ends and the global optimal solution is output; otherwise, return to step S2 to continue iterating.

12. A voltage regulating system, characterized in that: The system includes a voltage regulation system data acquisition module, a data analysis and decision-making module, and a voltage regulation execution module; wherein the data analysis and decision-making module is electrically connected to the voltage regulation system data acquisition module and the voltage regulation execution module respectively; the voltage regulation system is capable of executing the power distribution network voltage regulation method including fast charging piles as described in any one of claims 1-11.

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