Transmission and distribution collaborative energy storage locating and sizing method based on Eartin acceleration method

Abstract

The invention provides a transmission and distribution collaborative energy storage locating and sizing method based on an Eartin acceleration method, and relates to the technical field of power grids, and the method comprises the steps: S1, carrying out the processing of a hub node voltage and a hub node phase angle, and obtaining the installation position and the installation capacity of power distribution network energy storage; s2, performing power distribution network load flow calculation and hub node load flow calculation on the installation position and the installation capacity to obtain hub node capacity; s3, obtaining a corrected hub node capacity through an Ehmite acceleration method; s4, performing power transmission network load flow calculation and hub node load flow calculation on the corrected hub node capacity to obtain a corrected hub node voltage and a corrected hub node phase angle; s5, updating the hub node voltage and the hub node phase angle through an Ehmite acceleration method; s6, repeating the steps S1 to S5 until the hub node voltage and the hub node phase angle meet the error threshold at the same time; the optimal energy storage installation position and capacity are determined from the overall perspective of the power transmission network and the power distribution network, and optimal energy storage configuration is achieved.

Description

Technical Field

[0001] The present invention relates to the field of power grid technology, and in particular to a method for selecting a location and determining a capacity of transmission and distribution coordinated energy storage based on the Aitkin acceleration method. Background Art

[0002] In the context of high penetration of renewable energy access to the grid, the problem of wind and solar power abandonment at the transmission network level is prominent, and power quality problems such as voltage over-limit at the distribution network level are also becoming increasingly prominent. Energy storage has become an effective means of addressing the problem of renewable energy access by enhancing the system's regulation capabilities due to its characteristics such as bidirectional transmission and fast response speed. On the transmission network side, the existing technology "Configuration scheme and economic analysis of energy storage systems participating in peak regulation" adopts a two-layer optimization method to propose a configuration scheme for energy storage to assist grid peak regulation. The inner layer dispatches the system with the goal of minimizing peak regulation costs, and the outer layer iteratively optimizes the configuration of energy storage capacity; the existing technology "Method for site selection and sizing of grid-type converters to improve the stability of new energy power systems" studies the optimization method of site selection and sizing of energy storage systems based on grid-type converters from the perspective of improving system stability margin. On the distribution network side, as more and more distributed power sources are connected to the distribution system, feeder voltage rise is the most significant problem caused by the access of distributed power sources. The energy storage system can effectively improve the voltage over-limit caused by the grid connection of distributed power sources. When the distributed power source output is large, the energy storage system can absorb the electric energy that the load cannot consume, improve the system power stability, and reduce the node overvoltage caused by the power injected by the distributed power source. The prior art "Study on the Impact of User-side Distributed Energy Storage Access on the Distribution Network" proposes an improved particle swarm algorithm to reduce node voltage fluctuations to determine the optimal configuration capacity of energy storage. The prior art "Distribution Network Energy Storage Site Selection and Capacity Determination Based on Improved Multi-objective Particle Swarm Algorithm" proposes the multi-objective optimization problem of distributed energy storage access to the distribution network considering voltage over-limit, and uses an intelligent optimization algorithm to optimize the access location and capacity of distributed energy storage in the distribution network.

[0003] In summary, in the existing energy storage site selection and sizing research, the transmission network and the distribution network are separated and conducted independently. The general method is to treat the distribution network as a typical load node when conducting the transmission network side research, and to treat the transmission network as a balance node when conducting the distribution network side research. However, in the design, although the transmission network and the distribution network belong to different dispatching departments, they are an interconnected whole in operation and exchange power in real time; moreover, the transmission network nodes connected to the distribution network are not always equivalent to balance nodes. Therefore, it is necessary to coordinate the transmission network and the distribution network in the energy storage site selection and sizing research, and optimize them from a global perspective. In addition, for the optimization of energy storage on the distribution network side, whether it is iterative optimization or heuristic algorithm, it is impossible to obtain the analytical expression of voltage and energy storage. For simple systems, it is necessary to rely on a large number of repeated calculations to obtain ideal results; for complex systems, on the one hand, the algorithm is highly dependent, and on the other hand, it faces the dilemma of falling into local optimality.

[0004] In view of this, the present invention proposes a method for selecting and sizing the location of transmission and distribution coordinated energy storage based on the Aitkin acceleration method. First, from the perspective of voltage over-limit, a linear analytical expression of voltage and capacity is derived on the distribution network side. According to the voltage over-limit situation of the system node, the installation location of the energy storage can be quickly determined, and the line loss and voltage regulation requirements can be taken into account to accurately calculate the configured energy storage capacity; secondly, in combination with the grid topology and actual operating parameters, real-time Newton-Raphson power flow calculations are performed on the transmission network and distribution network to avoid the deviation caused by artificially equating the transmission network to a balancing node. In the power flow calculation process, the Aitkin acceleration method is used to accelerate the transmission network side and the distribution network side in parallel to improve the slow convergence speed caused by the large scale of the system. The convergence times of the present invention are within 20 times, and the voltage management error is less than 10 -4 , meeting engineering requirements. Summary of the invention

[0005] The object of the present invention is to provide a method for selecting a site and determining the capacity of transmission and distribution coordinated energy storage based on the Aitkin acceleration method, comprising: S1 processing the hub node voltage and the hub node phase angle to obtain the installation position and installation capacity of the distribution network energy storage; S2 performing distribution network flow calculation and hub node flow calculation on the installation position and the installation capacity to obtain the hub node capacity; S3 correcting the hub node capacity by the Aitkin acceleration method to obtain a corrected hub node capacity; S4 performing transmission network flow calculation and hub node flow calculation on the corrected hub node capacity to obtain a corrected hub node voltage and a corrected hub node phase angle; S5 processing the corrected hub node voltage and the corrected hub node phase angle by the Aitkin acceleration method to update the hub node voltage and the hub node phase angle; S6 repeating S1-S5 until the hub node voltage and the hub node phase angle simultaneously meet the error threshold.

[0006] Furthermore, the installation position of the energy storage in the distribution network is obtained, including: determining the pre-access voltage of each node in the distribution network; determining the post-access voltage of each node after the energy storage is connected to the distribution network; taking the difference between the pre-access voltage and the post-access voltage as the node voltage difference, and determining the node total resistance and node total reactance from each node to the balancing node; determining the power sensitivity coefficient of each node according to the ratio of the node total resistance and the node total reactance to the voltage of the balancing node; the power sensitivity coefficient includes an active power sensitivity coefficient and a reactive power sensitivity coefficient; determining the installation position according to the power sensitivity coefficient, including: for a single-node voltage over-limit, taking the over-limit node as the installation position of the energy storage; for multiple-node voltage over-limit, taking the over-limit node farthest from the balancing node as the installation position of the energy storage.

[0007] Furthermore, the expression of the node voltage difference is:

[0008]

[0009] In the formula, ΔU k represents the node voltage difference between node k before and after energy storage is connected; R k,i and X k,i They represent the total node resistance and total node reactance from the balancing node to node i, R k,1 and X k,1 They represent the resistance and reactance from the balancing node to node 1, R k,N and X k,N They represent the resistance and reactance from the balancing node to the node N respectively; P ESS,i and Q ESS,i Respectively represent the active power and reactive power of energy storage at node i, P ESS,1 and Q ESS,1 They represent the active power and reactive power of energy storage at node 1, respectively, P ESS,N and Q ESS,N Respectively represent the active power and reactive power of energy storage at node N; P LOSS,ESS,i and Q LOSS,ESS,i They represent the active power loss and reactive power loss of energy storage at node i, respectively, P LOSS,ES,1 and Q LOSS,ESS,1 They represent the active power loss and reactive power loss of energy storage at node 1, respectively, P LOSS,ESS,N and Q LOSS,ESS,N They represent the active power loss and reactive power loss of energy storage at node N respectively;

[0010] The expressions of the total resistance of the node and the total reactance of the node are:

[0011] when i <k,

[0012] When i ≥ k,

[0013] In the formula, j represents the second node variable; k represents the third node variable; i represents the first node variable; R k,i and X k,i They represent the total node resistance and total node reactance from the balancing node to node i respectively; r j and x j They represent the inter-node resistance and inter-node reactance of the inter-node lines respectively.

[0014] Furthermore, when there are three out-of-limit nodes, l, h and c, the expression of the installed capacity of the distribution network energy storage is obtained as follows:

[0015]

[0016] Where P ESS and Q ESS Respectively represent the active power and reactive power of the energy storage installation; max represents the maximum value; P ESS,l and Q ESS,l They represent the active power and reactive power of the node numbered l respectively; P ESS,h and Q ESS,h They represent the active power and reactive power of the node numbered h respectively; P ESS,c and Q ESS,c They represent the active power and reactive power of the node numbered c respectively; st represents the constraint condition; ΔU u Indicates the voltage difference that needs to be reduced for the voltage at the over-limit node u to change from the over-limit value to the maximum normal value; U u Indicates the voltage over-limit value at the over-limit node u, u represents the node variable of the over-limit node, and its value is l, h or c; U max Indicates the maximum normal value of the voltage when the node is running; ΔU l , ΔU h and ΔU c Respectively represent the voltage difference that needs to be reduced for the voltage at nodes l, h and c to change from the over-limit value to the normal value; R k,l and X k,l They represent the total node resistance and total node reactance from node k to node l respectively; R k,h and X k,h They represent the total node resistance and total node reactance from node k to node h respectively; R k,c and X k,c They represent the total node resistance and total node reactance from node k to node c respectively.

[0017] Furthermore, the expressions of active power and reactive power of energy storage at the node are:

[0018]

[0019] The expressions of active power loss and reactive power loss of energy storage at the node are:

[0020]

[0021] Where P ESS,i and Q ESS,i represent the active power and reactive power of energy storage at node i respectively; represents the voltage parameter of node j, which is the average value of the voltage of node j before and after energy storage is connected; ΔU k represents the node voltage difference between node k before and after energy storage is connected; j represents the second node variable; k represents the third node variable; i represents the first node variable; r j and x j They represent the inter-node resistance and inter-node reactance of the inter-node line respectively; P LOSS,ESS,i and Q LOSS,ESS,i They represent the active power loss and reactive power loss of the energy storage at node i respectively.

[0022] Furthermore, the expression for modifying the hub node capacity is:

[0023]

[0024] Among them, S' B,k+1 represents the modified hub node capacity; S B,k represents the initial hub node capacity; S B,k+1 represents the capacity of the first hub node; S B,k+1 Represents the capacity of the second hub node.

[0025] Furthermore, the expression for updating the hub node voltage is:

[0026]

[0027] The expression for updating the phase angle of the pivot node is:

[0028]

[0029] In the formula, I' B,k+1 and θ' B,k+1 Respectively represent the updated hub node voltage and hub node phase angle; U B,k and θ B,k Respectively represent the first hub node voltage and the first hub node phase angle; U B,k+1 and θ B,k+1 Respectively represent the second hub node voltage and the second hub node phase angle; U B,k+2 and θ B,k+2represent the modified hub node voltage and the modified hub node phase angle respectively.

[0030] Furthermore, obtaining the hub node voltage, the hub node phase angle and the hub node capacity also includes: S11 obtaining the initial installation position and initial installation capacity of the distribution network energy storage according to the initial hub node voltage and the initial hub node phase angle; S12 performing distribution network flow calculation and hub node flow calculation on the initial installation position and the initial installation capacity to obtain the initial hub node capacity; S13 performing transmission network flow calculation and hub node flow calculation on the initial hub node capacity to obtain the first hub node voltage and the first hub node phase angle; S14 using the first hub node voltage as the initial hub node voltage, and using the first hub node phase angle as the initial hub node phase angle, and repeating S11-S13 until multiple hub node capacities, multiple hub node voltages and multiple hub node phase angles are obtained; the multiple hub node capacities include at least the initial hub node capacity, the first hub node capacity and the second hub node capacity; the multiple hub node voltages include at least the first hub node voltage and the second hub node voltage; the multiple hub node phase angles include at least the first hub node phase angle and the second hub node phase angle.

[0031] Furthermore, the expressions for the power flow calculation of the transmission network, the power flow calculation of the distribution network and the power flow calculation of the hub node are:

[0032]

[0033] In the formula, T represents the transmission network; D represents the distribution network; B represents the hub node; F T (U T , S B , U B ,θ B )=0 means power flow calculation of transmission network; F D (U D , S B , U B ,θ B ) represents the distribution network power flow calculation; F B (U B ,θ B )=0 means hub node power flow calculation; U T Represents the voltage of the transmission network; S B represents the hub node capacity; U B represents the hub node voltage; θ B represents the phase angle of the hub node; U D Indicates the distribution network voltage.

[0034] Furthermore, it also includes optimizing the voltage of the first hub node and the phase angle of the first hub node through a global model for optimizing the location and capacity of transmission and distribution coordinated energy storage; the expression of the global objective function of the global model for optimizing the location and capacity of transmission and distribution coordinated energy storage is:

[0035]

[0036] Where, f represents the global objective function of the global model for optimizing the location and capacity of transmission and distribution coordinated energy storage; max(*) represents the maximum value; min(*) represents the minimum value; represents the renewable energy capacity connected to the transmission grid; represents the renewable energy capacity connected to the distribution network, S ESS Indicates the energy storage configuration capacity of the system;

[0037] The expression of the transmission network side objective function of the global objective function is:

[0038]

[0039] In the formula, f 1 represents the objective function of the transmission network side in the global model of transmission and distribution coordinated energy storage site selection and capacity optimization; t represents the time of power flow calculation; ∑ t (*) indicates the sum of all tidal current moments; represents the renewable energy capacity connected to the transmission grid at time t; represents the renewable energy capacity connected to the distribution network at time t;

[0040] The constraints on the transmission grid side include:

[0041] Power balance constraints on the transmission grid side:

[0042]

[0043] In the formula, and They represent the active power and reactive power generated by the generator connected to the transmission network at time t respectively; and They represent the active power and reactive power generated by the renewable energy power station connected to the transmission grid at time t respectively; and They represent the active and reactive power of the load on the transmission grid side at time t respectively; P B,t and Q B,t They represent the node active power and node reactive power of the hub node at time t respectively; j represents the second node variable; i represents the first node variable; U i represents the node voltage at node i; U j represents the node voltage at node j; G ij and Bij Respectively represent the conductance and susceptance of the branch between node i and node j; θ ij represents the node phase angle of the branch between node i and node j; cos represents the cosine function; sin represents the sine function;

[0044] Active power output constraints and reactive power output constraints of generators on the transmission grid side:

[0045]

[0046] In the formula, and Respectively represent the upper limit and lower limit of the motor active power; and Respectively represent the upper and lower limits of reactive power of the generator;

[0047] Active and reactive output constraints of renewable energy on the transmission grid side

[0048]

[0049] In the formula, and They represent the upper and lower limits of active power of renewable energy power stations in the transmission network respectively; and They represent the upper and lower reactive power limits of the renewable energy power station in the transmission network respectively;

[0050] Transmission grid side node voltage constraints:

[0051]

[0052] In the formula, and They represent the upper and lower limits of the voltage amplitude of the transmission network respectively;

[0053] Thermal stability constraints of transmission line on the grid side:

[0054]

[0055] In the formula, represents the line apparent power of the branch between node i and node j in the transmission network; and They represent the upper and lower limits of apparent power of the lines in the transmission network respectively;

[0056] The expression of the distribution network side objective function of the global objective function is:

[0057] f 2 =minS ESS ;

[0058] The constraints on the distribution network side include:

[0059] Power balance constraints on the distribution network side:

[0060]

[0061] Where, t represents the time of power flow calculation; P B,t and Q B,t Respectively represent the active power and reactive power of the hub node; and They represent the active power and reactive power generated by the distributed renewable energy sources connected to the distribution network respectively; and They represent the active and reactive power of the load on the distribution network side respectively; and They represent the active and reactive power of the energy storage device connected to the distribution network side; U i represents the node voltage at node i; U j represents the node voltage at node j; G ij and B ij Respectively represent the conductance and susceptance of the branch between node i and node j; θ ij represents the node phase angle of the branch between node i and node j; cos represents the cosine function; sin represents the sine function;

[0062] Active and reactive output constraints of distributed renewable energy on the distribution network side:

[0063]

[0064] In the formula, and They represent the upper and lower limits of active power of renewable energy power stations in the distribution network respectively; and They represent the upper and lower reactive power limits of the renewable energy power station in the distribution network respectively;

[0065] Distribution network side node voltage constraints:

[0066]

[0067] In the formula, and They represent the upper and lower limits of the voltage amplitude of the distribution network respectively;

[0068] Thermal stability constraints of distribution network side lines:

[0069]

[0070] In the formula, It represents the line apparent power of the branch between node i and node j in the distribution network; and They respectively represent the upper and lower limits of the apparent power of the lines in the distribution network.

[0071] The technical solution of the embodiment of the present invention has at least the following advantages and beneficial effects:

[0072] The present invention provides a method for selecting and sizing energy storage sites in coordination with transmission and distribution networks. The method aims to solve the problems of wind abandonment, solar abandonment and voltage over-limit caused by high-penetration photovoltaic and wind power access. The method can combine the topological structure of the transmission and distribution network and the line parameters to achieve coordinated optimization of energy storage configuration in the transmission and distribution networks. The Aitkin acceleration method is used to achieve rapid convergence of power flow calculations, thereby determining the optimal installation location and capacity of energy storage from the perspective of the transmission and distribution networks as a whole, and achieving optimal energy storage configuration. BRIEF DESCRIPTION OF THE DRAWINGS

[0073] Figure 1 An exemplary schematic diagram of a typical wiring diagram of a distribution network including distributed photovoltaics provided by the present invention;

[0074] Figure 2 A topological diagram of a simple example system provided by the present invention;

[0075] Figure 3 This is the topology diagram of the T24D2 example system provided by the present invention. DETAILED DESCRIPTION

[0076] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0077] The present invention proposes a method for selecting a location and determining the capacity of transmission and distribution coordinated energy storage based on the Aitkin acceleration method, which includes the following contents:

[0078] S1 processes the hub node voltage and hub node phase angle to obtain the installation location and installation capacity of the distribution network energy storage. The hub node voltage refers to the voltage of the hub node. The hub node phase angle refers to the phase angle of the hub node. For example, the hub node can be Figure 1 Middle U 0 The node at .

[0079] Several initial voltage values, phase angle values ​​and capacity values ​​for the cycle can be obtained through transmission and distribution coordinated power flow calculation.

[0080] Among them, the expressions for the power flow calculation of the transmission network, the power flow calculation of the distribution network and the power flow calculation of the hub node are:

[0081]

[0082] In the formula, T represents the transmission network; D represents the distribution network; B represents the hub node; Under the premise that the loads of the transmission network and the distribution network and the output of renewable energy included are known, F T (U T , S B , U B ,θ B )=0 indicates the power flow calculation of the transmission network. The voltage and phase angle of the hub node can be calculated according to the net load capacity of the hub node; F D (U D , S B , U B ,θ B ) represents the distribution network flow calculation. According to the hub node voltage and phase angle, the hub node net load capacity can be calculated; F B (U B ,θ B )=0 means the hub node power flow calculation, the sum of the transmission network injection capacity and the distribution network output capacity is 0; U T Represents the voltage of the transmission network; S B represents the hub node capacity; U B represents the hub node voltage; θ B represents the phase angle of the hub node; U D Indicates the distribution network voltage.

[0083] The specific steps of the calculation are as follows:

[0084] S11 obtains the initial installation position and initial installation capacity of the distribution network energy storage according to the initial hub node voltage and the initial hub node phase angle. The initial hub node voltage and the initial hub node phase angle here can be obtained by setting, for example, they can be set to 1 and 0.

[0085] S12 performs distribution network flow calculation and hub node flow calculation on the initial installation position and the initial installation capacity according to the load of each node in the distribution network and the output of the renewable energy included, to obtain the initial hub node capacity.

[0086] S13 performs transmission network power flow calculation and hub node power flow calculation on the initial hub node capacity according to the hub node capacity, the load of each node in the transmission network and the output of renewable energy included, to obtain the first hub node voltage and the first hub node phase angle.

[0087] S14 uses the first hub node voltage as the initial hub node voltage, and uses the first hub node phase angle as the initial hub node phase angle, and repeats S11-S13 until multiple hub node capacities, multiple hub node voltages, and multiple hub node phase angles are obtained; the multiple hub node capacities include at least the initial hub node capacity, the first hub node capacity, and the second hub node capacity; the multiple hub node voltages include at least the first hub node voltage and the second hub node voltage; the multiple hub node phase angles include at least the first hub node phase angle and the second hub node phase angle. The initial hub node capacity, the first hub node capacity, and the second hub node capacity are hub node capacities of multiple cycles obtained through multiple power flow calculations. The first hub node voltage and the second hub node voltage are hub node voltages of multiple cycles obtained through multiple power flow calculations. The first hub node phase angle and the second hub node phase angle are hub node phase angles of multiple cycles obtained through multiple power flow calculations. For example, the first cycle obtains the capacity of the first hub node, the voltage of the first hub node and the phase angle of the first hub node, the second cycle obtains the capacity of the second hub node, the voltage of the second hub node and the phase angle of the second hub node, the third cycle obtains the capacity of the third hub node, and then the Aitkin acceleration method is used to calculate the modified hub node capacity according to the capacity of the first hub node, the capacity of the second hub node and the capacity of the third hub node; the modified hub node capacity is used to obtain the modified hub node voltage and phase angle, and the hub node voltage and phase angle are updated by the first hub node voltage and phase angle, the second hub node voltage and phase angle and the modified hub node voltage and phase angle to obtain a new hub node voltage and phase angle, and then the update operation is continued according to the two latest hub node voltages and phase angles obtained by the update and the modified hub node voltage and phase angle until the hub node voltage U B The error reaches the convergence accuracy and the phase angle θ of the hub node between two adjacent calculations B When the error reaches the convergence accuracy, the power flow calculation ends.

[0088] It also includes optimizing the voltage of the first hub node and the phase angle of the first hub node through the global model of transmission and distribution coordinated energy storage site selection and capacity optimization. Through the global model of transmission and distribution coordinated energy storage site selection and capacity optimization, the system can maximize the access of renewable energy under the minimum configuration of energy storage devices. The expression of the global objective function of the global model of transmission and distribution coordinated energy storage site selection and capacity optimization is:

[0089]

[0090] Where, f represents the global objective function of the global model for optimizing the location and capacity of transmission and distribution coordinated energy storage; max(*) represents the maximum value; min(*) represents the minimum value; represents the renewable energy capacity connected to the transmission grid; represents the renewable energy capacity connected to the distribution network, S ESS Represents the energy storage configuration capacity of the system. Considering that photovoltaic power stations and wind farms are generally uniformly configured with energy storage before being connected to the transmission network, as well as the current cost of energy storage batteries, this invention focuses on configuring energy storage on the distribution network side. Therefore, the optimization goal on the transmission network side is to maximize the system's renewable energy absorption capacity, and the optimization goal on the distribution network side is to achieve the optimal configuration of energy storage location and capacity. The model can be divided into a transmission network side optimization model and a distribution network side optimization model.

[0091] The expression of the transmission network side objective function of the global objective function is:

[0092]

[0093] In the formula, f 1 represents the objective function of the transmission network side in the global model of transmission and distribution coordinated energy storage site selection and capacity optimization; t represents the time of power flow calculation; ∑ t (*) indicates the sum of all tidal current moments; represents the renewable energy capacity connected to the transmission grid at time t; represents the renewable energy capacity connected to the distribution network at time t;

[0094] The constraints on the transmission grid side include:

[0095] Power balance constraints on the transmission grid side:

[0096]

[0097] In the formula, and They represent the active power and reactive power generated by the generator connected to the transmission network at time t respectively; and They represent the active power and reactive power generated by the renewable energy power station connected to the transmission grid at time t respectively; and They represent the active and reactive power of the load on the transmission grid side at time t respectively; P B,t and Q B,t They represent the node active power and node reactive power of the hub node at time t respectively; j represents the second node variable; i represents the first node variable; U i represents the node voltage at node i; U j represents the node voltage at node j; G ij and B ij Respectively represent the conductance and susceptance of the branch between node i and node j; θ ijIndicates the node phase angle of the branch between node i and node j; cos indicates the cosine function; sin indicates the sine function. Among them, i, j and k can refer to different nodes, for example, i can refer to the energy storage installation node variable, j can refer to the ordinary node variable, and k can refer to the over-limit node variable.

[0098] Active power output constraints and reactive power output constraints of generators on the transmission grid side:

[0099]

[0100] In the formula, and Respectively represent the upper limit and lower limit of the motor active power; and Respectively represent the upper and lower limits of reactive power of the generator;

[0101] Active and reactive output constraints of renewable energy on the transmission grid side

[0102]

[0103] In the formula, and They represent the upper and lower limits of active power of renewable energy power stations in the transmission network respectively; and They represent the upper and lower reactive power limits of the renewable energy power station in the transmission network respectively;

[0104] Transmission grid side node voltage constraints:

[0105]

[0106] In the formula, and They represent the upper and lower limits of the voltage amplitude of the transmission network respectively;

[0107] Thermal stability constraints of transmission line on the grid side:

[0108]

[0109] In the formula, represents the line apparent power of the branch between node i and node j in the transmission network; and They represent the upper and lower limits of apparent power of the lines in the transmission network respectively;

[0110] The expression of the distribution network side objective function of the global objective function is:

[0111] f 2 =minS ESS ;

[0112] The constraints on the distribution network side include:

[0113] Power balance constraints on the distribution network side:

[0114]

[0115] Where, t represents the time of power flow calculation; P B,t and Q B,t Respectively represent the active power and reactive power of the hub node; and They represent the active power and reactive power generated by the distributed renewable energy sources connected to the distribution network respectively; and They represent the active and reactive power of the load on the distribution network side respectively; and They represent the active and reactive power of the energy storage device connected to the distribution network side; U i represents the node voltage at node i; U j represents the node voltage at node j; G ij and B ij Respectively represent the conductance and susceptance of the branch between node i and node j; θ ij represents the node phase angle of the branch between node i and node j; cos represents the cosine function; sin represents the sine function;

[0116] Active and reactive output constraints of distributed renewable energy on the distribution network side:

[0117]

[0118] In the formula, and They represent the upper and lower limits of active power of renewable energy power stations in the distribution network respectively; and They represent the upper and lower reactive power limits of the renewable energy power station in the distribution network respectively;

[0119] Distribution network side node voltage constraints:

[0120]

[0121] In the formula, and They represent the upper and lower limits of the voltage amplitude of the distribution network respectively;

[0122] Thermal stability constraints of distribution network side lines:

[0123]

[0124] In the formula, It represents the line apparent power of the branch between node i and node j in the distribution network; and They respectively represent the upper and lower limits of the apparent power of the lines in the distribution network.

[0125] Installation location for energy storage

[0126] like Figure 1 As shown in the figure, the installation location of the energy storage in the distribution network can be obtained by linearly analyzing the voltage and capacity on the distribution network side, including:

[0127] For a radioactive distribution network with N nodes, the starting node is defined as a balance node, and its voltage is U 0 , the line impedance between node k-1 and node k is r k +jx k The pre-connection voltage of each node in the distribution network is determined by the node voltage model of network loss. The pre-connection voltage refers to the voltage of each node in the distribution network before the energy storage is connected. The pre-connection voltage of node k is:

[0128]

[0129] Where U k represents the voltage of node k before access; U 0 represents the voltage of the balancing node; j represents the second node variable; k represents the third node variable; i represents the first node variable; N represents the total number of distribution network nodes; P i and Q i They represent the active power and reactive power of node i after it is connected to the load; P PV,i and Q PV,i They represent the active power and reactive power of node i after it is connected to photovoltaic power generation. LOSS,i and Q LOSS,i Respectively represent the active power loss and reactive power loss of node i; U j represents the voltage of node j before access; r j and x j They represent the inter-node resistance and inter-node reactance of the inter-node lines respectively.

[0130] Determine the post-connection voltage of each node after the energy storage is connected to the distribution network. The post-connection voltage refers to the voltage of each node after the distribution network is connected to the energy storage. The post-connection voltage of node k is:

[0131]

[0132] Where U k ' represents the voltage of node k after the energy storage is connected to node i; P ESS,i and Q ESS,i Respectively represent the active power and reactive power of energy storage; Uj ' represents the voltage of node j after the energy storage is connected to node i.

[0133] The difference between the voltage before connection and the voltage after connection is used as the node voltage difference, and the total node resistance and the total node reactance from each node to the balance node are determined.

[0134] In the process, define:

[0135]

[0136] In the formula, It represents the voltage parameter of node j, and represents the average value of the voltage of node j before and after the energy storage is connected.

[0137] Through U k '-U k And U j and U j 'Uniform use Expressed as ΔU k The complete expression is:

[0138]

[0139] After sorting, the expression of node voltage difference is:

[0140]

[0141] In the formula, ΔU k represents the node voltage difference between node k before and after energy storage is connected; R k,i and X k,i They represent the total node resistance and total node reactance from the balancing node to node i, R k,1 and X k,1 They represent the resistance and reactance from the balancing node to node 1, R k,N and X k,N They represent the resistance and reactance from the balancing node to the node N respectively; P ESS,i and Q ESS,i Respectively represent the active power and reactive power of energy storage at node i, P ESS,1 and Q ESS,1 They represent the active power and reactive power of energy storage at node 1, respectively, P ESS,N and Q ESS,N Respectively represent the active power and reactive power of energy storage at node N; P LOSS,ESS,i and Q LOSS,ESS,i They represent the active power loss and reactive power loss of energy storage at node i, respectively, P LOSS,ES,1 and Q LOSS,ESS,1 They represent the active power loss and reactive power loss of energy storage at node 1, respectively, P LOSS,ESS,N and QLOSS,ESS,N They represent the active power loss and reactive power loss of energy storage at node N respectively;

[0142] The expressions for the total resistance of a node and the total reactance of the node are:

[0143] when i <k,

[0144] When i ≥ k,

[0145] In the formula, j represents the second node variable; k represents the third node variable; i represents the first node variable; R k,i and X k,i They represent the total node resistance and total node reactance from the balancing node to node i respectively; r j and x j They represent the inter-node resistance and inter-node reactance of the inter-node lines respectively.

[0146] The power sensitivity coefficient of each node is determined according to the ratio of the total resistance of the node and the total reactance of the node to the voltage of the balancing node; the power sensitivity coefficient includes the active power sensitivity coefficient and the reactive power sensitivity coefficient. k The active power sensitivity and reactive power sensitivity coefficients of node i are: and When the line models are consistent, the sensitivity coefficient is proportional to the length between node i and the balance node 0.

[0147] Since the sensitivity coefficient is only related to the line resistance and reactance, the node voltage change is linearly related to the node power. Therefore, the installation position can be determined according to the power sensitivity coefficient, including: for a single node voltage over-limit, the over-limit node is used as the installation position of the energy storage; for multiple node voltage over-limit, the over-limit node farthest from the balancing node is used as the installation position of the energy storage. Specifically, for the single node voltage over-limit problem, when the energy storage device is used to manage the voltage over-limit of node k, the power sensitivity coefficients of the nodes before node k are all less than the power sensitivity coefficient of node k, and node k and the subsequent nodes have the same power sensitivity coefficient. Considering that the farther away from the balancing node 0, the greater the line loss generated when the energy storage is charged, node k is selected as the energy storage installation position. When multiple nodes have voltage over-limit, the point with the largest node number in the overvoltage node, that is, the point farthest from the balancing node, is selected as the energy storage installation position, so that the sensitivity coefficient of the previous voltage over-limit point to energy storage can be maximized, and the energy storage capacity can be fully utilized.

[0148] For energy storage installation capacity

[0149] When the energy storage is connected, the node voltage becomes i

[0150]

[0151] Among them, P LOSS,ES,i is the change in line loss caused by energy storage before and after installing energy storage.

[0152] Then the expressions for the active power and reactive power of the energy storage at the node are:

[0153]

[0154] The expressions for the active power loss and reactive power loss of the energy storage at the node are:

[0155]

[0156] In the formula, P ESS,i and Q ESS,i respectively represent the active power and reactive power of the energy storage at node i; represents the voltage parameter of node j, which is the average value of the voltage of node j before and after the energy storage is connected; ΔU k represents the node voltage difference of node k before and after the energy storage is connected; j represents the second node variable; k represents the third node variable; i represents the first node variable; r j and x j respectively represent the inter-node resistance and inter-node reactance of the line between nodes; P LOSS,ESS,i and Q LOSS,ESS,i respectively represent the active power loss and reactive power loss of the energy storage at node i.

[0157] When there are three over-limit nodes l, h, and c, and the numbers are l < h < c, that is, point c is the farthest from the balanced node position, then point c is selected as the energy storage installation position. The active power and reactive power of the energy storage are calculated as follows, and the expression for the installed capacity of the distribution network energy storage is obtained:

[0158]

[0159] In the formula, P ESS and Q ESS respectively represent the active power and reactive power of the installed energy storage; max represents taking the maximum value; P ESS,l and Q ESS,l respectively represent the active power and reactive power of the node numbered l; P ESS,h and Q ESS,h respectively represent the active power and reactive power of the node numbered h; P ESS,c and Q ESS,c respectively represent the active power and reactive power of the node numbered c; s.t represents the constraint condition; ΔU uIndicates the voltage difference that needs to be reduced for the voltage at the over-limit node u to change from the over-limit value to the maximum normal value (for example, 10kV); U u represents the voltage over-limit value at the over-limit node u, u represents the node variable over-limit in this example, and its value is l, h or c; U max Indicates the maximum normal value of the voltage when the node is running; ΔU l , ΔU h and ΔU c Respectively represent the voltage difference that needs to be reduced for the voltage at nodes l, h and c to change from the over-limit value to the normal value; R k,l and X k,l They represent the total node resistance and total node reactance from node k to node l respectively; R k,h and X k,h They represent the total node resistance and total node reactance from node k to node h respectively; R k,c and X k,c They represent the total node resistance and total node reactance from node k to node c respectively. By installing a capacity of P at the node that exceeds the limit, ESS and Q ESS The energy storage can reduce the voltage value of the out-of-limit node to the normal voltage range.

[0160] S2 performs distribution network power flow calculation and hub node power flow calculation on the installation location and the installation capacity to obtain hub node capacity. Hub node capacity refers to the capacity transmitted from the transmission network to the distribution network.

[0161] S3 corrects the hub node capacity by using the Aitkin acceleration method to obtain a corrected hub node capacity.

[0162] The expression for modifying the hub node capacity is:

[0163]

[0164] Among them, S' B,k+1 represents the modified hub node capacity; S B,k represents the initial hub node capacity; S B,k+1 represents the capacity of the first hub node; S B,k+1 Represents the capacity of the second hub node.

[0165] S4 performs transmission network power flow calculation and hub node power flow calculation on the modified hub node capacity to obtain a modified hub node voltage and a modified hub node phase angle.

[0166] S5 processes the modified hub node voltage and the modified hub node phase angle by using the Aitkin acceleration method to update the hub node voltage and the hub node phase angle;

[0167] The expression for updating the hub node voltage is:

[0168]

[0169] The expression for updating the phase angle of the pivot node is:

[0170]

[0171] In the formula, U' B,k+1 and θ' B,k+1 Respectively represent the updated hub node voltage and hub node phase angle; U B,k and θ B,k Respectively represent the first hub node voltage and the first hub node phase angle; U B,k+1 and θ B,k+1 Respectively represent the second hub node voltage and the second hub node phase angle; U B,k+2 and θ B,k+2 represent the modified hub node voltage and the modified hub node phase angle respectively.

[0172] S6 repeats S1-S5 until the hub node voltage and the hub node phase angle both meet the error threshold. For example, until the voltage and phase angle errors both meet 10-4, the power flow calculation ends.

[0173] Example 1

[0174] like Figure 2 As shown in the figure, in the simple example system, the 10kV line, the feeder port voltage is 10kV, the line impedance between each node is 0.1+j0.05Ω, the loads connected to each node are 100+j30kW, 100+j20kW, 200+j50kW and 400+j60kW respectively; node 3 is connected to photovoltaic 3500kWp. The voltages of each node before and after node 3 is connected to photovoltaic are shown in Table 1.

[0175] Table 1 Simple example of voltage at each node before and after photovoltaic connection (kV)

[0176] Node Number 0 1 2 3 4 Voltage before photovoltaic connection 10.0000 9.9912 9.9835 9.9769 9.9726 Voltage after photovoltaic connection 10.0000 10.0259 10.0530 10.0812 10.0769

[0177] As shown in Table 1, after the photovoltaic power plant is connected, the voltage of nodes 3 and 4 exceeds the upper limit of +7%. The voltage control goal is to restore the voltage of the node that exceeds the upper limit to 10.07.

[0178] 1.1 Energy storage installation location selection

[0179] (1) The voltage at node 3 exceeds the limit. Energy storage is installed at nodes 1, 2, 3, and 4, and their active power sensitivity coefficients are 0.1, 0.2, 0.3, and 0.3, respectively. Considering the reduction of losses, node 3 is selected as the energy storage installation location.

[0180] (2) The voltage at node 4 exceeds the limit. Energy storage is installed at nodes 1, 2, 3, and 4, and their active power sensitivity coefficients are 0.1, 0.2, 0.3, and 0.4, respectively. Node 4 is selected as the energy storage installation location.

[0181] 1.2 Energy storage installation capacity selection

[0182] (1) Node 3 energy storage installation capacity requirements

[0183] U 3 =(10.08112+10.07) / 2=10.0756kVΔU=10.08112-10.07=0.0112kV

[0184]

[0185] (2) Node 4 energy storage installation capacity requirements

[0186] ΔU=10.0769-10.07=0.0069kV

[0187]

[0188] (3) Energy storage capacity selection and verification

[0189]

[0190] At the access location, the energy storage capacity is 376.5kW.

[0191] 1.3 Location Verification

[0192] When the 376.5kW energy storage is connected to nodes 1 and 2, the voltages of each node are as shown in Table 2:

[0193] Table 2: When 376.5kW energy storage is connected to nodes 1 and 2, the voltage at each node

[0194]

[0195]

[0196] It can be seen that when the energy storage of the same capacity is installed at nodes 1 and 2, it cannot solve the voltage over-limit problem, but installing it at node 4 can solve the voltage over-limit problem.

[0197] Table 3 350kW, 376.5kW and 385kW energy storage are connected to node 3 respectively. The voltage of each node

[0198]

[0199] As can be seen from the above table, the capacity calculated by the present invention can meet the voltage upper limit requirement with an error of 10-4, which meets the engineering requirements. If the capacity is lower than this, the voltage upper limit requirement cannot be met, and if the capacity is higher than this, capacity waste will be caused.

[0200] Example 2

[0201] like Figure 3 As shown in the figure, G represents generator, Bus represents bus, and PV represents photovoltaic access. For the T24D2 example, two IEEE 33 distribution networks are connected to the IEEE RTS24 transmission network. The transmission network contains 10 generators and 38 transmission lines, and the distribution network is connected to bus No. 1 and No. 7 of the transmission network. The parameters of renewable energy access to the transmission network are shown in Table 4; the parameters of distributed photovoltaic and wind power access to the distribution network are shown in Table 5.

[0202] Table 4. Renewable energy capacity connected to the transmission grid

[0203]

[0204] Table 5 Capacity of distributed power sources connected to the distribution grid

[0205]

[0206] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for selecting a location and determining the capacity of energy storage for transmission and distribution coordination based on the Aitkin acceleration method, characterized in that: include: S1 processes the hub node voltage and hub node phase angle to obtain the installation location and installation capacity of the distribution network energy storage; S2 performs distribution network power flow calculation and hub node power flow calculation on the installation location and the installation capacity to obtain hub node capacity; S3 corrects the hub node capacity by using the Aitkin acceleration method to obtain a corrected hub node capacity; S4 performs transmission network power flow calculation and hub node power flow calculation on the modified hub node capacity to obtain a modified hub node voltage and a modified hub node phase angle; S5 processes the modified hub node voltage and the modified hub node phase angle by using the Aitkin acceleration method to update the hub node voltage and the hub node phase angle; S6 repeats S1-S5 until the hub node voltage and the hub node phase angle simultaneously meet the error threshold.

2. The method for selecting a location and determining the capacity of energy storage for transmission and distribution coordination based on the Aitkin acceleration method according to claim 1 is characterized in that: Get the installation location of the distribution network energy storage, including: Determine the pre-connection voltage of each node in the distribution network; Determining the post-connection voltage of each node after the energy storage is connected to the distribution network; Taking the difference between the voltage before connection and the voltage after connection as the node voltage difference, and determining the total node resistance and total node reactance from each node to the balance node; Determine the power sensitivity coefficient of each node according to the ratio of the total resistance of the node and the total reactance of the node to the voltage of the balancing node; the power sensitivity coefficient includes an active power sensitivity coefficient and a reactive power sensitivity coefficient; The installation location is determined according to the power sensitivity coefficient, including: for a single-node voltage exceeding a limit, the exceeding-limit node is used as the installation location of the energy storage; for multiple-node voltage exceeding a limit, the exceeding-limit node farthest from the balancing node is used as the installation location of the energy storage.

3. The method for selecting a location and determining the capacity of energy storage for transmission and distribution coordination based on the Aitkin acceleration method according to claim 2 is characterized in that: The expression of the node voltage difference is: In the formula, ΔU k represents the node voltage difference between node k before and after energy storage is connected; R k,i and X k,i They represent the total node resistance and total node reactance from the balancing node to node i, R k,1 and X k,1 They represent the resistance and reactance from the balancing node to node 1, R k,N and X k,N They represent the resistance and reactance from the balancing node to the node N respectively; P ESS,i and Q ESS,i Respectively represent the active power and reactive power of energy storage at node i, P ESS,1 and Q ESS,1 They represent the active power and reactive power of energy storage at node 1, respectively, P ESS,N and Q ESS,N Respectively represent the active power and reactive power of energy storage at node N; P LOSS,ESS,i and Q LOSS,ESS,i They represent the active power loss and reactive power loss of energy storage at node i, respectively, P LOSS,ES,1 and Q LOSS,ESS,1 They represent the active power loss and reactive power loss of energy storage at node 1, respectively, P LOSS,ESS,N and Q LOSS,ESS,N They represent the active power loss and reactive power loss of energy storage at node N respectively; The expressions of the total resistance of the node and the total reactance of the node are: This <k, When i ≥ k, In the formula, j represents the second node variable; k represents the third node variable; i represents the first node variable; R k,i and X k,i They represent the total node resistance and total node reactance from the balancing node to node i respectively; r j and x j They represent the inter-node resistance and inter-node reactance of the inter-node lines respectively.

4. The method for selecting a location and determining the capacity of energy storage for transmission and distribution coordination based on the Aitkin acceleration method according to claim 2 is characterized in that: When there are three out-of-limit nodes, l, h and c, the expression of the installed capacity of the distribution network energy storage is: Where P ESS and Q ESS Respectively represent the active power and reactive power of the energy storage installation; max represents the maximum value; P ESS,l and Q ESS,l They represent the active power and reactive power of the node numbered l respectively; P ESS,h and Q ESS,h They represent the active power and reactive power of the node numbered h respectively; P ESS,c and Q ESS,c They represent the active power and reactive power of the node numbered c; st represents the constraint condition; ΔU u Indicates the voltage difference that needs to be reduced for the voltage at the over-limit node u to change from the over-limit value to the maximum normal value; U u Indicates the voltage over-limit value at the over-limit node u, u represents the node variable of the over-limit node, and its value is l, h or c; U max Indicates the maximum normal value of the voltage when the node is running; ΔU l , ΔU h and ΔU c Respectively represent the voltage difference that needs to be reduced for the voltage at nodes l, h and c to change from the over-limit value to the normal value; R k,l and X k,l They represent the total node resistance and total node reactance from node k to node l respectively; R k,h and X k,h They represent the total node resistance and total node reactance from node k to node h respectively; R k,c and X k,c They represent the total node resistance and total node reactance from node k to node c respectively.

5. The method for selecting a location and determining the capacity of transmission and distribution coordinated energy storage based on the Aitkin acceleration method according to claim 4 is characterized in that: The expressions of active power and reactive power of energy storage at the node are: The expressions of active power loss and reactive power loss of energy storage at the node are: Where P ESS,i and Q ESS,i represent the active power and reactive power of energy storage at node i respectively; Represents the voltage parameter of node j, which is the average value of the voltage of node j before and after energy storage is connected; ΔU k represents the node voltage difference between node k before and after energy storage is connected; j represents the second node variable; k represents the third node variable; i represents the first node variable; r j and x j They represent the inter-node resistance and inter-node reactance of the inter-node line respectively; P LOSS,ESS,i and Q LOSS,ESS,i They represent the active power loss and reactive power loss of the energy storage at node i respectively.

6. The method for selecting a location and determining the capacity of energy storage for transmission and distribution coordination based on the Aitkin acceleration method according to claim 1, characterized in that: The expression for modifying the hub node capacity is: Among them, S' B,k+1 represents the modified hub node capacity; S B,k represents the initial hub node capacity; S B,k+1 represents the capacity of the first hub node; S B,k+1 Represents the capacity of the second hub node.

7. The method for selecting a location and determining the capacity of energy storage for transmission and distribution coordination based on the Aitkin acceleration method according to claim 1, characterized in that: The expression for updating the hub node voltage is: The expression for updating the phase angle of the pivot node is: In the formula, U' B,k+1 and θ' B,k+1 Respectively represent the updated hub node voltage and hub node phase angle; U B,k and θ B,k Respectively represent the first hub node voltage and the first hub node phase angle; U B,k+1 and θ B,k+1 Respectively represent the second hub node voltage and the second hub node phase angle; U B,k+2 and θ B,k+2 represent the modified hub node voltage and the modified hub node phase angle respectively.

8. The method for selecting a location and determining the capacity of transmission and distribution coordinated energy storage based on the Aitkin acceleration method according to any one of claims 1 to 7, characterized in that: Acquiring the hub node voltage, the hub node phase angle, and the hub node capacity further includes: S11 obtains the initial installation position and initial installation capacity of the distribution network energy storage according to the initial hub node voltage and the initial hub node phase angle; S12 performs distribution network power flow calculation and hub node power flow calculation on the initial installation position and the initial installation capacity to obtain an initial hub node capacity; S13 performs transmission network power flow calculation and hub node power flow calculation on the initial hub node capacity to obtain a first hub node voltage and a first hub node phase angle; S14 uses the first hub node voltage as the initial hub node voltage, and uses the first hub node phase angle as the initial hub node phase angle, and repeats S11-S13 until multiple hub node capacities, multiple hub node voltages, and multiple hub node phase angles are obtained; the multiple hub node capacities include at least the initial hub node capacity, the first hub node capacity, and the second hub node capacity; the multiple hub node voltages include at least the first hub node voltage and the second hub node voltage; the multiple hub node phase angles include at least the first hub node phase angle and the second hub node phase angle.

9. The method for selecting a location and determining the capacity of transmission and distribution coordinated energy storage based on the Aitkin acceleration method according to claim 8, characterized in that: The expressions for the power flow calculation of the transmission network, the power flow calculation of the distribution network and the power flow calculation of the hub node are: In the formula, T represents the transmission network; D represents the distribution network; B represents the hub node; F T (U T , S B , U B ,θ B )=0 means power flow calculation of transmission network; F D (U D , S B , U B ,θ B ) represents the distribution network power flow calculation; F B (U B ,θ B )=0 means hub node power flow calculation; U T Represents the voltage of the transmission network; S B represents the hub node capacity; U B represents the hub node voltage; θ B represents the phase angle of the hub node; U D Indicates the distribution network voltage.

10. The method for selecting a location and determining the capacity of transmission and distribution coordinated energy storage based on the Aitkin acceleration method according to claim 9, characterized in that: The method also includes optimizing the voltage of the first hub node and the phase angle of the first hub node through a global model for optimizing the location and capacity of transmission and distribution coordinated energy storage; the expression of the global objective function of the global model for optimizing the location and capacity of transmission and distribution coordinated energy storage is: Where, f represents the global objective function of the global model for optimizing the location and capacity of transmission and distribution coordinated energy storage; max(*) represents the maximum value; min(*) represents the minimum value; represents the renewable energy capacity connected to the transmission grid; represents the renewable energy capacity connected to the distribution network, S ESS Indicates the energy storage configuration capacity of the system; The expression of the transmission network side objective function of the global objective function is: Where f1 represents the objective function of the transmission network in the global optimization model of transmission and distribution coordinated energy storage site selection and capacity determination; t represents the time of power flow calculation; ∑ t (*) indicates the sum of all tidal current moments; represents the renewable energy capacity connected to the transmission grid at time t; represents the renewable energy capacity connected to the distribution network at time t; The constraints on the transmission grid side include: Power balance constraints on the transmission grid side: In the formula, and They represent the active power and reactive power generated by the generator connected to the transmission network at time t respectively; and They represent the active power and reactive power generated by the renewable energy power station connected to the transmission grid at time t respectively; and They represent the active and reactive power of the load on the transmission grid side at time t respectively; P B,t and Q B,t They represent the node active power and node reactive power of the hub node at time t respectively; j represents the second node variable; i represents the first node variable; U i represents the node voltage at node i; U j represents the node voltage at node j; G ij and B ij Respectively represent the conductance and susceptance of the branch between node i and node j; θ ij represents the node phase angle of the branch between node i and node j; cos represents the cosine function; sin represents the sine function; Active power output constraints and reactive power output constraints of generators on the transmission grid side: In the formula, and Respectively represent the upper limit and lower limit of the motor active power; and Respectively represent the upper and lower limits of reactive power of the generator; Active and reactive output constraints of renewable energy on the transmission grid side In the formula, and They represent the upper and lower limits of active power of renewable energy power stations in the transmission network respectively; and They represent the upper and lower reactive power limits of the renewable energy power station in the transmission network respectively; Transmission grid side node voltage constraints: In the formula, and They represent the upper and lower limits of the voltage amplitude of the transmission network respectively; Thermal stability constraints of transmission line on the grid side: In the formula, represents the line apparent power of the branch between node i and node j in the transmission network; and They represent the upper and lower limits of apparent power of the lines in the transmission network respectively; The expression of the distribution network side objective function of the global objective function is: f2=minS ESS ; The constraints on the distribution network side include: Power balance constraints on the distribution network side: Where, t represents the time of power flow calculation; P B,t and Q B,t Respectively represent the active power and reactive power of the hub node; and They represent the active power and reactive power generated by the distributed renewable energy sources connected to the distribution network respectively; and They represent the active and reactive power of the load on the distribution network side respectively; and They represent the active and reactive power of the energy storage device connected to the distribution network side; U i represents the node voltage at node i; U j represents the node voltage at node j; G ij and B ij Respectively represent the conductance and susceptance of the branch between node i and node j; θ ij represents the node phase angle of the branch between node i and node j; cos represents the cosine function; sin represents the sine function; Active and reactive output constraints of distributed renewable energy on the distribution network side: In the formula, and They represent the upper and lower limits of active power of renewable energy power stations in the distribution network respectively; and They represent the upper and lower reactive power limits of the renewable energy power station in the distribution network respectively; Distribution network side node voltage constraints: In the formula, and They represent the upper and lower limits of the voltage amplitude of the distribution network respectively; Thermal stability constraints of distribution network side lines: In the formula, It represents the line apparent power of the branch between node i and node j in the distribution network; and They respectively represent the upper and lower limits of the apparent power of the lines in the distribution network.

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