Optimized operation method, device and equipment for flexible interconnected power distribution network and medium

Abstract

The invention relates to an optimized operation method, device, equipment and medium for a flexible interconnected power distribution network, and the method comprises the steps: carrying out the approximate linearization of a nonlinear power flow calculation equation of an AC part of an AC / DC power distribution network, and constructing a DC power flow model of the AC part; approximately linearizing the nonlinear power flow calculation equation of the DC part of the AC / DC power distribution network, and constructing a DC power flow model of the DC part; taking the minimum network loss of the flexible interconnected power distribution network as a target, taking the direct current power flow model of the alternating current part and the direct current power flow model of the direct current part as constraints, and constructing an optimized operation model of the flexible interconnected power distribution network; solving the optimized operation model of the flexible interconnected power distribution network to obtain an optimized operation scheme of the flexible interconnected power distribution network; and controlling the flexible interconnected power distribution network to operate according to the optimized operation scheme of the flexible interconnected power distribution network. According to the method, large-scale nonlinear constrained cone relaxation can be avoided, and the efficiency of optimization operation is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of distribution network planning and optimization dispatching, and in particular to a method, device, equipment and medium for optimizing operation of a flexible interconnected distribution network. Background Art

[0002] As a new form of distribution network, flexible AC / DC interconnected distribution network has potential advantages in new energy and new DC load power supply modes. As a new type of distribution equipment, flexible interconnected device (FID) plays an important role in improving the new energy carrying capacity of AC / DC interconnected distribution network, and has received extensive attention in the medium and low voltage system of distribution network. As a flexible interconnected device, FID aims to replace traditional circuit breaker interconnection switches with controllable power electronic equipment, realize flexible connection between feeders, and provide high-efficiency control and power flow optimization.

[0003] At present, the optimization scheduling of existing flexible interconnection switches usually requires first predicting the output of distribution network sources and loads, and then establishing a model with the maximum access capacity of new energy and the minimum network loss as the optimization objectives according to the topological structure of the distribution network and the operating characteristics of the physical equipment in the network. The decision variables of this model include not only the access position (0-1 variable) and access capacity (integer variable) of the flexible interconnection switch, but also the operating power (continuous variable) of the access equipment. In addition, the power balance constraint in this model is a non-convex nonlinear constraint. There are two existing methods for dealing with this nonlinear constraint: 1) piecewise linearization, which uses the piecewise linearization method to obtain the approximate optimal solution of the high-order non-convex model; 2) second-order cone relaxation, which converts the model into a second-order cone programming model for solution through second-order cone relaxation. The linearization method generally relaxes the constraints to decouple the nonlinear power flow, which can achieve good results in a relatively single application scenario, but it often changes the physical meaning of the power flow and makes it difficult to ensure the feasibility of the solution area. The second-order cone relaxation method requires setting an appropriate objective function to drive the second-order cone relaxation to gradually "tighten" the optimal solution. The "relaxation" conditions are relatively harsh, the versatility is not high, and the solution convergence is poor. As the scale of the distribution network increases, the relaxation of a large number of constraints will greatly affect the speed of model solution and cannot adapt to fast optimization solutions. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a method, device, equipment and medium for optimizing the operation of a flexible interconnected distribution network, which can avoid cone relaxation of large-scale nonlinear constraints and improve the efficiency of optimization operations.

[0005] The technical solution adopted by the present invention to solve the technical problem is: to provide a method for optimizing operation of a flexible interconnected distribution network, comprising the following steps:

[0006] The nonlinear power flow calculation equation of the AC part of the AC / DC distribution network is approximately linearized, and a DC power flow model of the AC part is constructed;

[0007] The nonlinear power flow calculation equation of the DC part of the AC / DC distribution network is approximately linearized to construct a DC power flow model of the DC part;

[0008] With the goal of minimizing the network loss of the flexible interconnected distribution network, and with the DC power flow model of the AC part and the DC power flow model of the DC part as constraints, an optimal operation model of the flexible interconnected distribution network is constructed;

[0009] Solving the optimal operation model of the flexible interconnected distribution network to obtain an optimal operation plan for the flexible interconnected distribution network;

[0010] The flexible interconnected distribution network is controlled to operate according to the flexible interconnected distribution network optimization operation plan.

[0011] The DC power flow model of the AC part is expressed as: ΔS = A s ·ΔV, where ΔS is the node injection power correction vector, ΔV is the correction vector of the node voltage amplitude reference value vector, A s =diag[Y + V b ]+diag[V b ]Y + , V b is the node voltage amplitude reference value vector, Y + is the admittance matrix.

[0012] The DC power flow model of the DC part is expressed as: L =B s V, where P L is the active power vector of the DC line, B s is a constant matrix related to the network topology and line resistance, and V is a vector of the square of the DC node voltage amplitude.

[0013] The objective function of the flexible interconnected distribution network optimization operation model is: Among them, f is the objective function of the flexible interconnected distribution network optimization operation model, T is the number of daily sampling points in the optimization period, N L is the sum of the AC and DC distribution network lines, R ij is the resistance of branch ij, I ij,t is the effective value of the current in branch ij at time t, N SOP is the number of flexible interconnection switches connected to the distribution network, is the active power loss value of the i′th flexible interconnection switch at time t.

[0014] The constraint conditions of the flexible interconnected distribution network optimization operation model include: flexible interconnected switch operation constraints, voltage source converter station operation constraints, line flow constraints based on the DC flow model of the AC part, node voltage constraints based on the DC flow model of the AC part, line flow constraints based on the DC flow model of the DC part, and node voltage constraints based on the DC side DC flow model.

[0015] The flexible interconnection switch operation constraint is expressed as: in, is the active power transmitted by the flexible interconnection switch and the port connected to node i at time t, is the active power transmitted by the port connected to the flexible interconnection switch and node j at time t, is the active power loss value of the port connected to the flexible interconnection switch and node i at time t, is the active power loss value of the port connected to the flexible interconnection switch and node j at time t; is the converter loss coefficient of the flexible interconnection switch connected at node i, is the converter loss coefficient of the flexible interconnection switch connected at node j, is the reactive power transmitted by the flexible interconnection switch and the port connected to node i at time t, is the reactive power transmitted by the port connected to the flexible interconnection switch and node j at time t; i represents the operating state of the flexible interconnection switch connected to node i, σ j represents the operating status of the flexible interconnection switch connected to node j, A N is the set of AC nodes in the AC / DC distribution network, N SOP is the number of flexible interconnection switches connected to the distribution network.

[0016] The voltage source converter station operation constraints are expressed as: Among them, S i,VSC represents the rated apparent power of the voltage source converter station at node i; and are the active power and reactive power injected into the AC side of the voltage source converter station at time t respectively; is the active power flowing out of the DC side of the voltage source converter station at time t; R i,VSC and X i,VSC are the equivalent resistance and reactance of the voltage source converter station at node i; V k,t and V i,t They represent the square of the effective value of the voltage at port k of the voltage source converter station and the square of the effective value of the voltage at node i at time t respectively.

[0017] The line power flow constraint of the DC power flow model based on the AC part is expressed as: The node voltage constraint of the DC power flow model based on the AC part is expressed as: Among them, P ji,t and Q ji,t They represent the active power and reactive power flowing through branch ij at time t respectively; B i is the set of child nodes of node i, A N is the set of AC nodes in the AC / DC distribution network; and are the injected active power and reactive power of node i respectively; and are the active power of distributed renewable energy and load at node i at time t, is the active power transmitted by the flexible interconnection switch and the port connected to node i at time t, is the reactive power transmitted by the flexible interconnection switch and the port connected to node i at time t, and are the active power and reactive power injected into the AC side of the voltage source converter station at time t respectively; is the reactive power of the load on node i at time t; ΔS is the node injection power correction vector, ΔV is the correction vector of the node voltage amplitude reference value vector, V b is the node voltage amplitude reference value vector, Y + is the admittance matrix; ΔS i,t is the correction amount of the power injected into node i, and are the reference values ​​of the voltage amplitudes of nodes i and j respectively; is the element of the admittance matrix, V ui_A and V li_A are the upper and lower limits of the voltage at node i, ΔV i,t is the correction value of the voltage amplitude reference value of node i.

[0018] The line power flow constraint of the DC power flow model based on the DC part is expressed as: The node voltage constraint based on the DC side DC power flow model is expressed as: Among them, P ji,t represents the power flowing through branch ij at time t; B i is the set of child nodes of node i, D N is the set of DC nodes in the AC / DC distribution network, is the injected active power of node i; and are the active power of distributed renewable energy and load at node i at time t, is the active power flowing out of the DC side of the voltage source converter station at time t; P Lis the active power vector of the DC line, B s is the inverse matrix of the constant matrix related to the network topology and line resistance, V is the vector of the square of the DC node voltage amplitude, V ui_D and V li_D are the upper and lower limits of the voltage at node i respectively.

[0019] The technical solution adopted by the present invention to solve the technical problem is: to provide a flexible interconnected distribution network optimization operation device, including:

[0020] The AC part construction module is used to approximately linearize the nonlinear power flow calculation equation of the AC part of the AC / DC distribution network and construct a DC power flow model of the AC part;

[0021] A DC part construction module is used to approximately linearize the nonlinear power flow calculation equation of the DC part of the AC / DC distribution network and construct a DC power flow model of the DC part;

[0022] An operation model building module is used to build an optimized operation model of the flexible interconnected distribution network with the goal of minimizing the network loss of the flexible interconnected distribution network and with the DC power flow model of the AC part and the DC power flow model of the DC part as constraints;

[0023] A solution module, used for solving the flexible interconnected distribution network optimization operation model to obtain the flexible interconnected distribution network optimization operation plan;

[0024] A control module is used to control the operation of the flexible interconnected distribution network according to the flexible interconnected distribution network optimization operation plan.

[0025] The DC power flow model of the AC part constructed by the AC part construction module is expressed as: ΔS=A s ·ΔV, where ΔS is the node injection power correction vector, ΔV is the correction vector of the node voltage amplitude reference value vector, A s =diag[Y + V b ]+diag[V b ]Y + , V b is the node voltage amplitude reference value vector, Y + is the admittance matrix.

[0026] The DC power flow model of the DC part constructed by the DC part construction module is expressed as: L =B s V, where P L is the active power vector of the DC line, B s is a constant matrix related to the network topology and line resistance, and V is a vector of the square of the DC node voltage amplitude.

[0027] The objective function of the flexible interconnected distribution network optimization operation model constructed by the operation model construction module is: Among them, f is the objective function of the flexible interconnected distribution network optimization operation model, T is the number of daily sampling points in the optimization period, N L is the sum of the AC and DC distribution network lines, R ij is the resistance of branch ij, I ij,t is the effective value of the current in branch ij at time t, N SOP is the number of flexible interconnection switches connected to the distribution network, is the active power loss value of the i′th flexible interconnection switch at time t.

[0028] The constraints of the flexible interconnected distribution network optimization operation model constructed by the operation model construction module include: flexible interconnected switch operation constraints, voltage source converter station operation constraints, line flow constraints based on the DC flow model of the AC part, node voltage constraints based on the DC flow model of the AC part, line flow constraints based on the DC flow model of the DC part, and node voltage constraints based on the DC side DC flow model.

[0029] The flexible interconnection switch operation constraint is expressed as: in, is the active power transmitted by the flexible interconnection switch and the port connected to node i at time t, is the active power transmitted by the port connected to the flexible interconnection switch and node j at time t, is the active power loss value of the port connected to the flexible interconnection switch and node i at time t, is the active power loss value of the port connected to the flexible interconnection switch and node j at time t; is the converter loss coefficient of the flexible interconnection switch connected at node i, is the converter loss coefficient of the flexible interconnection switch connected at node j, is the reactive power transmitted by the flexible interconnection switch and the port connected to node i at time t, is the reactive power transmitted by the port connected to the flexible interconnection switch and node j at time t; i represents the operating state of the flexible interconnection switch connected to node i, σ j represents the operating status of the flexible interconnection switch connected to node j, A N is the set of AC nodes in the AC / DC distribution network, N SOP is the number of flexible interconnection switches connected to the distribution network.

[0030] The voltage source converter station operation constraints are expressed as: Among them, S i,VSC represents the rated apparent power of the voltage source converter station at node i; and are the active power and reactive power injected into the AC side of the voltage source converter station at time t respectively; is the active power flowing out of the DC side of the voltage source converter station at time t; R i,VSC and X i,VSC are the equivalent resistance and reactance of the voltage source converter station at node i; V k,t and V i,t They represent the square of the effective value of the voltage at port k of the voltage source converter station and the square of the effective value of the voltage at node i at time t respectively.

[0031] The line power flow constraint of the DC power flow model based on the AC part is expressed as: The node voltage constraint of the DC power flow model based on the AC part is expressed as: Among them, P ji,t and Q ji,t They represent the active power and reactive power flowing through branch ij at time t respectively; B i is the set of child nodes of node i, A N is the set of AC nodes in the AC / DC distribution network; and are the injected active power and reactive power of node i respectively; and are the active power of distributed renewable energy and load at node i at time t, is the active power transmitted by the flexible interconnection switch and the port connected to node i at time t, is the reactive power transmitted by the flexible interconnection switch and the port connected to node i at time t, and are the active power and reactive power injected into the AC side of the voltage source converter station at time t respectively; is the reactive power of the load on node i at time t; ΔS is the node injection power correction vector, ΔV is the correction vector of the node voltage amplitude reference value vector, V b is the node voltage amplitude reference value vector, Y + is the admittance matrix; ΔS i,t is the correction amount of the power injected into node i, and are the reference values ​​of the voltage amplitudes of nodes i and j respectively; is the element of the admittance matrix, V ui_A and V li_A are the upper and lower limits of the voltage at node i, ΔV i,t is the correction value of the voltage amplitude reference value of node i.

[0032] The line power flow constraint of the DC power flow model based on the DC part is expressed as: The node voltage constraint based on the DC side DC power flow model is expressed as: Among them, P ji,t represents the power flowing through branch ij at time t; B i is the set of child nodes of node i, D N is the set of DC nodes in the AC / DC distribution network, is the injected active power of node i; and are the active power of distributed renewable energy and load at node i at time t, is the active power flowing out of the DC side of the voltage source converter station at time t; P L is the active power vector of the DC line, B s is the inverse matrix of the constant matrix related to the network topology and line resistance, V is the vector of the square of the DC node voltage amplitude, V ui_D and V li_D are the upper and lower limits of the voltage at node i respectively.

[0033] The technical solution adopted by the present invention to solve its technical problem is: to provide an electronic device, including a memory, a processor and a computer program stored in the memory and executable on the processor, wherein the processor implements the steps of the above-mentioned flexible interconnected distribution network optimization operation method when executing the computer program.

[0034] The technical solution adopted by the present invention to solve its technical problem is: providing a computer-readable storage medium on which a computer program is stored, and when the computer program is executed by a processor, the steps of the above-mentioned flexible interconnected distribution network optimization operation method are implemented.

[0035] Beneficial Effects

[0036] Due to the adoption of the above technical solution, the present invention has the following advantages and positive effects compared with the prior art: the present invention forms a unified DC model by establishing approximate linear power flow equations for the AC part and the DC part in the AC / DC distribution network, and uses the unified DC model as a constraint for the optimal operation of the flexible interconnected distribution network, thereby converting the original nonlinear non-convex optimization model into an approximate mixed integer linear programming model, avoiding cone relaxation of large-scale nonlinear constraints, and having no convergence problems, while improving the computational efficiency of the optimization algorithm. The present invention makes up for the shortcomings of other current methods for optimizing the operation of flexible interconnected devices, is conducive to a more comprehensive and in-depth exploration of the role of flexible interconnected devices in the distribution network, improves the flexibility of the distribution system, improves the quality of power, and provides a reliable reference for subsequent upgrades and renovations of the distribution network. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 is a flow chart of a method for optimizing operation of a flexible interconnected distribution network according to a first embodiment of the present invention;

[0038] Figure 2 It is a topological diagram of the AC / DC flexible interconnected distribution network in the first embodiment of the present invention. DETAILED DESCRIPTION

[0039] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall within the scope limited by the appended claims of the application equally.

[0040] The first embodiment of the present invention relates to a method for optimizing operation of a flexible interconnected distribution network, which can be applied to Figure 2 The AC / DC flexible interconnected distribution network shown in the figure first has a DC power flow model for the AC part and a DC power flow model for the DC part respectively; secondly, the DC power flow model for the AC part and the DC power flow model for the DC part are used as constraints for the optimal operation model of the flexible interconnected distribution network, so that the original nonlinear non-convex optimization configuration model can be transformed into an approximate mixed integer linear programming model, thereby avoiding cone relaxation of large-scale nonlinear constraints and improving the solution efficiency and accuracy.

[0041] like Figure 1 As shown, the flexible interconnected distribution network optimization operation method of this embodiment specifically includes the following steps:

[0042] Step 1: Approximately linearize the nonlinear power flow calculation equation of the AC part of the AC / DC distribution network and construct a DC power flow model of the AC part.

[0043] In this step, for the radial medium and low voltage AC distribution network, according to the active power and reactive power of each branch of the distribution network, the voltage phase of each node can be calculated by back substitution through the following linear equation:

[0044]

[0045] Among them, P ij and Q ij are the active power and reactive power flowing through the branch respectively; θ i and θ j are the voltage phase angles of node i and node j respectively, θ0 is the source node phase angle; r ij and x ij are the resistance and reactance of branch ij respectively.

[0046] In addition, the voltage at node i and the system admittance matrix are expressed as follows:

[0047]

[0048] Among them, V i b is the voltage amplitude reference value of node i, ΔV i is the correction value of the voltage amplitude reference value of node i; θ is the N-order phase angle difference matrix, in which the elements N-order square matrix Y + Internal elements y ij is the system admittance matrix coefficient.

[0049] Substituting the above equation into the conventional power flow equation of the distribution network and ignoring the second-order small quantity, the following equation can be obtained:

[0050]

[0051] Among them, V b is the node voltage amplitude reference value vector, ΔV is the node voltage amplitude reference value vector correction value vector; S is the node injection power vector, ΔS is the node injection power correction value vector. And because diag[Y + ·V b ]·ΔV=diag[ΔV]·Y + ·V b , substituting into the above formula, we can get the DC power flow model of the AC part:

[0052] ΔS=A s ΔV;

[0053] In the formula, A s =diag[Y + V b ]+diag[V b ]Y + The real part of the above node voltage correction is taken as the correction amount of the actual voltage, so as to obtain the amplitude and phase of the voltage of each node in the distribution network.

[0054] Step 2: Approximately linearize the nonlinear power flow calculation equation of the DC part of the AC / DC distribution network and construct a DC power flow model of the DC part.

[0055] According to the injected power of each node in the DC distribution network and the topological structure of the distribution network, the active power of each DC branch can be calculated by the following formula, ignoring the active and reactive network losses of the line:

[0056]

[0057] Where: P ij is the active power flowing through the branch; P jjis the injected active power of node j; k∈j means node k is one of the child nodes of node j. Then the active power of each branch can be recursively calculated according to the above formula. Based on the active power distribution of the branch, the voltage amplitude of each node can be calculated by back substitution through the following equation:

[0058]

[0059] Where: U i and U j Represent the voltage amplitude of node i and node j respectively; I ij Represents the current value flowing through branch ij; R ij is the resistance value of branch ij. U0 is the voltage amplitude of the DC grid source node, and its value is related to the DC port voltage reference value U ref Consistent.

[0060] In order to establish the DC power flow model, two intermediate variables are first introduced to replace the square terms in the above formula, and the second-order small quantities are ignored and converted into first-order terms, as shown in the following formula:

[0061]

[0062] In the formula, the intermediate variable V i and V j Represent the square of the voltage amplitude at node i and node j respectively. Finally, the DC branch power flow model of the DC distribution network is as follows:

[0063] P L =B s ·V;

[0064] Where: B s is a constant matrix related to network topology and line resistance, P L is the DC line active power vector, and V is the vector of the square of the DC node voltage amplitude.

[0065] Step 3, with the goal of minimizing the network loss of the flexible interconnected distribution network, and with the DC power flow model of the AC part and the DC power flow model of the DC part as constraints, an optimal operation model of the flexible interconnected distribution network is constructed.

[0066] Optimizing the power flow of AC and DC distribution networks using flexible interconnected switches is helpful to improve the economic efficiency of distribution network operation and the ability to accommodate new energy. However, the traditional power flow optimization model of AC and DC distribution networks is a non-convex nonlinear model. In order to improve the solution speed and convergence of the model, based on the DC branch power flow model of AC distribution network and the DC branch power flow model of DC distribution network mentioned above, the nonlinear constraints of the traditional optimization model are converted into approximate linear constraints.

[0067] The objective function of the flexible interconnected distribution network optimization operation model constructed in this step is:

[0068]

[0069] Among them, f is the objective function of the flexible interconnected distribution network optimization operation model, T is the number of daily sampling points in the optimization period, N L is the sum of the AC and DC distribution network lines, R ij is the resistance of branch ij, I ij,t is the effective value of the current in branch ij at time t, N SOP is the number of flexible interconnection switches connected to the distribution network, is the active power loss value of the i′th flexible interconnection switch at time t.

[0070] The constraints of the flexible interconnected distribution network optimization operation model constructed in this step include: flexible interconnected switch operation constraints, voltage source converter station operation constraints, line flow constraints based on the DC flow model of the AC part, node voltage constraints based on the DC flow model of the AC part, line flow constraints based on the DC flow model of the DC part, and node voltage constraints based on the DC flow model on the DC side.

[0071] The flexible interconnection switch SOP aims to replace the traditional feeder interconnection switch with a controllable power electronic converter, thereby realizing normalized flexible soft connection between feeders, and providing flexible, fast and accurate power exchange control and power flow optimization capabilities. This implementation method uses the back-to-back voltage source type SOP as the modeling object, and the SOP operation constraints are expressed as:

[0072]

[0073] in, is the active power transmitted by the flexible interconnection switch and the port connected to node i at time t, is the active power transmitted by the port connected to the flexible interconnection switch and node j at time t, is the active power loss value of the port connected to the flexible interconnection switch and node i at time t, is the active power loss value of the port connected to the flexible interconnection switch and node j at time t; is the converter loss coefficient of the flexible interconnection switch connected at node i, is the converter loss coefficient of the flexible interconnection switch connected at node j, is the reactive power transmitted by the flexible interconnection switch and the port connected to node i at time t, is the reactive power transmitted by the port connected to the flexible interconnection switch and node j at time t; i represents the operating state of the flexible interconnection switch connected to node i, σ j Indicates the operating state of the flexible interconnection switch connected to node j. It is a 0-1 variable. A value of 0 indicates that the SOP is not running. On the contrary, AN is the set of AC nodes in the AC / DC distribution network, N SOP is the number of flexible interconnection switches connected to the distribution network.

[0074] The voltage source converter station (VSC) is the connection point of the AC and DC lines. After ignoring the losses of the VSC itself, its simplified constraints include capacity constraints and line power constraints. Therefore, the VSC operation constraints are expressed as:

[0075]

[0076] Among them, S i,VSC represents the rated apparent power of the voltage source converter station at node i; and are the active power and reactive power injected into the AC side of the voltage source converter station at time t respectively; is the active power flowing out of the DC side of the voltage source converter station at time t; R i,VSC and X i,VSC are the equivalent resistance and reactance of the voltage source converter station at node i; V k,t and V i,t They represent the square of the effective value of the voltage at port k of the voltage source converter station and the square of the effective value of the voltage at node i at time t, respectively; i is an AC node, i∈A N , j is a DC node, j∈D N , k is the VSC AC port node.

[0077] The line power flow constraint of the DC power flow model based on the AC part is expressed as:

[0078]

[0079] Where P ji,t and Q ji,t They represent the active power and reactive power flowing through branch ij at time t respectively; B i is the set of child nodes of node i, i is the communication node, i∈A N ; and are the injected active power and reactive power of node i respectively; and are the active power of distributed renewable energy and load at node i at time t respectively; is the reactive power of the load on node i at time t. The other parameters are the same as above.

[0080] The node voltage constraint of the DC power flow model based on the AC part is expressed as:

[0081]

[0082] Among them, Vui_A and V li_A are the upper and lower limits of the voltage at node i respectively; and are the reference values ​​of the voltage amplitudes of nodes i and j respectively; ΔV i,t is the correction value of the voltage amplitude reference value of node i; ΔS i,t is the correction value of the power injected into node i; ΔS is the correction value vector of the power injected into the node, and ΔV is the correction value vector of the node voltage amplitude reference value vector. Matrix A s Determined by the system admittance matrix, The parameters and voltage values ​​in the above voltage constraints are calculated by approximating the DC power flow equation through the AC part.

[0083] The line power flow constraint of the DC power flow model based on the DC part is expressed as:

[0084]

[0085] Among them, P ji,t represents the power flowing through branch ij at time t; B i is the set of child nodes of node i, i is a DC node, i∈D N ; is the injected active power of node i. and are the active powers of distributed renewable energy and load at node i at time t respectively; the other parameters are the same as above.

[0086] The node voltage constraint based on the DC side DC power flow model is expressed as:

[0087]

[0088] Where V ui_D and V li_D are the upper and lower limits of the voltage at node i respectively; V i is the voltage amplitude of node i; V is the vector of the square of the DC node voltage amplitude, P L is the active power vector of the DC line. Matrix B s It is the inverse matrix of the constant matrix related to the network topology and line resistance, and is determined by the system admittance matrix. The parameters and voltage values ​​in the above voltage constraints are calculated by approximating the DC power flow equation in the DC part.

[0089] Step 4, solving the flexible interconnected distribution network optimization operation model to obtain the flexible interconnected distribution network optimization operation plan;

[0090] Step 5: Control the operation of the flexible interconnected distribution network according to the flexible interconnected distribution network optimization operation plan.

[0091] It is not difficult to find that the present invention forms a unified DC model by establishing approximate linear power flow equations of the AC part and the DC part in the AC / DC distribution network, and uses the unified DC model as a constraint for the optimized operation of the flexible interconnected distribution network, thereby converting the original nonlinear non-convex optimization model into an approximate mixed integer linear programming model, avoiding cone relaxation of large-scale nonlinear constraints, and having no convergence problems, while improving the computational efficiency of the optimization algorithm. The present invention makes up for the shortcomings of other current methods for optimizing the operation of flexible interconnected devices, is conducive to more comprehensive and in-depth exploration of the role of flexible interconnected devices in the distribution network, improves the flexibility of the distribution system, improves the quality of power, and provides a reliable reference for subsequent upgrades and renovations of the distribution network.

[0092] A second embodiment of the present invention relates to a flexible interconnected distribution network optimization operation device, comprising:

[0093] The AC part construction module is used to approximately linearize the nonlinear power flow calculation equation of the AC part of the AC / DC distribution network and construct a DC power flow model of the AC part;

[0094] A DC part construction module is used to approximately linearize the nonlinear power flow calculation equation of the DC part of the AC / DC distribution network and construct a DC power flow model of the DC part;

[0095] An operation model building module is used to build an optimized operation model of the flexible interconnected distribution network with the goal of minimizing the network loss of the flexible interconnected distribution network and with the DC power flow model of the AC part and the DC power flow model of the DC part as constraints;

[0096] A solution module, used for solving the flexible interconnected distribution network optimization operation model to obtain the flexible interconnected distribution network optimization operation plan;

[0097] A control module is used to control the operation of the flexible interconnected distribution network according to the flexible interconnected distribution network optimization operation plan.

[0098] The DC power flow model of the AC part constructed by the AC part construction module is expressed as: ΔS=A s ·ΔV, where ΔS is the node injection power correction vector, ΔV is the correction vector of the node voltage amplitude reference value vector, A s =diag[Y + V b ]+diag[V b ]Y + , V b is the node voltage amplitude reference value vector, Y + is the admittance matrix.

[0099] The DC power flow model of the DC part constructed by the DC part construction module is expressed as: L =B sV, where P L is the active power vector of the DC line, B s is a constant matrix related to the network topology and line resistance, and V is a vector of the square of the DC node voltage amplitude.

[0100] The objective function of the flexible interconnected distribution network optimization operation model constructed by the operation model construction module is: Among them, f is the objective function of the flexible interconnected distribution network optimization operation model, T is the number of daily sampling points in the optimization period, N L is the sum of the AC and DC distribution network lines, R ij is the resistance of branch ij, I ij,t is the effective value of the current in branch ij at time t, N SOP is the number of flexible interconnection switches connected to the distribution network, is the active power loss value of the i′th flexible interconnection switch at time t.

[0101] The constraints of the flexible interconnected distribution network optimization operation model constructed by the operation model construction module include: flexible interconnected switch operation constraints, voltage source converter station operation constraints, line flow constraints based on the DC flow model of the AC part, node voltage constraints based on the DC flow model of the AC part, line flow constraints based on the DC flow model of the DC part, and node voltage constraints based on the DC side DC flow model.

[0102] The flexible interconnection switch operation constraint is expressed as: in, is the active power transmitted by the flexible interconnection switch and the port connected to node i at time t, is the active power transmitted by the port connected to the flexible interconnection switch and node j at time t, is the active power loss value of the port connected to the flexible interconnection switch and node i at time t, is the active power loss value of the port connected to the flexible interconnection switch and node j at time t; is the converter loss coefficient of the flexible interconnection switch connected at node i, is the converter loss coefficient of the flexible interconnection switch connected at node j, is the reactive power transmitted by the flexible interconnection switch and the port connected to node i at time t, is the reactive power transmitted by the port connected to the flexible interconnection switch and node j at time t; i represents the operating state of the flexible interconnection switch connected to node i, σ j represents the operating status of the flexible interconnection switch connected to node j, A N is the set of AC nodes in the AC / DC distribution network, N SOP is the number of flexible interconnection switches connected to the distribution network.

[0103] The voltage source converter station operation constraints are expressed as: Among them, S i,VSC represents the rated apparent power of the voltage source converter station at node i; and are the active power and reactive power injected into the AC side of the voltage source converter station at time t respectively; is the active power flowing out of the DC side of the voltage source converter station at time t; R i,VSC and X i,VSC are the equivalent resistance and reactance of the voltage source converter station at node i; V k,t and V i,t They represent the square of the effective value of the voltage at port k of the voltage source converter station and the square of the effective value of the voltage at node i at time t respectively.

[0104] The line power flow constraint of the DC power flow model based on the AC part is expressed as: The node voltage constraint of the DC power flow model based on the AC part is expressed as: Among them, P ji,t and Q ji,t They represent the active power and reactive power flowing through branch ij at time t respectively; B i is the set of child nodes of node i, A N is the set of AC nodes in the AC / DC distribution network; and are the injected active power and reactive power of node i respectively; and are the active power of distributed renewable energy and load at node i at time t, is the active power transmitted by the flexible interconnection switch and the port connected to node i at time t, is the reactive power transmitted by the flexible interconnection switch and the port connected to node i at time t, and are the active power and reactive power injected into the AC side of the voltage source converter station at time t respectively; is the reactive power of the load on node i at time t; ΔS is the node injection power correction vector, ΔV is the correction vector of the node voltage amplitude reference value vector, V b is the node voltage amplitude reference value vector, Y + is the admittance matrix; ΔS i,t is the correction amount of the power injected into node i, and are the reference values ​​of the voltage amplitudes of nodes i and j respectively; is the element of the admittance matrix, V ui_A and Vli_A are the upper and lower limits of the voltage at node i, ΔV i,t is the correction value of the voltage amplitude reference value of node i.

[0105] The line power flow constraint of the DC power flow model based on the DC part is expressed as: The node voltage constraint based on the DC side DC power flow model is expressed as: Among them, P ji,t represents the power flowing through branch ij at time t; B i is the set of child nodes of node i, D N is the set of DC nodes in the AC / DC distribution network, is the injected active power of node i; and are the active power of distributed renewable energy and load at node i at time t, is the active power flowing out of the DC side of the voltage source converter station at time t; P L is the active power vector of the DC line, B s is the inverse matrix of the constant matrix related to the network topology and line resistance, V is the vector of the square of the DC node voltage amplitude, V ui_D and V li_D are the upper and lower limits of the voltage at node i respectively.

[0106] A third embodiment of the present invention relates to an electronic device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor implements the steps of the method for optimizing operation of a flexible interconnected distribution network of the first embodiment when executing the computer program.

[0107] The fourth embodiment of the present invention relates to a computer-readable storage medium having a computer program stored thereon, and when the computer program is executed by a processor, the steps of the method for optimizing operation of a flexible interconnected distribution network of the first embodiment are implemented.

[0108] Those skilled in the art will appreciate that the embodiments of the present application may be provided as methods, systems, or computer program products. Therefore, the present application may adopt the form of a complete hardware embodiment, a complete software embodiment, or an embodiment in combination with software and hardware. Moreover, the present application may adopt the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage and optical storage, etc.) that contain computer-usable program code.

[0109] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0110] These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing device to work in a specific manner, so that the instructions stored in the computer-readable memory produce a manufactured product including an instruction method, which is implemented in the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0111] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0112] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art can easily think of changes or substitutions within the technical scope disclosed by the present invention, which should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A method for optimizing operation of a flexible interconnected distribution network, characterized in that: The following steps are involved: The nonlinear power flow calculation equation of the AC part of the AC / DC distribution network is approximately linearized to construct a DC power flow model of the AC part; The nonlinear power flow calculation equation of the DC part of the AC / DC distribution network is approximately linearized to construct a DC power flow model of the DC part; With the goal of minimizing the network loss of the flexible interconnected distribution network, and with the DC power flow model of the AC part and the DC power flow model of the DC part as constraints, an optimal operation model of the flexible interconnected distribution network is constructed; Solving the optimal operation model of the flexible interconnected distribution network to obtain an optimal operation plan for the flexible interconnected distribution network; The flexible interconnected distribution network is controlled to operate according to the flexible interconnected distribution network optimization operation plan.

2. The method for optimizing operation of a flexible interconnected distribution network according to claim 1, characterized in that: The DC power flow model of the AC part is expressed as: ΔS = A s ·ΔV, where ΔS is the node injection power correction vector, ΔV is the correction vector of the node voltage amplitude reference value vector, A s =diag[Y + V b ]+diag[V b ]Y + , V b is the node voltage amplitude reference value vector, Y + is the admittance matrix.

3. The method for optimizing operation of a flexible interconnected distribution network according to claim 1, characterized in that: The DC power flow model of the DC part is expressed as: L =B s V, where P L is the active power vector of the DC line, B s is a constant matrix related to the network topology and line resistance, and V is a vector of the square of the DC node voltage amplitude.

4. The method for optimizing operation of a flexible interconnected distribution network according to claim 1, characterized in that: The objective function of the flexible interconnected distribution network optimization operation model is: Among them, f is the objective function of the flexible interconnected distribution network optimization operation model, T is the number of daily sampling points in the optimization period, N L is the sum of the AC and DC distribution network lines, R ij is the resistance of branch ij, I ij,t is the effective value of the current in branch ij at time t, N SOP is the number of flexible interconnection switches connected to the distribution network, is the active power loss value of the i′th flexible interconnection switch at time t.

5. The method for optimizing operation of a flexible interconnected distribution network according to claim 1, characterized in that: The constraint conditions of the flexible interconnected distribution network optimization operation model include: flexible interconnected switch operation constraints, voltage source converter station operation constraints, line flow constraints based on the DC flow model of the AC part, node voltage constraints based on the DC flow model of the AC part, line flow constraints based on the DC flow model of the DC part, and node voltage constraints based on the DC side DC flow model.

6. The method for optimizing operation of a flexible interconnected distribution network according to claim 5, characterized in that: The flexible interconnection switch operation constraint is expressed as: in, is the active power transmitted by the flexible interconnection switch and the port connected to node i at time t, is the active power transmitted by the port connected to the flexible interconnection switch and node j at time t, is the active power loss value of the port connected to the flexible interconnection switch and node i at time t, is the active power loss value of the port connected to the flexible interconnection switch and node j at time t; is the converter loss coefficient of the flexible interconnection switch connected at node i, is the converter loss coefficient of the flexible interconnection switch connected at node j, is the reactive power transmitted by the flexible interconnection switch and the port connected to node i at time t, is the reactive power transmitted by the port connected to the flexible interconnection switch and node j at time t; i represents the operating state of the flexible interconnection switch connected to node i, σ j represents the operating status of the flexible interconnection switch connected to node j, A N is the set of AC nodes in the AC / DC distribution network, N SOP is the number of flexible interconnection switches connected to the distribution network.

7. The method for optimizing operation of a flexible interconnected distribution network according to claim 5, characterized in that: The voltage source converter station operation constraints are expressed as: Among them, S i,VSC represents the rated apparent power of the voltage source converter station at node i; and are the active power and reactive power injected into the AC side of the voltage source converter station at time t respectively; is the active power flowing out of the DC side of the voltage source converter station at time t; R i,VSC and X i,VSC are the equivalent resistance and reactance of the voltage source converter station at node i; V k,t and V i,t They represent the square of the effective value of the voltage at port k of the voltage source converter station and the square of the effective value of the voltage at node i at time t respectively.

8. The method for optimizing operation of a flexible interconnected distribution network according to claim 5, characterized in that: The line power flow constraint of the DC power flow model based on the AC part is expressed as: The node voltage constraint of the DC power flow model based on the AC part is expressed as: Among them, P ji,t and Q ji,t They represent the active power and reactive power flowing through branch ij at time t respectively; B i is the set of child nodes of node i, A N is the set of AC nodes in the AC / DC distribution network; and are the injected active power and reactive power of node i respectively; and are the active power of distributed renewable energy and load at node i at time t, is the active power transmitted by the flexible interconnection switch and the port connected to node i at time t, is the reactive power transmitted by the flexible interconnection switch and the port connected to node i at time t, and are the active power and reactive power injected into the AC side of the voltage source converter station at time t respectively; is the reactive power of the load on node i at time t; ΔS is the node injection power correction vector, ΔV is the correction vector of the node voltage amplitude reference value vector, V b is the node voltage amplitude reference value vector, Y + is the admittance matrix; ΔS i,t is the correction amount of the power injected into node i, and are the reference values ​​of the voltage amplitudes of nodes i and j respectively; is the element of the admittance matrix, V ui_A and V li_A are the upper and lower limits of the voltage at node i, ΔV i,t is the correction value of the voltage amplitude reference value of node i.

9. The method for optimizing operation of a flexible interconnected distribution network according to claim 5, characterized in that: The line power flow constraint of the DC power flow model based on the DC part is expressed as: The node voltage constraint based on the DC side DC power flow model is expressed as: Among them, P ji,t represents the power flowing through branch ij at time t; B i is the set of child nodes of node i, D N is the set of DC nodes in the AC / DC distribution network, is the injected active power of node i; and are the active power of distributed renewable energy and load at node i at time t, is the active power flowing out of the DC side of the voltage source converter station at time t; P L is the active power vector of the DC line, B s is the inverse matrix of the constant matrix related to the network topology and line resistance, V is the vector of the square of the DC node voltage amplitude, V ui_D and V li_D are the upper and lower limits of the voltage at node i respectively.

10. A flexible interconnected distribution network optimization operation device, characterized in that: include: The AC part construction module is used to approximately linearize the nonlinear power flow calculation equation of the AC part of the AC / DC distribution network and construct a DC power flow model of the AC part; A DC part construction module is used to approximately linearize the nonlinear power flow calculation equation of the DC part of the AC / DC distribution network and construct a DC power flow model of the DC part; An operation model building module is used to build an optimized operation model of the flexible interconnected distribution network with the goal of minimizing the network loss of the flexible interconnected distribution network and with the DC power flow model of the AC part and the DC power flow model of the DC part as constraints; A solution module, used for solving the flexible interconnected distribution network optimization operation model to obtain the flexible interconnected distribution network optimization operation plan; A control module is used to control the operation of the flexible interconnected distribution network according to the flexible interconnected distribution network optimization operation plan.

11. The flexible interconnected distribution network optimization operation device according to claim 10, characterized in that: The DC power flow model of the AC part constructed by the AC part construction module is expressed as: ΔS=A s ·ΔV, where ΔS is the node injection power correction vector, ΔV is the correction vector of the node voltage amplitude reference value vector, A s =diag[Y + V b ]+diag[V b ]Y + , V b is the node voltage amplitude reference value vector, Y + is the admittance matrix.

12. The flexible interconnected distribution network optimization operation device according to claim 10, characterized in that: The DC power flow model of the DC part constructed by the DC part construction module is expressed as: L =B s V, where P L is the active power vector of the DC line, B s is a constant matrix related to the network topology and line resistance, and V is a vector of the square of the DC node voltage amplitude.

13. The flexible interconnected distribution network optimization operation device according to claim 10, characterized in that: The objective function of the flexible interconnected distribution network optimization operation model constructed by the operation model construction module is: Among them, f is the objective function of the flexible interconnected distribution network optimization operation model, T is the number of daily sampling points in the optimization period, N L is the sum of the AC and DC distribution network lines, R ij is the resistance of branch ij, I ij,t is the effective value of the current in branch ij at time t, N SOP is the number of flexible interconnection switches connected to the distribution network, is the active power loss value of the i′th flexible interconnection switch at time t.

14. The flexible interconnected distribution network optimization operation device according to claim 10, characterized in that: The constraints of the flexible interconnected distribution network optimization operation model constructed by the operation model construction module include: flexible interconnected switch operation constraints, voltage source converter station operation constraints, line flow constraints based on the DC flow model of the AC part, node voltage constraints based on the DC flow model of the AC part, line flow constraints based on the DC flow model of the DC part, and node voltage constraints based on the DC side DC flow model.

15. The flexible interconnected distribution network optimization operation device according to claim 14, characterized in that: The flexible interconnection switch operation constraint is expressed as: in, is the active power transmitted by the flexible interconnection switch and the port connected to node i at time t, is the active power transmitted by the port connected to the flexible interconnection switch and node j at time t, is the active power loss value of the port connected to the flexible interconnection switch and node i at time t, is the active power loss value of the port connected to the flexible interconnection switch and node j at time t; is the converter loss coefficient of the flexible interconnection switch connected at node i, is the converter loss coefficient of the flexible interconnection switch connected at node j, is the reactive power transmitted by the flexible interconnection switch and the port connected to node i at time t, is the reactive power transmitted by the port connected to the flexible interconnection switch and node j at time t; i represents the operating state of the flexible interconnection switch connected to node i, σ j represents the operating status of the flexible interconnection switch connected to node j, A N is the set of AC nodes in the AC / DC distribution network, N SOP is the number of flexible interconnection switches connected to the distribution network.

16. The flexible interconnected distribution network optimization operation device according to claim 14, characterized in that: The voltage source converter station operation constraints are expressed as: Among them, S i,VSC represents the rated apparent power of the voltage source converter station at node i; and are the active power and reactive power injected into the AC side of the voltage source converter station at time t respectively; is the active power flowing out of the DC side of the voltage source converter station at time t; R i,VSC and X i,VSC are the equivalent resistance and reactance of the voltage source converter station at node i; V k,t and V i,t They represent the square of the effective value of the voltage at port k of the voltage source converter station and the square of the effective value of the voltage at node i at time t respectively.

17. The flexible interconnected distribution network optimization operation device according to claim 14, characterized in that: The line power flow constraint of the DC power flow model based on the AC part is expressed as: The node voltage constraint of the DC power flow model based on the AC part is expressed as: Among them, P ji,t and Q ji,t They represent the active power and reactive power flowing through branch ij at time t respectively; B i is the set of child nodes of node i, A N is the set of AC nodes in the AC / DC distribution network; and are the injected active power and reactive power of node i respectively; and are the active power of distributed renewable energy and load at node i at time t, is the active power transmitted by the flexible interconnection switch and the port connected to node i at time t, is the reactive power transmitted by the flexible interconnection switch and the port connected to node i at time t, and are the active power and reactive power injected into the AC side of the voltage source converter station at time t respectively; is the reactive power of the load on node i at time t; ΔS is the node injection power correction vector, ΔV is the correction vector of the node voltage amplitude reference value vector, V b is the node voltage amplitude reference value vector, Y + is the admittance matrix; ΔS i,t is the correction amount of the power injected into node i, and are the reference values ​​of the voltage amplitudes of nodes i and j respectively; is the element of the admittance matrix, V ui_A and V li_A are the upper and lower limits of the voltage at node i, ΔV i,t is the correction value of the voltage amplitude reference value of node i.

18. The flexible interconnected distribution network optimization operation device according to claim 14, characterized in that: The line power flow constraint of the DC power flow model based on the DC part is expressed as: The node voltage constraint based on the DC side DC power flow model is expressed as: Among them, P ji,t represents the power flowing through branch ij at time t; B i is the set of child nodes of node i, D N is the set of DC nodes in the AC / DC distribution network, is the injected active power of node i; and are the active power of distributed renewable energy and load at node i at time t, is the active power flowing out of the DC side of the voltage source converter station at time t; P L is the active power vector of the DC line, B s is the inverse matrix of the constant matrix related to the network topology and line resistance, V is the vector of the square of the DC node voltage amplitude, V ui_D and V li_D are the upper and lower limits of the voltage at node i respectively.

19. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that: When the processor executes the computer program, the steps of the method for optimizing operation of a flexible interconnected distribution network as described in any one of claims 1 to 9 are implemented.

20. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the method for optimizing operation of a flexible interconnected distribution network as described in any one of claims 1 to 9 are implemented.

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