Load flow calculation method, system, equipment and medium

Abstract

The invention provides a load flow calculation method, system and device and a medium, and the method comprises the steps: obtaining a topology network state and operation parameters of a flexible DC power transmission system; by means of the Newton-Raphson method, the topology network state and the operation parameters are substituted into an alternating-current and direct-current power grid load flow calculation equation set for calculation, and node power and line power of the flexible direct-current power transmission system are obtained; the alternating-current and direct-current power grid load flow calculation equation set comprises a load flow calculation model of a direct-current power flow controller in the flexible direct-current power transmission system and a load flow calculation model of a direct-current transformer. According to the method, the calculation speed and the calculation efficiency of load flow calculation can be ensured while the load flow calculation precision is ensured.

Description

Technical Field

[0001] The present invention relates to the field of power systems, and in particular to a power flow calculation method, system, equipment and medium. Background Art

[0002] DC grid technology based on flexible direct current transmission (HVDC) is considered the most effective solution for integrating large-scale distributed renewable energy, powering ocean archipelagos, centralized transmission from offshore wind farm clusters, and building new urban power grids. It has become a hot topic of research in the international power sector. The technology and construction of HVDC networks have become a key development direction and component of future power grids.

[0003] Research on DC grids has already begun in earnest abroad, encompassing all aspects of the network. Many countries are also determining their DC grid construction goals, action plans, and investment plans. These countries are also developing targeted DC grid plans tailored to their respective regulatory mechanisms, grid infrastructure, and social development.

[0004] In addition to AC / DC converters, future complex DC grids will include a variety of DC equipment, including DC transformers and DC power flow controllers, to provide steady-state control functions and achieve greater flexibility and diversity. Therefore, conducting power flow calculations for future complex DC grids is a pressing technical challenge, particularly in order to provide reasonable steady-state operating points for studying the system dynamic and transient performance of future DC grids and to address various issues arising from their system planning and operation. Summary of the Invention

[0005] In order to solve the problems of the prior art, the present invention proposes a power flow calculation method, system, device and medium, which aim to ensure the accuracy of power flow calculation while ensuring the calculation speed and efficiency of power flow calculation.

[0006] The purpose of the present invention is achieved by adopting the following technical solutions:

[0007] In one aspect, an embodiment of the present invention provides a power flow calculation method applicable to a flexible direct current transmission system, the method comprising:

[0008] Obtain the topological network status and operating parameters of the flexible DC transmission system;

[0009] The topological network state and the operating parameters are substituted into a set of AC and DC power grid flow calculation equations using the Newton-Raphson method to perform calculations to obtain the node power and line power of the flexible DC transmission system; the set of AC and DC power grid flow calculation equations includes a flow calculation model of the DC transformer in a flow calculation model of the DC power flow controller in the flexible DC transmission system.

[0010] Optionally, the process of constructing the AC / DC power grid power flow calculation equation set includes:

[0011] Analyzing the voltage-current relationship of each node in the flexible direct current transmission system to obtain an AC / DC power flow equation set consisting of power flow calculation equations for each node;

[0012] By adopting a voltage control variable method, a power flow calculation model of the DC power flow controller and a power flow calculation model of the DC transformer in the flexible DC power transmission system are respectively established;

[0013] The power flow calculation model of the DC power flow controller and the power flow calculation model of the DC transformer are added to the AC / DC power flow equation set to obtain the AC / DC power grid power flow calculation equation set.

[0014] Optionally, the method of adopting voltage control variables to establish a power flow calculation model of the DC power flow controller and a power flow calculation model of the DC transformer in the flexible DC power transmission system includes:

[0015] By adopting the voltage control variable method, the voltage of the DC node connected to the DC power flow controller and the superimposed DC voltage generated by the DC power flow controller are analyzed to obtain a power flow calculation model of the DC power flow controller;

[0016] The voltage of a DC node connected to the DC transformer, the ideal transformation ratio of the DC transformer, and the equivalent series conductance of the DC transformer are analyzed to obtain a power flow calculation model of the DC transformer.

[0017] Optionally, the DC power flow controller includes a single-branch DC power flow controller; the DC nodes connected to the DC power flow controller include node a and node b; and a power flow calculation model of the DC power flow controller satisfies the following formula:

[0018]

[0019] Among them, U DCa is the voltage of the node a; U DCb is the voltage of the node b; U p1 Y is the superimposed DC voltage generated by the single-branch DC power flow controller; ab is the conductance between the node a and the node b; ab is the control DC current target value of the single-branch DC power flow controller; P DCa is the power value of the node a; U DCi is the voltage of the i-th DC node connected to the node a; Y aiis the conductance between the node a and the ith DC node connected to it; P DCb is the power value of the node b; U DCj is the voltage of the jth DC node connected to the node b; Y bj is the conductance between the node b and the j-th DC node connected to it.

[0020] Optionally, the DC power flow controller includes: a dual-branch DC power flow controller; the dual branches are: a first branch including nodes c and d, and a second branch including nodes c and e; the power flow calculation model of the DC power flow controller satisfies the following formula:

[0021]

[0022] Among them, U DCc is the voltage of the node c; U DCd is the voltage of the node d; U p2 Y is the superimposed DC voltage generated by the dual-branch DC power flow controller on the first branch; cd is the conductance between the node c and the node d; I cd is the target value of the DC current controlled by the dual-branch DC power flow controller on the first branch; U DCe is the voltage of the node e; U p3 Y is the superimposed DC voltage generated by the dual-branch DC power flow controller on the second branch; ce is the conductance between the node c and the node e; I ce I is the target value of the DC current controlled by the dual-branch DC power flow controller on the second branch; set is the DC transfer control target value of the dual-branch DC power flow controller; P DCc is the power value of the node c; U DCm is the voltage of the mth DC node connected to the node c; Y cm is the conductance between the node c and the mth DC node connected to it; P DCd is the power value of the node d; U DCn is the voltage of the nth DC node connected to the node d; Y dn is the conductance between the node d and the nth DC node connected to it; P DCe is the power value of the node e; U DCl is the voltage of the lth DC node connected to the node e; Y el is the conductance between the node e and the lth DC node connected to it.

[0023] Optionally, the DC nodes connected to the DC transformer include: node f and node g; the power flow calculation model of the DC transformer satisfies the following formula:

[0024]

[0025] Among them, P DCf is the power value of the node f; U DCf is the voltage of the node f; U DCo is the voltage of the oth DC node connected to the node f; Y fo is the conductance between the node f and the oth DC node connected to it; U DCg is the voltage of the node g; T q is the ideal transformation ratio of the DC transformer; G q is the equivalent series conductance of the DC transformer; P DCg is the power value of the node g; U DCg is the voltage of the node g; U DCp is the voltage of the pth DC node connected to the node g; Y gp is the conductance between the node g and the pth DC node connected to it.

[0026] Optionally, before adding the power flow calculation model of the DC power flow controller and the power flow calculation model of the DC transformer to the AC / DC power flow equation set to obtain the AC / DC power grid power flow calculation equation set, the method further includes:

[0027] Based on the power conservation principle of the AC / DC converter in the flexible DC power transmission system, a power flow calculation model of the AC / DC converter is established;

[0028] The power flow calculation model of the DC power flow controller and the power flow calculation model of the DC transformer are added to the AC / DC power flow equation set to obtain the AC / DC power grid power flow calculation equation set, including:

[0029] The power flow calculation model of the DC power flow controller, the power flow calculation model of the DC transformer, and the power flow calculation model of the AC / DC converter are simultaneously added to the AC / DC power flow equation set to obtain the AC / DC power grid power flow calculation equation set.

[0030] Optionally, establishing a power flow calculation model of the AC / DC converter based on the power conservation principle of the AC / DC converter in the flexible HVDC power transmission system includes:

[0031] Based on the power conservation principle of the AC / DC converter, constructing an AC / DC correlation equation and an AC / DC power correlation equation in the AC / DC converter;

[0032] Constructing a power control equation for the AC / DC converter in an active power control mode, and a power control equation for the AC / DC converter in a reactive power control mode;

[0033] Based on the AC / DC correlation equation, the AC / DC power correlation equation, the power control equation under the active power control mode, and the power control equation under the reactive power control mode, a power flow calculation model of the AC / DC converter is constructed.

[0034] On the other hand, the present invention further provides a power flow calculation system applicable to a flexible direct current transmission system, the system comprising:

[0035] An acquisition module is used to obtain the topological network status and operating parameters of the flexible DC transmission system;

[0036] A calculation module is configured to substitute the topological network state and the operating parameters into a set of AC and DC power grid flow calculation equations using a Newton-Raphson method to perform calculations, thereby obtaining a node power and a line power of the flexible DC transmission system; the set of AC and DC power grid flow calculation equations includes a flow calculation model of a DC power flow controller and a flow calculation model of a DC transformer in the flexible DC transmission system.

[0037] Optionally, the system further includes:

[0038] an analysis module, configured to analyze the voltage-current relationship of each node in the flexible DC power transmission system to obtain a set of AC and DC power flow equations consisting of power flow calculation equations for each node;

[0039] A first establishing module is configured to establish a power flow calculation model of the DC power flow controller and a power flow calculation model of the DC transformer in the flexible DC power transmission system respectively by adopting a voltage control variable method;

[0040] A supplementing module is used to supplement the power flow calculation model of the DC power flow controller and the power flow calculation model of the DC transformer into the AC / DC power flow equation set to obtain the AC / DC power grid power flow calculation equation set.

[0041] Optionally, the first establishment module is specifically used to analyze the voltage of the DC node connected to the DC power flow controller and the superimposed DC voltage generated by the DC power flow controller by adopting the voltage control variable method to obtain the power flow calculation model of the DC power flow controller; and analyze the voltage of the DC node connected to the DC transformer, the ideal transformation ratio of the DC transformer and the equivalent series conductance of the DC transformer to obtain the power flow calculation model of the DC transformer.

[0042] Optionally, the DC power flow controller includes a single-branch DC power flow controller; the DC nodes connected to the DC power flow controller include node a and node b; and a power flow calculation model of the DC power flow controller satisfies the following formula:

[0043]

[0044] Among them, U DCa is the voltage of the node a; U DCb is the voltage of the node b; U p1 Y is the superimposed DC voltage generated by the single-branch DC power flow controller; ab is the conductance between the node a and the node b; ab is the control DC current target value of the single-branch DC power flow controller; P DCa is the power value of the node a; U DCi is the voltage of the i-th DC node connected to the node a; Y ai is the conductance between the node a and the ith DC node connected to it; P DCb is the power value of the node b; U DCj is the voltage of the jth DC node connected to the node b; Y bj is the conductance between the node b and the j-th DC node connected to it.

[0045] Optionally, the DC power flow controller includes: a dual-branch DC power flow controller; the dual branches are: a first branch including nodes c and d, and a second branch including nodes c and e; the power flow calculation model of the DC power flow controller satisfies the following formula:

[0046]

[0047] Among them, U DCc is the voltage of the node c; U DCd is the voltage of the node d; U p2 Y is the superimposed DC voltage generated by the dual-branch DC power flow controller on the first branch; cd is the conductance between the node c and the node d; I cd is the target value of the DC current controlled by the dual-branch DC power flow controller on the first branch; U DCe is the voltage of the node e; U p3 Y is the superimposed DC voltage generated by the dual-branch DC power flow controller on the second branch; ce is the conductance between the node c and the node e; I ce I is the target value of the DC current controlled by the dual-branch DC power flow controller on the second branch;set is the DC transfer control target value of the dual-branch DC power flow controller; P DCc is the power value of the node c; U DCm is the voltage of the mth DC node connected to the node c; Y cm is the conductance between the node c and the mth DC node connected to it; P DCd is the power value of the node d; U DCn is the voltage of the nth DC node connected to the node d; Y dn is the conductance between the node d and the nth DC node connected to it; P DCe is the power value of the node e; U DCl is the voltage of the lth DC node connected to the node e; Y el is the conductance between the node e and the lth DC node connected to it.

[0048] Optionally, the DC nodes connected to the DC transformer include: node f and node g; the power flow calculation model of the DC transformer satisfies the following formula:

[0049]

[0050] Among them, P DCf is the power value of the node f; U DCf is the voltage of the node f; U DCo is the voltage of the oth DC node connected to the node f; Y fo is the conductance between the node f and the oth DC node connected to it; U DCg is the voltage of the node g; T q is the ideal transformation ratio of the DC transformer; G q is the equivalent series conductance of the DC transformer; P DCg is the power value of the node g; U DCg is the voltage of the node g; U DCp is the voltage of the pth DC node connected to the node g; Y gp is the conductance between the node g and the pth DC node connected to it.

[0051] Optionally, the system further includes: a second establishing module, configured to establish a power flow calculation model of the AC / DC converter based on a power conservation principle of the AC / DC converter in the flexible DC power transmission system;

[0052] Correspondingly, the supplementing module is further used to simultaneously supplement the power flow calculation model of the DC power flow controller, the power flow calculation model of the DC transformer, and the power flow calculation model of the AC / DC converter to the AC / DC power flow equation set to obtain the AC / DC power grid power flow calculation equation set.

[0053] Optionally, the second establishment module is specifically used to construct the AC / DC correlation equation and the AC / DC power correlation equation in the AC / DC converter based on the power conservation principle of the AC / DC converter; construct the power control equation of the AC / DC converter under the active power control mode, and the power control equation of the AC / DC converter under the reactive power control mode; based on the AC / DC correlation equation, the AC / DC power correlation equation, the power control equation under the active power control mode, and the power control equation under the reactive power control mode, construct a power flow calculation model of the AC / DC converter.

[0054] In another aspect, an embodiment of the present invention further provides an electronic device, comprising: at least one processor and a memory; the memory and the processor are connected via a bus;

[0055] The memory is used to store one or more programs;

[0056] When the one or more programs are executed by the at least one processor, the power flow calculation method applicable to a flexible direct current transmission system as described in any one of the above items is implemented.

[0057] Correspondingly, an embodiment of the present invention further provides a readable storage medium having an execution program stored thereon. When the execution program is executed, the power flow calculation method applicable to a flexible direct current transmission system as described above is implemented.

[0058] Compared with the prior art, the present invention has the following beneficial effects:

[0059] The present invention provides a power flow calculation method, system, device, and medium. During the execution of the method, the topological network state and operating parameters of a flexible direct current (HVDC) transmission system are first obtained. Then, using the Newton-Raphson method, the topological network state and operating parameters are substituted into a set of AC / DC power flow calculation equations for calculation to obtain the node power and line power of the flexible HVDC transmission system. The AC / DC power flow calculation equations include a power flow calculation model for a DC power flow controller and a power flow calculation model for a DC transformer in the flexible HVDC transmission system. This method avoids the impact of the DC power flow controller and DC transformer on branch power flows, thereby ensuring that the number of nodes in the flexible HVDC transmission system remains unchanged. Specifically, the order and elements of the node admittance matrix and Jacobian matrix in the flexible HVDC transmission system remain unchanged. This effectively avoids the increased computational complexity and amount of computation in conventional power flow calculation methods, thereby ensuring both the accuracy of the power flow calculation and the speed and efficiency of the power flow calculation.

[0060] It should be understood that the above general description and the following detailed description are merely exemplary and explanatory, and are not intended to limit the technical solutions provided by the embodiments of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0061] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. Those skilled in the art can also derive other drawings based on these drawings without inventive work, among which:

[0062] Figure 1 A flow chart of a power flow calculation method applicable to a flexible direct current transmission system provided by an embodiment of the present invention;

[0063] Figure 2 A schematic diagram of the AC / DC power grid flow calculation process corresponding to a flexible DC transmission system provided in an embodiment of the present invention;

[0064] Figure 3 A schematic diagram of a system power flow calculation result obtained by applying a power flow calculation method for a flexible HVDC system provided by an embodiment of the present invention;

[0065] Figure 4 A schematic diagram of the composition of a power flow calculation system applicable to a flexible direct current transmission system provided by an embodiment of the present invention;

[0066] Figure 5 A schematic diagram of the composition of an electronic device provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0067] The following describes the embodiments of the present invention with reference to the accompanying drawings and preferred embodiments. Those skilled in the art will readily appreciate the other advantages and benefits of the present invention from the disclosure herein. The present invention may also be implemented or applied through various other specific embodiments, and the various details in this specification may be modified or altered based on different viewpoints and applications without departing from the spirit of the present invention. It should be understood that the preferred embodiments are intended only to illustrate the present invention and are not intended to limit the scope of protection of the present invention.

[0068] In the following description, reference is made to “some embodiments”, which describes a subset of all possible embodiments, but it will be understood that “some embodiments” may be the same subset or different subsets of all possible embodiments and may be combined with each other without conflict.

[0069] In the following description, the terms "first\second\third" are merely used to distinguish similar objects and do not represent a specific ordering of the objects. It is understandable that "first\second\third" can be interchanged with a specific order or sequence where permitted, so that the embodiments of the present invention described herein can be implemented in an order other than that illustrated or described herein.

[0070] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art in the art of the embodiments of the present invention. The terms used herein are only for the purpose of describing the embodiments of the present invention and are not intended to limit the embodiments of the present invention.

[0071] Example 1

[0072] The present invention provides a method for calculating power flow in a flexible DC transmission system. Figure 1 As shown, the method includes the following steps:

[0073] Step 101: Obtain the topological network status and operating parameters of the flexible DC transmission system.

[0074] In some embodiments of the present invention, a flexible direct current transmission system is a high-voltage direct current transmission technology based on a voltage source converter (VSC) or a modular multilevel converter (MMC). The core of the system is to achieve independent control of active and reactive power through fully controlled power devices, such as insulated-gate bipolar transistors (IGBTs) and integrated gate-commutated thyristors (IGCTs), thereby improving the flexibility and stability of the power grid.

[0075] The topological network state of the HVDC Flexible system can include end-to-end, back-to-back, and multi-terminal, depending on the application scenario and functional requirements. Furthermore, the operating parameters of the HVDC Flexible system primarily include the voltage, power, and control mode of each node and device in the HVDC Flexible system. The topological network state and operating parameters of the HVDC Flexible system jointly determine its ability to adapt to complex grid requirements.

[0076] Step 102: Using the Newton-Raphson method, substitute the topological network state and the operating parameters into AC / DC power grid power flow calculation equations to perform centralized calculations to obtain the node power and line power of the flexible DC transmission system.

[0077] The AC / DC power grid power flow calculation equation set includes: a power flow calculation model of a DC power flow controller in the flexible DC power transmission system and a power flow calculation model of a DC transformer.

[0078] In some embodiments of the present invention, the Newton-Raphson method is also known as Newton's method, which is a method for approximately solving equations in the real number field and the complex number field. The method uses the first few terms of the Taylor series of the function f(x) to find the roots of the equation f(x)=0.

[0079] In some embodiments of the present invention, the corresponding power flow calculation can be performed using the Newton-Raphson method. That is, the topological network state and operating parameters of the flexible DC transmission system are substituted into the AC / DC power flow calculation equations, which include at least the power flow calculation model of the DC power flow controller and the power flow calculation model of the DC transformer in the flexible DC transmission system, to obtain the node power and line power of the flexible DC transmission system. The corresponding entire power flow calculation process can be found in [1]. Figure 2 As shown:

[0080] 201. Input Data. This involves inputting data into the AC / DC power flow calculation equations. This data may include: the topological network status of the HVDC Flexible system; known AC node types within the HVDC Flexible system; AC node voltage amplitude, phase, and power; DC node voltage and power; parameters of various DC device controllers; AC / DC line parameters; and AC transformer parameters.

[0081] 202. Correcting the node injection power based on the equivalent injection power method, that is, establishing a mathematical model describing the relationship between voltage, current and power in the flexible direct current transmission system based on the circuit theory and power system network model of the flexible direct current transmission system, which corresponds to the set of AC and DC power grid flow calculation equations mentioned in the embodiments of the present invention.

[0082] 203. Form a system node parameter matrix, that is, based on the grid structure and parameters of the flexible DC transmission system and the set of AC and DC grid power flow calculation equations mentioned in the embodiments of the present invention, form a node admittance matrix to describe the electrical connections between the nodes in the flexible DC transmission system.

[0083] 204. Set the node voltage initial value, that is, according to the actual situation of the flexible direct current transmission system, set the variable to be calculated, such as: set an initial value for the node voltage in the flexible direct current transmission system.

[0084] 205. Write the power equation and solve the power imbalance ΔP. That is, use the iterative method to solve the mathematical model built according to 201 to 204, and gradually update the values of the state variables until the convergence conditions are met.

[0085] 206. Determine if MaxΔP < ε, i.e., calculate MaxΔP based on the result of the iterative solution; wherein MaxΔP refers to the maximum value of the power imbalance of all nodes in the flexible DC transmission system, and ε is a preset value.

[0086] 207. If MaxΔP<ε, that is, the result of determination 206 is yes, then calculate the node power and line current values in the flexible DC transmission system.

[0087] 208. If MaxΔP ≥ ε, that is, the result of judgment 206 is no, then the Jacobian matrix J is formed to solve the voltage correction amount ΔU.

[0088] 209. Calculate the new voltage value U (i+1) =U (i) +ΔU, and execute step 205 again to recalculate; where U (i) and U (i+1) They are the node voltage at the i-th time and the node voltage at the i+1-th time respectively.

[0089] It should be noted that the set of AC / DC power grid power flow calculation equations, which at least includes the power flow calculation model of the DC power flow controller and the power flow calculation model of the DC transformer in the flexible DC transmission system, can be a pre-built complete set of AC / DC power grid power flow calculation equations containing multiple types of DC equipment. In addition to including: the power flow calculation model of the DC power flow controller and the power flow calculation model of the DC transformer in the flexible DC transmission system, it can also include: the power flow calculation model of the AC / DC converter in the flexible DC transmission system, the power flow calculation equations of each node (including all AC nodes and all DC nodes) in the flexible DC transmission system, etc.

[0090] In some embodiments of the present invention, the process of constructing the AC / DC power grid power flow calculation equation set can be implemented by following steps A1 to A3:

[0091] Step A1: Analyze the voltage-current relationship of each node in the flexible direct current transmission system to obtain an AC / DC power flow equation set consisting of power flow calculation equations of each node.

[0092] In some embodiments of the present invention, the voltage-current relationship at each node in the flexible DC transmission system is analyzed to construct (obtain) a power flow calculation equation for each node, thereby obtaining a set of AC and DC power flow equations consisting of the power flow calculation equations for multiple nodes. Here, a rectangular coordinate system power flow calculation equation is established that includes all AC nodes and all DC nodes in the flexible DC transmission system. The corresponding specific implementation steps can be referred to as the following process:

[0093] Firstly, the voltage and injected current of each node in the flexible DC transmission system are obtained in rectangular coordinate form.

[0094] Then, according to Kirchhoff's voltage law, the voltage and injected current of each node in the flexible DC transmission system are analyzed, and the voltage flow calculation equation and power flow calculation equation of each node in the flexible DC transmission system are obtained.

[0095] Finally, based on the voltage flow calculation equations and power flow calculation equations of each node in the flexible DC transmission system, the AC and DC flow equation set is constructed.

[0096] In some embodiments of the present invention, rectangular coordinates can be used to take the voltage and injected current of each node (including AC nodes and DC nodes) in the flexible DC transmission system as calculation variables to obtain a linear node voltage equation and a quadratic node power flow calculation equation.

[0097] Here, the power flow calculation equation of the AC node can refer to the following formula (1):

[0098]

[0099] in, is the complex phasor of the AC node voltage in rectangular coordinates; is the complex phasor of the AC node current in rectangular coordinates; Y AC is the admittance matrix of the AC node.

[0100] At the same time, for the i-th AC node in the flexible DC transmission system, its corresponding power equation can refer to the following formula (2):

[0101]

[0102] in, and are the voltage phasor and current phasor of the ith AC node, P ACiRefers to the power of the i-th AC node; jQ ACi Refers to the complex imaginary part of the phasor corresponding to the power of the i-th AC node.

[0103] Correspondingly, the power flow calculation equation of the DC node in the flexible DC transmission system can refer to the following formula (3):

[0104] Y DC *U DC =I DC Formula (3);

[0105] Among them, Y DC is the DC node conductance matrix; U DC is the DC node voltage vector; I DC is the DC node current phasor.

[0106] At the same time, for any m-th DC node in the flexible DC transmission system, the corresponding power equation can be referred to as shown in the following formula (4):

[0107] U DCm *I DCm =P DCm Formula (4);

[0108] Among them, U DCm and I DCm They are: the voltage and current of the mth AC node; P DCm is the active power of the mth DC node.

[0109] In some embodiments of the present invention, the basic structures of the AC and DC power flow equations corresponding to formulas (1) to (4) can be combined to obtain a set of AC and DC power flow equations consisting of power flow calculation equations for each node in the flexible DC transmission system.

[0110] Step A2: using a voltage control variable method, respectively establishing a power flow calculation model of the DC power flow controller and a power flow calculation model of the DC transformer in the flexible DC power transmission system.

[0111] In some embodiments of the present invention, a voltage-controlled variable approach, based on the principle of a single variable (e.g., voltage), analyzes the relationship between the corresponding factors and the research question to obtain corresponding conclusions or laws. In other words, the voltage-controlled variable approach, analyzing voltage as a single variable, is used to construct power flow calculation models for both the DC power flow controller and the DC transformer.

[0112] In some embodiments of the present invention, the above step A2 may be implemented with reference to the following steps A21 and A22:

[0113] Step A21: Analyze the voltage of the DC node connected to the DC power flow controller and the superimposed DC voltage generated by the DC power flow controller by using the voltage control variable to obtain a power flow calculation model of the DC power flow controller.

[0114] In some embodiments of the present invention, the DC power flow controller in the flexible DC power transmission system may include: a single-branch DC power flow controller and a dual-branch DC power flow controller.

[0115] It should be noted that by adopting the voltage control variable method, the voltage of the DC node connected to the DC power flow controller, the superimposed DC voltage generated on the branch formed by the DC power flow controller connected to the corresponding node, etc. can be analyzed to build a power equation of the DC node connected to the DC power flow controller, so that the power equation can be used as the power flow calculation model of the DC power flow controller.

[0116] In some embodiments of the present invention, taking the DC power flow controller in the flexible DC power transmission system as a single-branch DC power flow controller as an example, a power flow calculation model of the single-branch DC power flow controller is established based on the voltage control variable. The DC nodes connected to the DC power flow controller (i.e., the single-branch DC power flow controller) include: node a and node b. In other words, there is a single-branch DC power flow controller p1 between node a and node b in the flexible DC power transmission system. Accordingly, the power flow calculation model of the single-branch DC power flow controller p1 is established, and the relevant power equations of node a and node b can be generated. That is, the power flow calculation model of the single-branch DC power flow controller p1 can satisfy the following formula (5):

[0117]

[0118] Among them, U DCa is the voltage of the node a; U DCb is the voltage of the node b; U p1 Y is the superimposed DC voltage generated by the single-branch DC power flow controller; ab is the conductance between the node a and the node b; ab is the control DC current target value of the single-branch DC power flow controller; P DCa is the power value of the node a; U DCi is the voltage of the i-th DC node connected to the node a; Y ai is the conductance between the node a and the ith DC node connected to it; P DCb is the power value of the node b; U DCj is the voltage of the jth DC node connected to the node b; Y bj is the conductance between the node b and the j-th DC node connected to it.

[0119] It should be noted that P DCa and P DCb , which can also be described as: the power value between node a and node b after the single-branch DC power flow controller p1 is added between node a and node b.

[0120] In some embodiments of the present invention, taking the DC power flow controller in the flexible DC power transmission system as a dual-branch DC power flow controller as an example, a power flow calculation model of the dual-branch DC power flow controller is established based on the voltage control variable. Among them, the dual branches corresponding to the DC power flow controller (i.e., the dual-branch DC power flow controller) are: a first branch including nodes c and d, and a second branch including nodes c and e; in other words, the DC nodes connected to the dual-branch DC power flow controller include at least: nodes c, d, and e. Here, there is a dual-branch DC power flow controller p2 between nodes c, d, and e in the flexible DC power transmission system, and the power flow calculation model of the dual-branch DC power flow controller p2 is established accordingly, which can generate the relevant power equations of nodes c, d, and e, that is, the power flow calculation model of the single-branch DC power flow controller p2 can satisfy the following formula (6):

[0121]

[0122] Among them, U DCc is the voltage of the node c; U DCd is the voltage of the node d; U p2 Y is the superimposed DC voltage generated by the dual-branch DC power flow controller on the first branch; cd is the conductance between the node c and the node d; I cd is the target value of the DC current controlled by the dual-branch DC power flow controller on the first branch; U DCe is the voltage of the node e; U p3 Y is the superimposed DC voltage generated by the dual-branch DC power flow controller on the second branch; ce is the conductance between the node c and the node e; I ce I is the target value of the DC current controlled by the dual-branch DC power flow controller on the second branch; set is the DC transfer control target value of the dual-branch DC power flow controller; P DCc is the power value of the node c; U DCm is the voltage of the mth DC node connected to the node c; Y cm is the conductance between the node c and the mth DC node connected to it; P DCd is the power value of the node d; U DCnis the voltage of the nth DC node connected to the node d, Y dn is the conductance between the node d and the nth DC node connected to it; P DCe is the power value of the node e; U DCl is the voltage of the lth DC node connected to the node e; Y el is the conductance between the node e and the lth DC node connected to it.

[0123] It should be noted that P DCc 、P DCd and P DCe , can also be described as: after the dual-branch DC power flow controller p2 is added between nodes c, d and e, the power values of nodes c, d and e. At the same time, I set It can also be described as follows: after the dual-branch DC power flow controller p2 is added between nodes c, d, and e, the DC current transfer control target value on the first branch including nodes c and d, and the second branch including nodes c and e.

[0124] Step A22: Analyze the voltage of the DC node connected to the DC transformer, the ideal transformation ratio of the DC transformer, and the equivalent series conductance of the DC transformer to obtain a power flow calculation model of the DC transformer.

[0125] In some embodiments of the present invention, the voltage control variable method can continue to be used to analyze the voltage of the DC node connected to the DC transformer, the ideal transformation ratio of the DC transformer, and the equivalent series conductance of the DC transformer to build a power equation for the DC node connected to the DC transformer, thereby obtaining a power flow calculation model of the DC transformer.

[0126] In some embodiments of the present invention, the DC nodes connected to the DC transformer include: node f and node g; that is, a DC transformer q is provided between node f and node g; correspondingly, a power flow calculation model of the DC transformer q is established to generate relevant power equations for node f and node g, so that the power flow calculation model of the DC transformer q satisfies the following formula (7):

[0127]

[0128] Among them, P DCf is the power value of the node f, U DCf is the voltage at the node f, U DCo is the voltage of the oth DC node connected to the node f; Y fo is the conductance between the node f and the oth DC node connected to it; U DCg is the voltage of the node g, Tq is the ideal transformation ratio of the DC transformer; G q is the equivalent series conductance of the DC transformer; P DCg is the power value of the node g; U DCg is the voltage of the node g; U DCp is the voltage of the pth DC node connected to the node g; Y gp is the conductance between the node g and the pth DC node connected to it.

[0129] Step A3: Supplement the power flow calculation model of the DC power flow controller and the power flow calculation model of the DC transformer into the AC / DC power flow equation set to obtain the AC / DC power grid power flow calculation equation set.

[0130] In some embodiments of the present invention, the obtained power flow calculation model of the DC power flow controller (including: the power flow calculation model of the single-branch DC power flow controller and the power flow calculation model of the dual-branch DC power flow controller) and the power flow calculation model of the DC transformer are simultaneously supplemented to the AC and DC power flow equations obtained in step A1, that is, the above-mentioned formulas (1) to (7) are combined to obtain the AC and DC power grid power flow calculation equations.

[0131] In some embodiments of the present invention, before executing step A3, the following step B may be executed first:

[0132] Step B: Based on the power conservation principle of the AC / DC converter in the flexible HVDC power transmission system, a power flow calculation model of the AC / DC converter is established.

[0133] In some embodiments of the present invention, a corresponding power flow calculation model can be further constructed for the AC / DC converter in the flexible DC transmission system. Here, the power flow calculation model for the AC / DC converter can be established based on the power conservation principle of the AC / DC converter in the flexible DC transmission system.

[0134] It should be noted that the AC / DC converter must ensure power balance between the AC and DC sides while taking into account the AC / DC converter losses (such as switching losses and reactance losses).

[0135] In some embodiments of the present invention, step B may be implemented by the following process:

[0136] The first step is to construct an AC / DC correlation equation and an AC / DC power correlation equation in the AC / DC converter based on the power conservation principle of the AC / DC converter.

[0137] The second step is to construct a power control equation of the AC / DC converter under active power control mode and a power control equation of the AC / DC converter under reactive power control mode.

[0138] The third step is to construct a power flow calculation model of the AC / DC converter based on the AC / DC correlation equation, the AC / DC power correlation equation, the power control equation under the active power control mode, and the power control equation under the reactive power control mode.

[0139] In some embodiments of the present invention, it may be assumed that there is an AC / DC converter k between the AC node j and the DC node n. Then, the power flow calculation model 1 of the AC / DC converter k generates the following new equation:

[0140] The AC voltage and DC voltage correlation equation of the AC / DC converter k is as follows:

[0141]

[0142] At the same time, the relationship equation between AC power and DC power in AC / DC converter k is as follows:

[0143]

[0144] Among them, U DCn and U ACj They are: the voltage of DC node n and the voltage of AC node j after AC / DC converter k is added between AC node j and DC node n; M k is the modulation ratio of the AC / DC converter k; I DCn is the current at the DC node n; and are the voltage complex phasor and current complex phasor of AC node j in the rectangular coordinate system; α, β, γ refer to the loss coefficients of AC / DC converter k related to voltage, current and constant, respectively, and αU DCn 2 +βI DCn +γ is the total loss of AC / DC converter k.

[0145] In addition, for the control equation of the AC / DC converter k, one is selected from the following equation group (10) corresponding to the active type and one is selected from the following equation group (11) corresponding to the reactive type:

[0146]

[0147] Among them, P DCn0 , U DCn0 and k droopn These are the DC voltage droop control setting parameters, Q ACj0 , U ACj0 and k droopj Set the parameters for reactive power-AC voltage droop control, const is the reference value setting for each link; Im() refers to the imaginary part of the complex number.

[0148] Correspondingly, after executing step B, the above step A3 can be implemented through the following process:

[0149] The power flow calculation model of the DC power flow controller, the power flow calculation model of the DC transformer, and the power flow calculation model of the AC / DC converter are simultaneously added to the AC / DC power flow equation set to obtain the AC / DC power grid power flow calculation equation set.

[0150] In some embodiments of the present invention, the power flow calculation model of the DC power flow controller (including a single-branch DC power flow controller and a dual-branch DC power flow controller) of the flexible DC transmission system, the power flow calculation model of the DC transformer, and the power flow calculation model of the AC / DC converter mentioned above can be added to the AC / DC power flow equation set composed of the power flow calculation equations of each node mentioned above to obtain the AC / DC grid power flow calculation equation set of the flexible DC transmission system. In other words, the AC / DC grid power flow calculation equation set of the flexible DC transmission system is constructed by combining the above-mentioned formulas (1) to (11).

[0151] It should be noted that the above formulas (5) and (6) realize the establishment of a power flow calculation model for the DC power flow controller, that is, the use of voltage control variables to convert the influence of the DC power flow controller on the branch power flow into a correction of the node power, while the number of nodes will not increase, and the order and elements of the system node admittance matrix and Jacobian matrix will not change, thereby effectively solving the problem of increasing the computational complexity and amount of computation in conventional power flow calculation methods. At the same time, formula (7) realizes the establishment of a power flow calculation model for the DC transformer, which can also convert the influence of the DC transformer on the branch power flow into a correction of the node power. The functional effect is the same as that of the DC power flow controller, and takes into account the expression of the DC transformer ratio or power control in the equation. In addition, formulas (8) to (11) realize the establishment of a concise and clear power flow calculation model for AC / DC converters, which can be applied to the processing of various types of AC / DC nodes and various control methods.

[0152] In some embodiments of the present invention, for a flexible HVDC transmission system, constructing an AC / DC power flow calculation equation set can be achieved through the following steps:

[0153] Step 1: Establish a rectangular coordinate system power flow calculation equation that includes all AC and DC nodes in the flexible DC transmission system, that is, obtain the AC and DC power flow equation set mentioned above.

[0154] Step 2: Establish a power flow calculation model for the AC / DC converter in the flexible HVDC transmission system.

[0155] Step 3: Establish a power flow calculation model for the DC power flow controller (involving a single-branch DC power flow controller and a dual-branch DC power flow controller) in the flexible DC transmission system.

[0156] Step 4: Establish a power flow calculation model for the DC transformer in the flexible DC transmission system.

[0157] Step 5: Synchronously add the multiple power flow calculation models established in steps 2 to 4 to the AC / DC power flow equation set obtained in step 1, that is, construct a complete AC / DC power grid power flow calculation equation set containing multiple accumulator-type DC devices, that is, the AC / DC power grid power flow calculation equation set involved in the above embodiment.

[0158] Correspondingly, the Newton-Raphson method can be used to calculate the power flow using the AC / DC power flow equations obtained. Figure 3 As shown in FIG, an example of grid-type converter control is shown. It can be imagined that the precise configuration, that is, the further configuration, can also have the same Figure 3 Different configurations are shown. Figure 3 The CIGRE B4.72 standard DC grid model used in a real-world application is shown as an example. The DC grid has a voltage level of ±400 kV and includes 23 VSCs, 28 DC buses, DC power sources, and DC loads. It is connected to AC grids of 220 kV and 500 kV. The 220 kV AC grid is connected to clean energy and conventional power equipment, while the 500 kV AC grid is connected to two AC equivalent networks. The AC equivalent networks are represented by two equivalent machines, GE-1 and GE-2, which serve as balancing machines. The DC topology in this example is complex, encompassing various component and VSC connection methods. The AC and DC system connection methods are diverse, and multiple asynchronous AC systems exist. Figure 3 The system power flow calculation results obtained by the power flow calculation method for flexible DC transmission system provided by this solution are also presented. Figure 3 The bus voltage is in kV, indicated by blue numbers; the power is in MW, with the value and flow direction indicated by green numbers and arrows. The power flow results show that the power flowing through the line and converter, as well as the bus voltage, are within reasonable ranges.

[0159] Thus, the power flow calculation method for a flexible DC transmission system provided by an embodiment of the present invention is specifically a DC grid power flow calculation method that takes into account the various DC devices in the flexible DC transmission system and is applicable to power flow calculation and steady-state N-1 analysis for DC grids of any size. Specifically, this solution provides a grid-based control method for a flexible DC transmission system. Active control variables include DC voltage or active power, which are used to generate a threshold voltage phase reference value, and reactive control variables include reactive power or AC voltage amplitude, which are used to generate a threshold voltage amplitude reference value. To improve the tracking response speed of the active control variable, a phase feedforward compensation is generated based on the active control variable deviation. When the grid voltage phase exhibits a significant offset, active control variables and frequency and phase compensation values are generated based on the phase deviation, enabling wide-range grid phase tracking. This solution avoids the issues of increased node admittance matrix and Jacobian matrix order, element modification, and the resulting additional computational effort associated with the introduction of nodes by DC transformers and DC power flow controllers in traditional power flow calculation methods. Thus, this solution ensures both power flow calculation accuracy and computational speed and efficiency.

[0160] In other words, this patent proposes a method for calculating the DC power flow of a DC grid that takes into account a variety of DC devices. Among them, the power flow calculation model takes into account various control strategies of AC / DC converters, and the method based on voltage control variables adds a DC power flow controller and a DC transformer power flow calculation model. As a result, the impact of the equipment on the branch power flow can be converted into a correction to the node power, that is, it can avoid the increase in the number of nodes and can also be compatible with other control strategies of equipment that may appear in the future. This method can solve the power flow problem of AC / DC systems containing multiple DC devices, arbitrary DC topology forms, and arbitrary AC / DC connection methods; thereby ensuring the calculation accuracy of the power flow while ensuring the calculation speed and efficiency of the power flow calculation.

[0161] Example 2:

[0162] Based on the same inventive concept, the embodiment of the present invention further provides a power flow calculation system applicable to a flexible DC transmission system, see Figure 4 As shown, the system 400 includes:

[0163] An acquisition module 401 is configured to acquire a topological network state and operating parameters of a flexible HVDC system;

[0164] A calculation module 402 is configured to substitute the topological network state and the operating parameters into a set of AC / DC power flow calculation equations using the Newton-Raphson method to perform calculations to obtain the node power and line power of the flexible DC transmission system; the set of AC / DC power flow calculation equations includes a power flow calculation model of a DC power flow controller and a power flow calculation model of a DC transformer in the flexible DC transmission system.

[0165] Optionally, the system further includes:

[0166] an analysis module, configured to analyze the voltage-current relationship of each node in the flexible DC power transmission system to obtain a set of AC and DC power flow equations consisting of power flow calculation equations for each node;

[0167] A first establishing module is configured to establish a power flow calculation model of the DC power flow controller and a power flow calculation model of the DC transformer in the flexible DC power transmission system respectively by adopting a voltage control variable method;

[0168] A supplementing module is used to supplement the power flow calculation model of the DC power flow controller and the power flow calculation model of the DC transformer into the AC / DC power flow equation set to obtain the AC / DC power grid power flow calculation equation set.

[0169] Optionally, the first establishment module is specifically used to analyze the voltage of the DC node connected to the DC power flow controller and the superimposed DC voltage generated by the DC power flow controller by adopting the voltage control variable method to obtain the power flow calculation model of the DC power flow controller; and analyze the voltage of the DC node connected to the DC transformer, the ideal transformation ratio of the DC transformer and the equivalent series conductance of the DC transformer to obtain the power flow calculation model of the DC transformer.

[0170] Optionally, the DC power flow controller includes a single-branch DC power flow controller; the DC nodes connected to the DC power flow controller include node a and node b; and a power flow calculation model of the DC power flow controller satisfies the following formula:

[0171]

[0172] Among them, U DCa is the voltage of the node a; U DCb is the voltage of the node b; U p1 Y is the superimposed DC voltage generated by the single-branch DC power flow controller; ab is the conductance between the node a and the node b; ab is the control DC current target value of the single-branch DC power flow controller; P DCa is the power value of the node a; U DCi is the voltage of the i-th DC node connected to the node a; Y ai is the conductance between the node a and the ith DC node connected to it; P DCb is the power value of the node b; U DCj is the voltage of the jth DC node connected to the node b; Ybj is the conductance between the node b and the j-th DC node connected to it.

[0173] Optionally, the DC power flow controller includes: a dual-branch DC power flow controller; the dual branches are: a first branch including nodes c and d, and a second branch including nodes c and e; the power flow calculation model of the DC power flow controller satisfies the following formula:

[0174]

[0175] Among them, U DCc is the voltage of the node c; U DCd is the voltage of the node d; U p2 Y is the superimposed DC voltage generated by the dual-branch DC power flow controller on the first branch; cd is the conductance between the node c and the node d; I cd is the target value of the DC current controlled by the dual-branch DC power flow controller on the first branch; U DCe is the voltage of the node e; U p3 Y is the superimposed DC voltage generated by the dual-branch DC power flow controller on the second branch; ce is the conductance between the node c and the node e; I ce I is the target value of the DC current controlled by the dual-branch DC power flow controller on the second branch; set is the DC transfer control target value of the dual-branch DC power flow controller; P DCc is the power value of the node c; U DCm is the voltage of the mth DC node connected to the node c; Y cm is the conductance between the node c and the mth DC node connected to it; P DCd is the power value of the node d; U DCn is the voltage of the nth DC node connected to the node d; Y dn is the conductance between the node d and the nth DC node connected to it; P DCe is the power value of the node e; U DCl is the voltage of the lth DC node connected to the node e; Y el is the conductance between the node e and the lth DC node connected to it.

[0176] Optionally, the DC nodes connected to the DC transformer include: node f and node g; the power flow calculation model of the DC transformer satisfies the following formula:

[0177]

[0178] Among them, P DCf is the power value of the node f; U DCf is the voltage of the node f; U DCo is the voltage of the oth DC node connected to the node f; Y fo is the conductance between the node f and the oth DC node connected to it; U DCg is the voltage of the node g; T q is the ideal transformation ratio of the DC transformer; G q is the equivalent series conductance of the DC transformer; P DCg is the power value of the node g; U DCg is the voltage of the node g; U DCp is the voltage of the pth DC node connected to the node g; Y gp is the conductance between the node g and the pth DC node connected to it.

[0179] Optionally, the system 400 further includes: a second establishing module, configured to establish a power flow calculation model of the AC / DC converter based on a power conservation principle of the AC / DC converter in the flexible HVDC power transmission system;

[0180] Correspondingly, the supplementing module is further used to simultaneously supplement the power flow calculation model of the DC power flow controller, the power flow calculation model of the DC transformer, and the power flow calculation model of the AC / DC converter to the AC / DC power flow equation set to obtain the AC / DC power grid power flow calculation equation set.

[0181] Optionally, the second establishment module is specifically used to construct the AC / DC correlation equation and the AC / DC power correlation equation in the AC / DC converter based on the power conservation principle of the AC / DC converter; construct the power control equation of the AC / DC converter under the active power control mode, and the power control equation of the AC / DC converter under the reactive power control mode; based on the AC / DC correlation equation, the AC / DC power correlation equation, the power control equation under the active power control mode, and the power control equation under the reactive power control mode, construct a power flow calculation model of the AC / DC converter.

[0182] It should be noted that the description of the power flow calculation system 400 for a flexible DC transmission system is similar to the description of the embodiment of the power flow calculation method for a flexible DC transmission system described above, and has similar beneficial effects as the embodiment of the power flow calculation method for a flexible DC transmission system. For technical details not disclosed in the embodiment of the power flow calculation system for a flexible DC transmission system of the present invention, please refer to the description of the embodiment of the power flow calculation method for a flexible DC transmission system of the present invention for understanding.

[0183] Example 3

[0184] like Figure 5 As shown, the present invention also provides an electronic device 500, which may be a computer device, a single-chip microcomputer device, a smart mobile device, etc. In this embodiment, the electronic device 500 may include a processor 510, a memory 520, a transceiver component 530, etc. The memory 520, the processor 510, and the transceiver component 530 are connected via a bus 540. The memory 520 may be used to store an execution program, which may include instructions. The processor 510 is used to execute the instructions stored in the memory. The memory 520 may also be used to store data, which may be accessed and / or modified during the execution of the instructions.

[0185] The processor may be a central processing unit (CPU), or may be other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), field-programmable gate arrays (FPGA) or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. It is the computing core and control core of the terminal, and is suitable for implementing one or more instructions, specifically suitable for loading and executing one or more instructions in a storage medium to implement a corresponding method flow or corresponding function, so as to implement the steps of a power flow calculation method applicable to a flexible DC transmission system involved in the above embodiment.

[0186] Example 4

[0187] Based on the same inventive concept, the present invention also provides a readable storage medium, specifically an electronic device readable storage medium (Memory), which is a memory device in the electronic device for storing programs and data. It can be understood that the storage medium here can include both the built-in storage medium in the electronic device and the extended storage medium supported by the electronic device. The storage medium provides a storage space, which stores the operating system of the terminal. In addition, one or more instructions suitable for being loaded and executed by the processor are also stored in the storage space. These instructions can be one or more execution programs (including program codes). It should be noted that the storage medium here can be a high-speed RAM memory or a non-volatile memory (non-volatile memory), such as at least one disk memory. The processor loads and executes one or more instructions stored in the storage medium, which can implement the steps of a power flow calculation method applicable to a flexible direct current transmission system involved in the above embodiment.

[0188] It will be understood by those skilled in the art that embodiments of the present invention may be provided as methods, systems, or computer program products. Thus, the present invention may take the form of an entirely hardware embodiment, an entirely software embodiment, or an embodiment combining software and hardware. Furthermore, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to magnetic disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0189] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowcharts and / or block diagrams, as well as combinations of processes and / or blocks in the flowcharts and / or block diagrams, 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 produce 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 flowcharts and / or block diagrams. 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.

[0190] 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 an article of manufacture comprising an instruction device, which implements the process Figure 1 a process or multiple processes and / or boxes Figure 1The function specified in one or more boxes.

[0191] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operational steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing the instructions executed on the computer or other programmable device for implementing the process. Figure 1 a process or multiple processes and / or boxes Figure 1 A step that specifies a function in one or more boxes.

[0192] The above are merely embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention are included in the scope of the claims of the present invention to be approved.

Claims

1. A power flow calculation method applicable to a flexible direct current transmission system, characterized in that: The method comprises: Obtain the topological network status and operating parameters of the flexible DC transmission system; The topological network state and the operating parameters are substituted into a set of AC and DC power grid flow calculation equations using the Newton-Raphson method to perform calculations to obtain the node power and line power of the flexible DC transmission system. The set of AC and DC power grid flow calculation equations includes a flow calculation model of a DC power flow controller and a flow calculation model of a DC transformer in the flexible DC transmission system.

2. The method according to claim 1, characterized in that The process of constructing the AC / DC power grid flow calculation equation set includes: Analyzing the voltage-current relationship of each node in the flexible direct current transmission system to obtain an AC / DC power flow equation set consisting of power flow calculation equations for each node; By adopting a voltage control variable method, a power flow calculation model of the DC power flow controller and a power flow calculation model of the DC transformer in the flexible DC power transmission system are respectively established; The power flow calculation model of the DC power flow controller and the power flow calculation model of the DC transformer are added to the AC / DC power flow equation set to obtain the AC / DC power grid power flow calculation equation set.

3. The method according to claim 2, characterized in that The method of adopting voltage control variables to respectively establish a power flow calculation model of the DC power flow controller and a power flow calculation model of the DC transformer in the flexible DC power transmission system includes: By adopting the voltage control variable method, the voltage of the DC node connected to the DC power flow controller and the superimposed DC voltage generated by the DC power flow controller are analyzed to obtain a power flow calculation model of the DC power flow controller; The voltage of a DC node connected to the DC transformer, the ideal transformation ratio of the DC transformer, and the equivalent series conductance of the DC transformer are analyzed to obtain a power flow calculation model of the DC transformer.

4. The method according to claim 3, characterized in that The DC power flow controller includes: a single-branch DC power flow controller; the DC nodes connected to the DC power flow controller include: node a and node b; the power flow calculation model of the DC power flow controller satisfies the following formula: Among them, U DCa is the voltage of the node a; U DCb is the voltage of the node b; U p1 Y is the superimposed DC voltage generated by the single-branch DC power flow controller; ab is the conductance between the node a and the node b; ab is the control DC current target value of the single-branch DC power flow controller; P DCa is the power value of the node a; U DCi is the voltage of the i-th DC node connected to the node a; Y ai is the conductance between the node a and the ith DC node connected to it; P DCb is the power value of the node b; U DCj is the voltage of the jth DC node connected to the node b; Y bj is the conductance between the node b and the j-th DC node connected to it.

5. The method according to claim 3, characterized in that The DC power flow controller includes: a dual-branch DC power flow controller; the dual branches are: a first branch including nodes c and d, and a second branch including nodes c and e; the power flow calculation model of the DC power flow controller satisfies the following formula: Among them, U DCc is the voltage of the node c; U DCd is the voltage of the node d; U p2 Y is the superimposed DC voltage generated by the dual-branch DC power flow controller on the first branch; cd is the conductance between the node c and the node d; I cd is the target value of the DC current controlled by the dual-branch DC power flow controller on the first branch; U DCe is the voltage of the node e; U p3 Y is the superimposed DC voltage generated by the dual-branch DC power flow controller on the second branch; ce is the conductance between the node c and the node e; I ce I is the target value of the DC current controlled by the dual-branch DC power flow controller on the second branch; set is the DC transfer control target value of the dual-branch DC power flow controller; P DCc is the power value of the node c; U DCm is the voltage of the mth DC node connected to the node c; Y cm is the conductance between the node c and the mth DC node connected to it; P DCd is the power value of the node d; U DCn is the voltage of the nth DC node connected to the node d; Y dn is the conductance between the node d and the nth DC node connected to it; P DCe is the power value of the node e; U DCl is the voltage of the lth DC node connected to the node e; Y el is the conductance between the node e and the lth DC node connected to it.

6. The method according to any one of claims 3 to 5, characterized in that: The DC nodes connected to the DC transformer include: node f and node g; the power flow calculation model of the DC transformer satisfies the following formula: Among them, P DCf is the power value of the node f; U DCf is the voltage of the node f; U DCo is the voltage of the oth DC node connected to the node f; Y fo is the conductance between the node f and the oth DC node connected to it; U DCg is the voltage of the node g; T q is the ideal transformation ratio of the DC transformer; G q is the equivalent series conductance of the DC transformer; P DCg is the power value of the node g; U DCg is the voltage of the node g; U DCp is the voltage of the pth DC node connected to the node g; Y gp is the conductance between the node g and the pth DC node connected to it.

7. The method according to claim 2, characterized in that Before adding the power flow calculation model of the DC power flow controller and the power flow calculation model of the DC transformer to the AC / DC power flow equation set to obtain the AC / DC power grid power flow calculation equation set, the method further includes: Based on the power conservation principle of the AC / DC converter in the flexible DC power transmission system, a power flow calculation model of the AC / DC converter is established; The power flow calculation model of the DC power flow controller and the power flow calculation model of the DC transformer are added to the AC / DC power flow equation set to obtain the AC / DC power grid power flow calculation equation set, including: The power flow calculation model of the DC power flow controller, the power flow calculation model of the DC transformer, and the power flow calculation model of the AC / DC converter are simultaneously added to the AC / DC power flow equation set to obtain the AC / DC power grid power flow calculation equation set.

8. The method according to claim 7, characterized in that The power flow calculation model of the AC / DC converter is established based on the power conservation principle of the AC / DC converter in the flexible DC power transmission system, including: Based on the power conservation principle of the AC / DC converter, constructing an AC / DC correlation equation and an AC / DC power correlation equation in the AC / DC converter; Constructing a power control equation for the AC / DC converter in an active power control mode, and a power control equation for the AC / DC converter in a reactive power control mode; Based on the AC / DC correlation equation, the AC / DC power correlation equation, the power control equation under the active power control mode, and the power control equation under the reactive power control mode, a power flow calculation model of the AC / DC converter is constructed.

9. A power flow calculation system suitable for a flexible direct current transmission system, characterized in that: The system comprises: An acquisition module is used to obtain the topological network status and operating parameters of the flexible DC transmission system; A calculation module is configured to substitute the topological network state and the operating parameters into a set of AC and DC power grid flow calculation equations using a Newton-Raphson method to perform calculations, thereby obtaining a node power and a line power of the flexible DC transmission system; the set of AC and DC power grid flow calculation equations includes a flow calculation model of a DC power flow controller and a flow calculation model of a DC transformer in the flexible DC transmission system.

10. The system according to claim 9, characterized in that The system further comprises: an analysis module, configured to analyze the voltage-current relationship of each node in the flexible DC power transmission system to obtain a set of AC and DC power flow equations consisting of power flow calculation equations for each node; A first establishing module is configured to establish a power flow calculation model of the DC power flow controller and a power flow calculation model of the DC transformer in the flexible DC power transmission system respectively by adopting a voltage control variable method; A supplementing module is used to supplement the power flow calculation model of the DC power flow controller and the power flow calculation model of the DC transformer into the AC / DC power flow equation set to obtain the AC / DC power grid power flow calculation equation set.

11. The system according to claim 10, wherein: The first establishment module is specifically used to analyze the voltage of the DC node connected to the DC power flow controller and the superimposed DC voltage generated by the DC power flow controller by adopting the voltage control variable method to obtain the power flow calculation model of the DC power flow controller; and analyze the voltage of the DC node connected to the DC transformer, the ideal transformation ratio of the DC transformer, and the equivalent series conductance of the DC transformer to obtain the power flow calculation model of the DC transformer.

12. The system according to claim 11, characterized in that The DC power flow controller includes: a single-branch DC power flow controller; the DC nodes connected to the DC power flow controller include: node a and node b; the power flow calculation model of the DC power flow controller satisfies the following formula: Among them, U DCa is the voltage of the node a; U DCb is the voltage of the node b; U p1 Y is the superimposed DC voltage generated by the single-branch DC power flow controller; ab is the conductance between the node a and the node b; ab is the control DC current target value of the single-branch DC power flow controller; P DCa is the power value of the node a; U DCi is the voltage of the i-th DC node connected to the node a; Y ai is the conductance between the node a and the ith DC node connected to it; P DCb is the power value of the node b; U DCj is the voltage of the jth DC node connected to the node b; Y bj is the conductance between the node b and the j-th DC node connected to it.

13. The system according to claim 11, wherein: The DC power flow controller includes: a dual-branch DC power flow controller; the dual branches are: a first branch including nodes c and d, and a second branch including nodes c and e; the power flow calculation model of the DC power flow controller satisfies the following formula: Among them, U DCc is the voltage of the node c; U DCd is the voltage of the node d; U p2 Y is the superimposed DC voltage generated by the dual-branch DC power flow controller on the first branch; cd is the conductance between the node c and the node d; I cd is the target value of the DC current controlled by the dual-branch DC power flow controller on the first branch; U DCe is the voltage of the node e; U p3 Y is the superimposed DC voltage generated by the dual-branch DC power flow controller on the second branch; ce is the conductance between the node c and the node e; I ce I is the target value of the DC current controlled by the dual-branch DC power flow controller on the second branch; set is the DC transfer control target value of the dual-branch DC power flow controller; P DCc is the power value of the node c; U DCm is the voltage of the mth DC node connected to the node c; Y cm is the conductance between the node c and the mth DC node connected to it; P DCd is the power value of the node d; U DCn is the voltage of the nth DC node connected to the node d; Y dn is the conductance between the node d and the nth DC node connected to it; P DCe is the power value of the node e; U DCl is the voltage of the lth DC node connected to the node e; Y el is the conductance between the node e and the lth DC node connected to it.

14. The system according to any one of claims 11 to 13, characterized in that: The DC nodes connected to the DC transformer include: node f and node g; the power flow calculation model of the DC transformer satisfies the following formula: Among them, P DCf is the power value of the node f; U DCf is the voltage of the node f; U DCo is the voltage of the oth DC node connected to the node f; Y fo is the conductance between the node f and the oth DC node connected to it; U DCg is the voltage of the node g; T q is the ideal transformation ratio of the DC transformer; G q is the equivalent series conductance of the DC transformer; P DCg is the power value of the node g; U DCg is the voltage of the node g; U DCp is the voltage of the pth DC node connected to the node g; Y gp is the conductance between the node g and the pth DC node connected to it.

15. The system according to claim 10, wherein: The system further includes: a second establishing module for establishing a power flow calculation model of the AC / DC converter based on the power conservation principle of the AC / DC converter in the flexible DC power transmission system; Correspondingly, the supplementing module is further used to simultaneously supplement the power flow calculation model of the DC power flow controller, the power flow calculation model of the DC transformer, and the power flow calculation model of the AC / DC converter to the AC / DC power flow equation set to obtain the AC / DC power grid power flow calculation equation set.

16. The system according to claim 15, wherein: The second establishment module is specifically used to construct the AC / DC correlation equation and the AC / DC power correlation equation in the AC / DC converter based on the power conservation principle of the AC / DC converter; construct the power control equation of the AC / DC converter under the active power control mode, and the power control equation of the AC / DC converter under the reactive power control mode; based on the AC / DC correlation equation, the AC / DC power correlation equation, the power control equation under the active power control mode, and the power control equation under the reactive power control mode, construct a power flow calculation model of the AC / DC converter.

17. An electronic device, characterized in that: include: at least one processor and memory; The memory and the processor are connected via a bus; The memory is used to store one or more programs; When the one or more programs are executed by the at least one processor, the power flow calculation method applicable to a flexible direct current transmission system as claimed in any one of claims 1 to 8 is implemented.

18. A readable storage medium, characterized in that: An execution program is stored thereon, and when the execution program is executed, the power flow calculation method applicable to the flexible direct current transmission system as claimed in any one of claims 1 to 8 is implemented.

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