WO2018188393A1 - Linearized determination method and system for power flow of flexible direct-current power grid, and computer storage medium - Google Patents

Abstract

A linearized determination method and system for a power flow of a flexible direct-current power grid, and a computer storage medium. The method comprises: according to a control mode, decomposing a power flow of a flexible direct-current power grid into: a power flow distribution of a constant-voltage control node and a power flow distribution of a constant-power control node; calculating the power flow distribution of the constant-voltage control node; calculating the power flow distribution of the constant-power control node; and superimposing the power flow distribution of the constant-voltage control node and the power flow distribution of the constant-power control node to calculate a final linearized power flow result of the flexible direct-current power grid.

Description

Method and system for determining linear current of flexible DC power grid, computer storage medium

Cross-reference to related applications

The present application is based on a Chinese patent application filed on Jan. 13, 2017, the entire disclosure of which is hereby incorporated by reference.

Technical field

The present invention relates to a power flow calculation method for a flexible DC power grid in the power industry, and particularly relates to a method and system for determining a linear current of a flexible DC power grid, and a computer storage medium.

Background technique

Clean energy such as scenery will continue to develop rapidly. Various large-scale renewable energy sources are connected to the power grid. Traditional power equipment, power grid structure and operation technology are becoming more and more incapable of accepting ultra-large-scale renewable energy. It is necessary to develop new technologies, new equipment and new power grid structures to meet the future. A profound change in the energy landscape. Multi-terminal HVDC transmission system based on flexible DC and DC grid technology are one of the effective technical means to solve this problem. As an important part of the flexible grid dispatching operation, the flexible grid dispatching plan is an important link to ensure the safe and economic operation of the flexible grid. In the conventional AC grid dispatching plan business, the core technology relies on safety-constrained unit combination and safety-constrained economic dispatching. One of the key points of the technology is “grid safety constraint”, and the processing method is based on the characteristics of high-voltage power flow calculation. Linearize the AC power flow calculations to construct a linear optimization model that considers power flow constraints. In the flexible grid, the power flow linearization method in the AC grid is not suitable for the flexible grid because the power flow calculation differs greatly from the AC grid.

Summary of the invention

To solve the above technical problem, the embodiment of the present application provides a flexible DC power flow linearization determining method and system, and a computer storage medium.

The technical solution of the embodiment of the present application is a flexible power grid linear power flow calculation method considering a flexible DC power grid control mode, based on injection power description and node voltage control.

A method for calculating a power flow linearization of a flexible DC power grid provided by an embodiment of the present application includes:

The power flow of the flexible DC grid is decomposed into: the power flow distribution of the constant voltage control node and the power flow distribution of the fixed power control node;

Zeroing the injection power of the fixed power control node, setting the constant voltage control node to the control value, and calculating the power flow distribution of the constant voltage control node;

Calculating the power flow distribution of the fixed power control node based on the sensitivity of the injected power to the branch power of the flexible DC grid;

The power flow distribution of the fixed voltage control node and the power flow distribution of the fixed power control node are calculated to calculate the final flexible DC power grid linearization power flow result.

In an embodiment, before decomposing the power flow of the flexible DC power grid in a controlled manner, the method further includes:

For the node number of the flexible DC grid, the fixed power control node number is before the constant voltage control node number;

For the branch number of the flexible DC grid, a branch data set is formed, which is expressed as [branch number, head end node, end node, branch resistance];

A node admittance matrix is formed according to the node number and the branch data set.

In an embodiment, the calculating a power flow distribution of the constant voltage control node includes:

Setting all injection powers of the fixed power control node to zero;

The voltage of the constant voltage control node is set to a known control value, and the nonlinear equations are solved to obtain the power flow distribution P _{l,V of} all the branch fixed voltage control nodes.

In an embodiment, the calculating a power flow distribution of the power control node includes:

Calculating the sensitivity of the power of the fixed power control node to the branch power of the flexible DC grid;

The flexible DC grid branch power is expressed as a linear combination of injection power based on sensitivity.

In an embodiment, the power flow sensitivity of all the fixed power control nodes to any one of the flexible DC power grids is calculated according to the following formula:

The flexible DC grid branch power P _{l,P is} expressed as a linear combination of injection power, calculated according to the following formula:

Where: P _l,km is the injection power of the branch where the nodes k and m are located, P _i is the injection power of the node i, λ _i,l is the sensitivity of the node i to the branch l, and i ∈A represents all the constant power control Node, V _i is the voltage of node i, V _k is the voltage of node k, V _m is the voltage of node m, and G _ij is the conductance value between node i and node j, corresponding to the value of the admittance matrix of the node Negative, j∈I, denotes the node directly adjacent to node i, G _ii is the self-admittance of node i; P _{l, P} is the power flow distribution of the fixed power control node, i, j, k, m are constant power Control node.

In an embodiment, when the voltages of the nodes of the flexible DC grid are equal, the linearized power flow result of the flexible DC grid is calculated according to the following formula:

P _l =P _l,V +P _l,P

Where: P _{l, V} represents the power flow distribution of the fixed voltage control node, P _{l, P} is the branch power of the flexible DC grid, and P _l is the linearized power flow result of the flexible DC grid.

The flexible DC power flow linearization calculation system provided by the embodiment of the present application includes:

The decomposition module is configured to decompose the power flow of the flexible DC grid into: a power flow distribution of the constant voltage control node and a power flow distribution of the constant power control node;

a first calculation module configured to calculate a power flow distribution of the constant voltage control node;

a second calculation module configured to calculate a power flow distribution of the fixed power control node;

The third calculation module is configured to superimpose the power flow distribution of the constant voltage control node and the power flow distribution of the constant power control node to calculate the final flexible DC power grid linearization power flow result.

In an embodiment, the first computing module includes:

Setting a module configured to set all injection powers of the fixed power control node to 0;

The tidal current distribution calculation module of the branch is configured to set all the voltages of the constant voltage control nodes to known control values, solve the nonlinear equations, and calculate the tidal current distributions P _{l, V of} all the branches.

In an embodiment, the system further includes: a flexible DC grid description module configured to node the number of the flexible DC grid before the power flow of the flexible DC grid is decomposed according to the control mode, and the fixed power control node number is at the constant voltage control node. Before the numbering; the branch number of the flexible DC grid is formed into a branch data set, expressed as [tributary number, head end node, end node, branch resistance]; according to the node number and the branch data set, the node admittance is formed. matrix.

In an embodiment, the second computing module includes:

The sensitivity calculation module is configured to calculate a sensitivity of the power of the fixed power control node to the power of any one of the flexible DC power grids;

A linear combination calculation module configured to represent a flexible DC grid branch power as a linear combination of injection power based on sensitivity.

Compared with the prior art, the technical solutions provided by the embodiments of the present application have the following beneficial effects:

1. The traditional power flow calculation based on injection power is a nonlinear model. When it is necessary to adjust the injection power to adjust the power flow of the soft grid branch, it cannot be linearly expressed, and the analysis is difficult. The method for calculating the linearization of the power flow of the flexible grid in the embodiment of the present application is one of the key technologies for constructing the safety constraint economic dispatch model of the flexible DC grid.

2. Scheduling plan of the flexible straight grid When considering the safety constraints, the linearization of the straight flow is not realized, and the optimized scheduling can not be realized by the existing linear modeling method. The embodiment of the present application is a flexible power grid linear power flow calculation method based on injection power description and node voltage control, which is generally considered in the flexible DC power grid control mode.

3. Through the embodiment of the present application, the influence of the DC power fixed power control node on the branch power flow can be linearly described, which provides a feasible technical means for the fast power flow calculation and power flow control of the DC power grid.

DRAWINGS

1 is a flow chart of a method for determining a power flow linearization of a flexible DC power grid according to an embodiment of the present application;

2 is a schematic diagram of a 5-node flexible grid in the embodiment of the present application;

3 is a structural block diagram of a power flow linearization determining system for a flexible DC power grid according to an embodiment of the present application.

detailed description

The specific embodiments of the present application are further described in detail below with reference to the accompanying drawings.

The detailed description of the present application is fully illustrated by the following description and the accompanying drawings. Other embodiments may include structural, logical, electrical, process, and other changes. The examples represent only possible variations. Individual components and functions are optional unless explicitly required, and the order of operations may vary. Portions and features of some embodiments may be included or substituted for portions and features of other embodiments. The scope of the embodiments of the present application includes the entire scope of the claims, and all equivalents of the claims. These embodiments of the present application may be referred to herein by the term "invention" individually or collectively, for convenience only, and if more than one invention is disclosed, it is not intended to automatically limit the application. The scope is any single invention or inventive concept.

Embodiment 1

The embodiment of the present application provides a linear power flow calculation method for a flexible power grid based on injection power description and node voltage control considering a flexible DC power grid control mode. The flowchart is as shown in FIG. 1 and includes the following steps:

S1: Establish a flexible grid topology description according to constant voltage control and constant power control control mode:

The embodiment of the present application takes the 5-node flexible grid structure diagram shown in FIG. 2 as an example for subsequent description. The flexible grid of any number of nodes and any connection mode can be similarly obtained. The topology description of the flexible grid is no different from the conventional AC grid topology description. To ensure the integrity of the content description, it is still briefly described here.

S11, the node number is assigned to the flexible grid, and the fixed power control node number is ahead of the fixed voltage control node number. As shown in FIG. 2, the nodes 1, 2, and 3 are fixed power control, and the nodes 4 and 5 are fixed voltage control. .

S12, numbering the branches to form a branch data set, which is expressed as [branch number, head end node, end node, branch resistance]. For the branch 1 in Fig. 2, it is expressed as: [1, 1, 2, 2.35].

S13, according to the node number and the branch data set, form a node admittance matrix, the formation mode and physical meaning of the node admittance matrix are introduced in the power system analysis book, and will not be described herein. For the circuit shown in Fig. 2, the admittance matrix is as shown in equation (1).

S2: The change of the injection power of the fixed power control node can represent the change of the power flow of the flexible grid branch. But the node with constant voltage control will not work. In order to linearly express the branch power flow distribution of the flexible grid, the embodiment of the present application proposes to divide the branch power flow into two components: the power flow distribution caused by the constant voltage control node and the power flow distribution caused by the fixed power control node.

The relevant calculations for the calculation of the power flow of the flexible grid are as follows:

In order to clearly describe the subsequent content of the embodiment of the present application, the power flow calculation of the flexible power grid needs to be related and deduced, and the derivation process is as follows.

The power of the branch 1 between node i and node j in the flexible grid can be expressed as:

P _l,ij =(V _i -V _j )·G _i,j ·V _i (2)

In the formula, P _{l, ij} is the power flow of the branch l, V _i is the voltage of the node i, and G _ij is the conductance value between the node i and the node j, which is the value corresponding to the negative in the node admittance array.

The injected power of node i in a flexible grid can be expressed as the sum of the powers of all the branches connected to node i:

Where P _i is the injection power of node i, j ∈ I, which represents the node directly adjacent to node i, and performs expansion analysis of equation (3):

Where G _ii is the self-admittance of node i, which is the value corresponding to the node admittance array. The first term in the equation is only related to the voltage of node i itself, and the second term is related to the voltage of the adjacent node. Find the partial derivative of V _i for equation (4). Then find the partial derivative of V _i for any branch.

Equation (6) describes the partial derivative of any branch power versus node voltage, ie the sensitivity of the node voltage to the branch current. If the value on the right side of equation (6) can be found, it means that the power change of the branch can be described by the voltage change of the node. Dividing equation (6) by equation (5) can obtain the partial derivative of any branch power to node i injection power, that is, the sensitivity of node injection power to branch power.

If the value on the right side of equation (7) can be found, it indicates that the power variation of the branch can be described by the change in node injection power.

For the calculation of equations (6) and (7), it is closely related to the control mode of the node. First, any node type (6) and formula (7) only need to solve one. When the node is constant voltage control, the equation (6) is obtained; when the node is fixed power control, it is required to take the formula (7). ).

We first analyze the characteristics of equation (6). Since the equation contains both the voltage itself and the derivative of the voltage, it can be seen that the sensitivity of the node voltage to the branch current can be linearly expressed only in a very small voltage variation interval. Therefore, we do not calculate the value of equation (6) here. We believe that the node voltages of all constant voltage control are known values, and the influence of the voltage variation of the constant voltage control node on the branch current is not analyzed.

S3: Zero the injection power of the fixed power control node, set the constant voltage control node to the control value, and calculate the power flow distribution caused by the constant voltage control node:

According to the characteristics of the analytical formula (7), in the normal operation of the flexible grid, regardless of the control mode of the node, the voltage difference of each node is small. If the voltages of the nodes are equal, the equation (7) can be reduced to:

Then, the equation (8) is solved. At this time, in the equation (8), the partial derivatives of the nodes k, m and the nodes adjacent to i to V _i are all variables to be determined. When seeking

In addition to node i, we assume that the node injection power of other fixed power controls is constant. Therefore, the partial derivative of the other node injection power to V _i is equal to zero. That is, as shown in the following formula.

When analyzing equation (9), again assume that the voltages of the nodes are not much different, then equation (9) can be reduced to:

Equation (10) is actually a system of equations, except for node i itself and other nodes.

Are unknown. For an n-node system, there are n-1 unknowns. There are a node (without i-node) for false power control, and (n-1-a) for fixed voltage control. According to equation (10), a equation can be obtained, and since the remaining (n-1-a) nodes are controlled by constant voltage, the voltage is not affected by other nodes, and is directly available.

According to the comprehensive analysis, n-1 unknowns correspond to n-1 equations, and all can be obtained.

Value. At the same time, it is shown that according to equation (8), the ratio of all branch power changes to the node i injection power variation can be obtained, which also indicates that the power variation of the branch can be linearly expressed by the injection power variation of the fixed power control node. At this point, the sensitivity calculation of the node injection power to the branch current flow ends.

In step S3, first, all injection powers of the fixed power control node are set to 0;

The voltage of the constant voltage control node is set to a known control value, and the nonlinear equations are solved by the traditional numerical solution method to obtain the tidal current of all branches. This branch flow is expressed as P _l,V , which represents the distribution of the current flow caused by the constant voltage control node.

S4: Calculate the sensitivity of the power of the fixed power control node to the power of the soft grid branch, and express the soft straight branch power as a linear combination of injection power based on sensitivity:

In this step, firstly, according to the method (8) in the equation (2), the power flow sensitivity of all the fixed power control nodes to the branch 1 is obtained, and the branch power flow obtained at this time is expressed as P _{l, P} , which represents the distribution of currents caused by nodes controlled by constant power. Its calculation expression is:

Where P _i is the injection power of node i, and λ _i,l is the sensitivity of node i to branch l. i∈A represents all fixed power control nodes. This means that if a P _{i is} given arbitrarily, the corresponding branch power flow P _l can be directly obtained linearly.

S5: The tidal current distribution caused by the superposition of the constant voltage control node and the tidal current distribution caused by the fixed power control node form the final linearized power flow calculation result of the soft line:

Combining step S3 and step S4, the linear expression of the branch current at this time can be obtained as follows:

P _l =P _l,V +P _l,P (12)

Embodiment 2

The following is an example of the 5-node flexible grid diagram in Figure 2 to illustrate the entire calculation process. First, as shown in the figure, nodes 1, 2, and 3 are fixed power control nodes, nodes 4 and 5 are fixed voltage control nodes, node 4 has a control voltage of 319.5 kV, and node 5 has a control voltage of 320 kV. First, according to formula (10), the equations of nodes 1, 2, and 3 are as follows:

According to equation (13)

According to equation (14)

According to equation (15)

The sensitivity of the constant power node injection power to all branch powers can be obtained by taking the obtained partial derivative into equation (8).

Similarly, the sensitivity of other nodes to all branches can be obtained. The results are shown in Table 1.

Table 1 Sensitivity of 6 branches

The following is the effect calculated in accordance with step S3. The calculation results are shown in the table below.

The following is the effect calculated in accordance with step S3. The calculation results are shown in the table below.

Then, according to step S4 and step S5, the branch power flow distribution after the constant power control arbitrary injection power is obtained can be calculated.

Assume that node 1 injects power by 260 MW, node 2 injects power by 340 MW, and node 3 injects power of -450. The flows of the branches calculated according to the embodiment of the present application are shown in the following table.

Table 3: The voltage distribution of the branch after constant voltage control node and constant power control arbitrary injection power

	Branch road 1	Branch road 2	Branch 3	Branch 4	Branch road 5	Branch road 6
This application	-39.55	188.398	261.561	38.775	111.088	-74.301
Iterative method	-39.3475	189.134	262.605	38.0196	110.215	-74.3012
deviation	0.0051201	-0.003907	-0.003991	0.0194816	0.0078586	-2.69E-06

The comparison shows that the calculation accuracy of this algorithm is excellent.

Embodiment 3

Based on the same inventive concept, the embodiment of the present application further provides a flexible DC power flow linearization calculation system considering a DC control mode, and a structural block diagram thereof is shown in FIG. 3, including:

The decomposition module 301 is configured to decompose the power flow of the flexible DC grid into a power flow distribution of the constant voltage control node and a power flow distribution of the constant power control node according to the control manner;

The first calculating module 302 is configured to calculate a power flow distribution of the constant voltage control node;

The second calculating module 303 is configured to calculate a power flow distribution of the fixed power control node;

The third calculating module 304 is configured to calculate the final flexible DC grid linearized power flow result by superimposing the power flow distribution of the constant voltage control node and the power flow distribution of the constant power control node.

The system further includes: a flexible DC grid description module configured to parameterize the node number of the flexible DC grid before the power flow of the flexible DC grid is decomposed according to the control mode, and the constant power control node number is before the constant voltage control node number; The branch number of the network forms a branch data set, which is expressed as [branch number, head end node, end node, branch resistance]; and a node admittance matrix is formed according to the node number and the branch data set.

The first computing module includes:

Setting a module configured to set all injection powers of the fixed power control node to 0;

The tidal current distribution calculation module of the branch is configured to set all the voltages of the constant voltage control node to known control values, solve the nonlinear equations, and calculate the tidal current distribution of all the branches.

The second calculation module includes:

The sensitivity calculation module is configured to calculate a sensitivity of the power of the fixed power control node to the power of any one of the flexible DC power grids;

A linear combination calculation module configured to represent a flexible DC grid branch power as a linear combination of injection power based on sensitivity.

In practical applications, the functions implemented by each module in the flexible DC power flow linearization computing system can be implemented by a central processing unit (CPU) located in a flexible DC power flow linearization computing system. A processor (MPU, Micro Processor Unit), or a digital signal processor (DSP), or a Field Programmable Gate Array (FPGA).

The technical solution of the embodiment of the present application solves the traditional power flow calculation of the flexible power grid based on the injection power is a nonlinear model. When the power of the soft power grid branch needs to be adjusted by adjusting the injection power, it cannot be linearly expressed. Analysis is difficult. Scheduling plan for the flexible grid When considering the safety constraints, the linearization of the straight flow is not realized, and the problem of optimal scheduling can not be achieved by the existing linear modeling method.

Those skilled in the art will appreciate that embodiments of the present application can be provided as a method, system, or computer program product. Thus, the application can take the form of an entirely hardware embodiment, an entirely software embodiment, or a combination of software and hardware. Moreover, the application can take the form of a computer program product embodied on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) including computer usable program code.

The present application is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (system), and computer program products according to embodiments of the present application. It will be understood that each flow and/or block of the flowchart illustrations and/or FIG. These computer program instructions can be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing device to produce a machine for the execution of instructions for execution by a processor of a computer or other programmable data processing device. Means for implementing the functions specified in one or more of the flow or in a block or blocks of the flow chart.

The computer program instructions can also be stored in a computer readable memory that can direct a computer or other programmable data processing device to operate in a particular manner, such that the instructions stored in the computer readable memory produce an article of manufacture comprising the instruction device. The apparatus implements the functions specified in one or more blocks of a flow or a flow and/or block diagram of the flowchart.

These computer program instructions can also be loaded onto a computer or other programmable data processing device such that a series of operational steps are performed on a computer or other programmable device to produce computer-implemented processing for execution on a computer or other programmable device. The instructions provide steps for implementing the functions specified in one or more of the flow or in a block or blocks of a flow diagram.

Correspondingly, an embodiment of the present invention further provides a computer storage medium, wherein a computer program configured to perform a flexible DC power flow linearization calculation method according to an embodiment of the present invention is stored.

Finally, it should be noted that the above embodiments are only used to explain the technical solutions of the present application and are not limited thereto. Although the present application is described in detail with reference to the above embodiments, those skilled in the art can still implement the specific implementation of the present application. Modifications or equivalents are intended to be included within the scope of the appended claims.

Industrial applicability

The technical solution of the embodiment of the present application solves the traditional power flow calculation of the flexible power grid based on the injection power is a nonlinear model. When the power of the soft power grid branch needs to be adjusted by adjusting the injection power, it cannot be linearly expressed. Analysis is difficult. Scheduling plan for the flexible grid When considering the safety constraints, the linearization of the straight flow is not realized, and the problem of optimal scheduling can not be achieved by the existing linear modeling method.

Claims (11)

1. A flexible DC power flow linearization calculation method, the calculation method comprising the following steps:

   The power flow of the flexible DC grid is decomposed into: the power flow distribution of the constant voltage control node and the power flow distribution of the fixed power control node;

   Zeroing the injection power of the fixed power control node, setting the constant voltage control node to the control value, and calculating the power flow distribution of the constant voltage control node;

   Calculating the power flow distribution of the fixed power control node based on the sensitivity of the injected power to the branch power of the flexible DC grid;

   The power flow distribution of the fixed voltage control node and the power flow distribution of the fixed power control node are calculated to calculate the final flexible DC power grid linearization power flow result.
2. The method of calculating a power flow linearization of a flexible DC power grid according to claim 1, wherein the method further comprises: before decomposing the power flow of the flexible DC power grid in a control manner;

   For the node number of the flexible DC grid, the fixed power control node number is before the constant voltage control node number;

   For the branch number of the flexible DC grid, a branch data set is formed, which is expressed as [branch number, head end node, end node, branch resistance];

   A node admittance matrix is formed according to the node number and the branch data set.
3. The method of calculating a power flow linearization of a flexible DC power grid according to claim 1 or 2, wherein said calculating a power flow distribution of the constant voltage control node comprises:

   Setting all injection powers of the fixed power control node to zero;

   The voltage of the constant voltage control node is set to a known control value, and the nonlinear equations are solved to obtain the power flow distribution P _{l,V of} all the branch fixed voltage control nodes.
4. The power flow linearization calculation method for a flexible DC power grid according to claim 1 or 2, wherein the calculating the power flow distribution of the fixed power control node comprises:

   Calculating the sensitivity of the power of the fixed power control node to the branch power of the flexible DC grid;

   The flexible DC grid branch power is expressed as a linear combination of injection power based on sensitivity.
5. The power flow linearization calculation method for a flexible DC power grid according to claim 4, wherein the power flow sensitivity of all the fixed power control nodes to any one of the flexible DC power grids is calculated according to the following formula:

   

   The flexible DC grid branch power P _{l,P is} expressed as a linear combination of injection power, calculated according to the following formula:

   

   Where: P _l,km is the injection power of the branch where the nodes k and m are located, P _i is the injection power of the node i, λ _i,l is the sensitivity of the node i to the branch l, and i ∈A represents all the constant power control Node, V _i is the voltage of node i, V _k is the voltage of node k, V _m is the voltage of node m, and G _ij is the conductance value between node i and node j, corresponding to the value of the admittance matrix of the node Take negative, j∈I, denotes the node directly adjacent to node i, G _ii is the self-admittance of node i; P _{l, P} is the power flow distribution of the fixed power control node, i, j, k, m are all fixed Power control node.
6. The method for calculating a power flow linearization of a flexible DC power grid according to any one of claims 2 or 5, wherein when the voltages of the nodes of the flexible DC power grid are equal, the linearized power flow result of the flexible DC power grid is calculated according to the following formula:

   P _l =P _l,V +P _l,P

   Where: P _{l, V} represents the power flow distribution of the fixed voltage control node, P _{l, P} is the branch power of the flexible DC grid, and P _l is the linearized power flow result of the flexible DC grid.
7. A flexible DC power flow linearization calculation system, the system comprising:

   The decomposition module is configured to decompose the power flow of the flexible DC grid into: a tidal current distribution of the constant voltage control node and a power flow distribution of the constant power control node;

   a first calculation module configured to calculate a power flow distribution of the constant voltage control node;

   a second calculation module configured to calculate a power flow distribution of the fixed power control node;

   The third calculation module is configured to superimpose the power flow distribution of the constant voltage control node and the power flow distribution of the constant power control node to calculate the final flexible DC power grid linearization power flow result.
8. The flexible DC power grid power flow linearization calculation system of claim 7, wherein the first calculation module comprises:

   Setting a module configured to set all injection powers of the fixed power control node to 0;

   The tidal current distribution calculation module of the branch is configured to set all the voltages of the constant voltage control nodes to known control values, solve the nonlinear equations, and calculate the tidal current distributions P _{l, V of} all the branches.
9. The flexible DC grid power flow linearization calculation system according to claim 7, wherein the system further comprises: a flexible DC power grid description module configured to node the flexible DC power grid before decomposing the power flow of the flexible DC power grid according to a control manner No., the fixed power control node number is before the fixed voltage control node number; for the branch number of the flexible DC power grid, the branch data set is formed, which is expressed as [tributary number, head end node, end node, branch circuit resistance]; The node number and the branch data set form a node admittance matrix.
10. The flexible DC grid power flow linearization calculation system of claim 7, wherein the second calculation module comprises:

    The sensitivity calculation module is configured to calculate a sensitivity of the power of the fixed power control node to the power of any one of the flexible DC power grids;

    A linear combination calculation module configured to represent a flexible DC grid branch power as a linear combination of injection power based on sensitivity.
11. A computer storage medium having stored therein computer executable instructions configured to perform the flexible DC power flow current linearization calculation method of any of claims 1-6.

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