Power grid coupling characteristic characterization method and device, storage medium and computer equipment

Abstract

The invention discloses a power grid coupling characteristic characterization method and device, a storage medium and computer equipment, and is applied to a receiving-end power grid. The method comprises the steps that a plurality of power receiving nodes in a receiving end power grid are acquired, energy of the power receiving nodes is direct current energy or new energy, and the new energy comprises wind power generation energy and photovoltaic power generation energy; selecting a power receiving node of which any energy is a direct-current energy source and a power receiving node of which any energy is a new energy source, and acquiring reactive voltage coupling characteristics among the selected power receiving nodes according to reactive voltage dynamic characteristics of the direct-current energy source and reactive voltage dynamic characteristics of the new energy source; and calculating a coupling degree value between the power receiving nodes based on the reactive voltage coupling characteristic between the selected power receiving nodes, and determining a coupling characteristic representation result between the selected power receiving nodes based on a comparison condition of the coupling degree value between the power receiving nodes and a preset coupling degree threshold, so that representation of the direct current and new energy cross-voltage grade coupling degree can be realized.

Description

Technical Field

[0001] The present application relates to the technical field of power systems, and in particular to a method and device for characterizing power grid coupling characteristics, a storage medium, and a computer device. Background Art

[0002] With the changes in the form of new power systems, some receiving power grids have the characteristics of multi-circuit DC feed-in, increasing proportion of new energy sources in the receiving power grids, and decreasing proportion of conventional power sources, showing strong power electronics characteristics. Compared with the voltage dynamic characteristics of conventional power sources, the external characteristics of power electronic equipment depend on the external characteristics of the converter and are closely related to the controller. If the proportion of DC feed-in increases, the conventional power sources in the receiving power grids are insufficient to start up and standby, and the reactive power support capacity of new energy sources is limited, the risk of transient voltage instability in the receiving power grids may increase. Summary of the invention

[0003] In view of this, the present application provides a method and device for characterizing power grid coupling characteristics, a storage medium, and a computer device, which are applied to a receiving-end power grid to obtain multiple power receiving nodes in the receiving-end power grid, wherein the energy of the power receiving nodes is DC energy or new energy, and the new energy includes wind power generation energy and photovoltaic power generation energy; select a power receiving node in which any energy is DC energy, and a power receiving node in which any energy is new energy, and obtain the reactive voltage coupling characteristics between the selected power receiving nodes according to the reactive voltage dynamic characteristics of the DC energy and the reactive voltage dynamic characteristics of the new energy; based on the reactive voltage coupling characteristics between the selected power receiving nodes, calculate the coupling degree value between the power receiving nodes, and based on the comparison between the coupling degree value between the power receiving nodes and the preset coupling degree threshold, determine the coupling characteristic characterization result between the selected power receiving nodes, which can realize the characterization of the coupling degree between DC and new energy across voltage levels.

[0004] According to one aspect of the present application, a method for characterizing power grid coupling characteristics is provided, which is applied to a receiving-end power grid; the method comprises:

[0005] Acquire multiple power receiving nodes in the receiving-end power grid, wherein the energy of the power receiving nodes is direct current energy or new energy, and the new energy includes wind power generation energy and photovoltaic power generation energy;

[0006] Select a power receiving node where any energy source is a DC energy source and a power receiving node where any energy source is a new energy source, and obtain reactive voltage coupling characteristics between the selected power receiving nodes according to the reactive voltage dynamic characteristics of the DC energy source and the reactive voltage dynamic characteristics of the new energy source;

[0007] Based on the reactive voltage coupling characteristics between the selected power receiving nodes, the coupling degree value between the power receiving nodes is calculated, and based on the comparison between the coupling degree value between the power receiving nodes and the preset coupling degree threshold, the coupling characteristic characterization result between the selected power receiving nodes is determined.

[0008] Optionally, the calculating the coupling degree value between the power receiving nodes based on the reactive voltage coupling characteristic between the selected power receiving nodes includes:

[0009] Obtain the voltage amplitude change of the selected power receiving node;

[0010] Based on the calculation formula of the coupling degree value between the power receiving nodes and the change of the voltage amplitude of each selected power receiving node, the coupling degree value between the power receiving nodes is calculated, wherein the calculation formula of the coupling degree value between the power receiving nodes is:

[0011]

[0012] D ij represents the coupling degree between the power receiving node i and the power receiving node j, α ij Indicates that the voltage amplitude change at the power receiving node j is ΔU j When , the voltage amplitude of the powered node i changes, α ji Indicates that the voltage amplitude change at the power receiving node i is ΔU i When , the voltage amplitude of the powered node j changes.

[0013] Optionally, obtaining the voltage amplitude change of the selected powered node includes:

[0014] Obtain the reactive power increment of each selected power receiving node;

[0015] Based on the voltage amplitude change calculation formula and the reactive power increment of each selected power receiving node, the voltage amplitude change of the selected power receiving node is calculated, wherein the voltage amplitude change calculation formula is:

[0016]

[0017] α ij Indicates that the voltage amplitude change at the power receiving node j is ΔU j When , the voltage amplitude of the powered node i changes, α ji Indicates that the voltage amplitude change at the power receiving node i is ΔU i When the voltage amplitude of the powered node j changes, μ i,j represents the voltage influence of power receiving node i on power receiving node j, and Respectively represent the reactive voltage coefficient of the receiving nodes i and j, ΔQ i and ΔQ j Represent the reactive power increment of the powered nodes i and j respectively.

[0018] Optionally, obtaining the reactive power increment of each selected power receiving node includes:

[0019] The reactive power increment of each selected power receiving node is calculated based on the reactive power increment calculation formula, wherein the reactive power increment calculation formula is:

[0020]

[0021] ΔQ i represents the reactive power increment of the receiving node i, and They represent the reactive voltage sensitivity of nodes i, j and the commutation bus node k of the DC converter station, ΔU i represents the voltage amplitude change of the power receiving node i, μ i,j represents the voltage influence of power receiving node i on power receiving node j, μ i,k It represents the influence of the receiving node i on the voltage of the converter bus node k of the converter station.

[0022] Optionally, before calculating the reactive power increment of each selected power receiving node based on the reactive power increment calculation formula, the method further includes:

[0023] Based on the first voltage influence calculation formula, the voltage influence between the power receiving nodes is calculated, and based on the second voltage influence calculation formula, the voltage influence between the power receiving node and the converter bus node of the converter station is calculated, wherein the first voltage influence calculation formula is:

[0024]

[0025] The second voltage influence degree calculation formula is:

[0026]

[0027] μ i,j represents the voltage influence of power receiving node i on power receiving node j, μ i,k It represents the influence of the receiving node i on the voltage of the converter bus node k of the converter station, ΔQ i represents the reactive power increment of the receiving node i, ΔQ i,j and ΔQ i,k They represent the reactive power increments from the power receiving node i to the power receiving node j and the power receiving node k respectively.

[0028] Optionally, the coupling degree value between the power receiving nodes represents the critical coupling degree between the DC energy and the new energy under the cross-voltage level, which is obtained by taking triggering the high voltage or low voltage ride-through of the new energy as the critical condition.

[0029] Optionally, the determining the coupling characteristic characterization result between the selected powered nodes based on the comparison between the coupling degree value between the powered nodes and a preset coupling degree threshold value includes:

[0030] When the coupling degree value between the power receiving nodes is greater than or equal to the preset coupling degree threshold, the coupling characteristic characterization result between the selected power receiving nodes is that there is a coupling relationship;

[0031] When the coupling degree value between the power receiving nodes is less than the preset coupling degree threshold, the coupling characteristic characterization result between the selected power receiving nodes is that there is no coupling relationship.

[0032] According to another aspect of the present application, a power grid coupling characteristic characterization device is provided, which is applied to a receiving-end power grid; the device comprises:

[0033] A power receiving node acquisition module, used to acquire multiple power receiving nodes in the receiving-end power grid, wherein the energy of the power receiving nodes is direct current energy or new energy, and the new energy includes wind power generation energy and photovoltaic power generation energy;

[0034] A coupling characteristic acquisition module is used to select a receiving node where any energy source is a DC energy source and a receiving node where any energy source is a new energy source, and acquire reactive voltage coupling characteristics between the selected receiving nodes according to the reactive voltage dynamic characteristics of the DC energy source and the reactive voltage dynamic characteristics of the new energy source;

[0035] The coupling characteristic characterization module is used to calculate the coupling degree value between the power receiving nodes based on the reactive voltage coupling characteristics between the selected power receiving nodes, and determine the coupling characteristic characterization result between the selected power receiving nodes based on the comparison between the coupling degree value between the power receiving nodes and the preset coupling degree threshold.

[0036] Optionally, the coupling characteristic characterization module is further used for:

[0037] Obtain the voltage amplitude change of the selected power receiving node;

[0038] Based on the calculation formula of the coupling degree value between the power receiving nodes and the change of the voltage amplitude of each selected power receiving node, the coupling degree value between the power receiving nodes is calculated, wherein the calculation formula of the coupling degree value between the power receiving nodes is:

[0039]

[0040] D ij represents the coupling degree between the power receiving node i and the power receiving node j, α ij Indicates that the voltage amplitude change at the power receiving node j is ΔU j When , the voltage amplitude of the powered node i changes, α ji Indicates that the voltage amplitude change at the power receiving node i is ΔU i When , the voltage amplitude of the powered node j changes.

[0041] Optionally, the coupling characteristic acquisition module is further used to:

[0042] Obtain the reactive power increment of each selected power receiving node;

[0043] Based on the voltage amplitude change calculation formula and the reactive power increment of each selected power receiving node, the voltage amplitude change of the selected power receiving node is calculated, wherein the voltage amplitude change calculation formula is:

[0044]

[0045] α ij Indicates that the voltage amplitude change at the power receiving node j is ΔU j When , the voltage amplitude of the powered node i changes, α ji Indicates that the voltage amplitude change at the power receiving node i is ΔU i When the voltage amplitude of the powered node j changes, μ i,j represents the voltage influence of power receiving node i on power receiving node j, and Respectively represent the reactive voltage coefficient of the receiving nodes i and j, ΔQ i and ΔQ j Represent the reactive power increment of the powered nodes i and j respectively.

[0046] Optionally, the coupling characteristic acquisition module is further used to:

[0047] The reactive power increment of each selected power receiving node is calculated based on the reactive power increment calculation formula, wherein the reactive power increment calculation formula is:

[0048]

[0049] ΔQ i represents the reactive power increment of the receiving node i, and They represent the reactive voltage sensitivity of nodes i, j and the commutation bus node k of the DC converter station, ΔU i represents the voltage amplitude change of the power receiving node i, μ i,j represents the voltage influence of power receiving node i on power receiving node j, μ i,k It represents the influence of the receiving node i on the voltage of the converter bus node k of the converter station.

[0050] Optionally, the coupling characteristic acquisition module is further used to:

[0051] Based on the first voltage influence calculation formula, the voltage influence between the power receiving nodes is calculated, and based on the second voltage influence calculation formula, the voltage influence between the power receiving node and the converter bus node of the converter station is calculated, wherein the first voltage influence calculation formula is:

[0052]

[0053] The second voltage influence degree calculation formula is:

[0054]

[0055] μ i,j represents the voltage influence of power receiving node i on power receiving node j, μ i,k It represents the influence of the receiving node i on the voltage of the converter bus node k of the converter station, ΔQ i represents the reactive power increment of the receiving node i, ΔQ i,j and ΔQ i,k They represent the reactive power increments from the power receiving node i to the power receiving node j and the power receiving node k respectively.

[0056] Optionally, the coupling degree value between the power receiving nodes represents the critical coupling degree between the DC energy and the new energy under the cross-voltage level, which is obtained by taking triggering the high voltage or low voltage ride-through of the new energy as the critical condition.

[0057] Optionally, the coupling characteristic characterization module is further used for:

[0058] When the coupling degree value between the power receiving nodes is greater than or equal to the preset coupling degree threshold, the coupling characteristic characterization result between the selected power receiving nodes is that there is a coupling relationship;

[0059] When the coupling degree value between the power receiving nodes is less than the preset coupling degree threshold, the coupling characteristic characterization result between the selected power receiving nodes is that there is no coupling relationship.

[0060] According to another aspect of the present application, a storage medium is provided, on which a computer program is stored, and when the program is executed by a processor, the above-mentioned method for characterizing power grid coupling characteristics is implemented.

[0061] According to another aspect of the present application, a computer device is provided, including a storage medium, a processor, and a computer program stored on the storage medium and executable on the processor, wherein the processor implements the above-mentioned method for characterizing grid coupling characteristics when executing the program.

[0062] By means of the above technical scheme, a method and device for characterizing the coupling characteristics of a power grid, a storage medium, and a computer device provided in the present application are applied to a receiving-end power grid to obtain multiple receiving nodes in the receiving-end power grid, wherein the energy of the receiving node is DC energy or new energy, and the new energy includes wind power generation energy and photovoltaic power generation energy; a receiving node whose energy is any DC energy and a receiving node whose energy is any new energy are selected, and the reactive voltage coupling characteristics between the selected receiving nodes are obtained according to the reactive voltage dynamic characteristics of the DC energy and the reactive voltage dynamic characteristics of the new energy; based on the reactive voltage coupling characteristics between the selected receiving nodes, the coupling degree value between the receiving nodes is calculated, and based on the comparison between the coupling degree value between the receiving nodes and the preset coupling degree threshold, the coupling characteristic characterization result between the selected receiving nodes is determined, which can realize the characterization of the coupling degree between DC and new energy across voltage levels.

[0063] The above description is only an overview of the technical solution of the present application. In order to more clearly understand the technical means of the present application, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0064] The drawings described herein are used to provide a further understanding of the present application and constitute a part of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0065] Figure 1 A schematic diagram of a flow chart of a method for characterizing power grid coupling characteristics provided in an embodiment of the present application is shown;

[0066] Figure 2 A grid node system diagram provided by an embodiment of the present application is shown;

[0067] Figure 3 A schematic diagram of a flow chart of another method for characterizing grid coupling characteristics provided in an embodiment of the present application is shown;

[0068] Figure 4 A schematic diagram of power balance of a DC system inverter station provided in an embodiment of the present application is shown;

[0069] Figure 5 A schematic diagram of a flow chart of a DC control system equation calculation method provided in an embodiment of the present application is shown;

[0070] Figure 6 A schematic diagram of a system under cross-voltage level coupling of high-voltage direct current and new energy provided in an embodiment of the present application is shown;

[0071] Figure 7A schematic diagram showing the relationship between a DC node and a new energy node and a voltage drop condition of the new energy node provided in an embodiment of the present application is shown;

[0072] Figure 8 A schematic diagram showing the relationship between a DC node and a new energy node and the voltage rise of the new energy node provided in an embodiment of the present application is shown;

[0073] Fig. 9 A schematic structural diagram of a power grid coupling characteristic characterization device provided in an embodiment of the present application is shown. DETAILED DESCRIPTION

[0074] The present application will be described in detail below with reference to the accompanying drawings and in combination with embodiments. It should be noted that the embodiments and features in the embodiments of the present application can be combined with each other without conflict.

[0075] In this embodiment, a method for characterizing power grid coupling characteristics is provided, such as Figure 1 As shown, applied to a receiving-end power grid, the method includes:

[0076] Step 101, obtaining a plurality of power receiving nodes in a receiving-end power grid, wherein the energy of the power receiving nodes is direct current energy or new energy, and the new energy includes wind power generation energy and photovoltaic power generation energy.

[0077] In the above embodiment of the present application, a method for characterizing the degree of reactive coupling between DC and renewable energy is proposed based on reactive voltage sensitivity when DC and renewable energy are coupled across voltage levels, that is, firstly, the reactive voltage dynamic characteristics of the DC transmission system under different grid fault conditions are analyzed, and then the reactive voltage dynamic characteristics of wind farms and photovoltaic power generation under different grid fault conditions are analyzed respectively, and finally, based on voltage reactive sensitivity, the reactive voltage coupling characteristics of DC and renewable energy are analyzed when they are connected across voltage levels. Specifically, Figure 2 As shown, multiple power receiving nodes in the receiving end power grid are obtained ( Figure 2 In the sequence numbers 1 to 38), the energy of the power receiving node is DC energy or new energy, and the new energy includes wind power generation energy and photovoltaic power generation energy.

[0078] Step 102, selecting a power receiving node where any energy source is a DC energy source and a power receiving node where any energy source is a new energy source, and obtaining reactive voltage coupling characteristics between the selected power receiving nodes according to the reactive voltage dynamic characteristics of the DC energy source and the reactive voltage dynamic characteristics of the new energy source.

[0079] Step 103, based on the reactive voltage coupling characteristics between the selected power receiving nodes, a coupling degree value between the power receiving nodes is calculated, and based on a comparison between the coupling degree value between the power receiving nodes and a preset coupling degree threshold, a coupling characteristic characterization result between the selected power receiving nodes is determined.

[0080] Next, a receiving node where any energy source is a DC energy source and a receiving node where any energy source is a new energy source are selected, and the reactive voltage coupling characteristics between the selected receiving nodes are obtained according to the reactive voltage dynamic characteristics of the DC energy source and the reactive voltage dynamic characteristics of the new energy source. Based on the reactive voltage coupling characteristics between the selected receiving nodes, the coupling degree value between the receiving nodes is calculated, and based on the comparison between the coupling degree value between the receiving nodes and the preset coupling degree threshold, the coupling characteristic characterization result between the selected receiving nodes is determined, so that the influence degree of the DC system and the new energy across the voltage level can be effectively evaluated.

[0081] By applying the technical solution of this embodiment, multiple power receiving nodes in the receiving-end power grid are obtained, and power receiving nodes in which any energy source is a DC energy source and any energy source is a new energy source are selected. According to the reactive voltage dynamic characteristics of the DC energy source and the reactive voltage dynamic characteristics of the new energy source, the reactive voltage coupling characteristics between the selected power receiving nodes are obtained. Based on the reactive voltage coupling characteristics between the selected power receiving nodes, the coupling degree value between the power receiving nodes is calculated, and based on the comparison between the coupling degree value between the power receiving nodes and the preset coupling degree threshold, the coupling characteristic characterization result between the selected power receiving nodes is determined. It is possible to characterize the coupling degree between DC and new energy across voltage levels based on the analysis of the impact of DC and new energy coupling on the transient voltage stability of the power grid system.

[0082] Further, as a refinement and extension of the specific implementation of the above embodiment, in order to fully illustrate the specific implementation process of this embodiment, another grid coupling characteristic characterization method is provided, which is applied to the receiving end grid, such as Figure 3 As shown, the method includes:

[0083] Step 201, obtaining a plurality of power receiving nodes in a receiving-end power grid, wherein the energy of the power receiving nodes is direct current energy or new energy, and the new energy includes wind power generation energy and photovoltaic power generation energy.

[0084] Step 202, select a power receiving node where any energy source is a DC energy source and a power receiving node where any energy source is a new energy source, and obtain reactive voltage coupling characteristics between the selected power receiving nodes according to the reactive voltage dynamic characteristics of the DC energy source and the reactive voltage dynamic characteristics of the new energy source.

[0085] In the above embodiment of the present application, multiple power receiving nodes in the receiving-end power grid are obtained, and a power receiving node whose energy source is a DC energy source and a power receiving node whose energy source is a new energy source are selected, and the reactive voltage coupling characteristics between the selected power receiving nodes are obtained according to the reactive voltage dynamic characteristics of the DC energy source and the reactive voltage dynamic characteristics of the new energy source. Specifically:

[0086] First, the reactive voltage characteristics of the inverter side of the DC transmission system are derived, such as Figure 4 As shown, Figure 4 It is a schematic diagram of power balance of DC system inverter station. d is the DC voltage on the inverter side; I d is the DC current; P d is the DC active power; Q d The reactive power consumed by the converter (including the converter transformer), i.e., the converter reactive power; U ac is the commutation bus voltage; Q c is the reactive power of the filter, i.e., the compensation reactive power, B c is the filter susceptance; Q a Exchange reactive power with the system for DC.

[0087] The algebraic equation of reactive power exchanged between the DC receiving end and the system is:

[0088]

[0089] U dr -U d =R d I d ,

[0090] P d =2U d I d ,

[0091]

[0092] Q a =Q d -Q c ,

[0093] U d0 is the DC no-load voltage on the inverter side; N is the number of 6-pulse converters per pole; T is the transformation ratio of the converter transformer; γ is the arc extinction angle on the inverter side; X c is the commutation reactance; is the power factor angle; U dr is the DC voltage on the rectifier side; R d is the DC line resistance; α is the trigger angle on the rectifier side; μ is the commutation overlap angle.

[0094] Since a short circuit in the receiving-end AC system can easily lead to a DC commutation failure or even a DC lockout, the dynamic characteristics of the reactive voltage on the inverter side of the DC system are closely related to the commutation bus voltage and the external characteristics of its converter.

[0095] In particular, since the DC control system equations are very complex and there are many nonlinear links such as limiting, it is difficult to directly use theoretical analytical methods to calculate. Generally, numerical integration methods and power system simulation software are required to solve them. The algorithm flow is as follows: Figure 5 shown.

[0096] After the new energy is connected to the grid, the relationship between its grid connection point voltage and the grid voltage is:

[0097]

[0098] is the grid connection point voltage; is the grid cluster point voltage; is the voltage drop on the transmission line; ΔU is the transverse voltage drop; δU is the longitudinal voltage drop.

[0099] For high-voltage long-distance transmission lines, the voltage drop transverse component δU is very small and can be ignored, so the amplitude of the grid connection point voltage can be approximately expressed as:

[0100]

[0101] R g +jX g is the impedance of the long-distance transmission line; P PCC and Q PCC They are respectively the active and reactive power output by the new energy power station.

[0102] When the grid voltage U S Constant. Under the premise that the line parameters have been determined, the grid connection point voltage depends on the output power of the new energy power station.

[0103] When the reactive power margin of the new energy power station is sufficient, the voltage stability of the grid connection point can be maintained by adjusting its output reactive power. When the reactive power output of the new energy power station is constant, it can be simplified as:

[0104]

[0105] in,

[0106]

[0107] Grid voltage U S Affected by the output power of the new energy power station and the grid voltage U PCC In the case of sufficient reactive power margin of the new energy power station, by adjusting the reactive power Q output PCC Increase the grid connection point voltage U PCC , the grid voltage U S of adjustment.

[0108] Next, the dynamic characteristics of reactive voltage of wind farms during high / low voltage ride-through are analyzed. When the grid voltage drops, the dynamic reactive current increment injected by the wind turbine should respond to the voltage change at the grid connection point and should meet the following requirements:

[0109] ΔI W=K1×(0.9-U PCC )×I WN (0.2≤U PCC ≤0.9,1.5≤K1≤3),

[0110] ΔI w U is the dynamic reactive current increment injected into the wind farm, in ampere (A); K1 is the dynamic reactive current proportional coefficient of the wind farm, and the value range of K1 should be no less than 1.5 and no more than 3; U PCC is the per unit voltage of the wind farm grid connection point, in units of per unit (pu); I WN is the rated current of the wind farm, in ampere (A).

[0111] When the grid voltage increases, the dynamic reactive current increment absorbed by the wind turbine should respond to the grid voltage change and meet the following requirements:

[0112] ΔI W =K2×(U PCC -1.1)×I WN (1.1≤U PCC ≤1.3,K2>1.5),

[0113] ΔI w is the dynamic reactive current increment absorbed by the wind farm, in ampere (A); K2 is the dynamic reactive current proportional coefficient of the wind farm, and the value range of K2 should be greater than 1.5; U PCC I is the voltage per unit value at the wind farm grid connection point; WN is the rated current of the wind farm, in ampere (A).

[0114] To this end, when a system fault causes the wind turbine to enter low voltage ride-through, the low voltage ride-through characteristics of the wind turbine will make the wind farm a "reactive source", causing the voltage on the wind turbine side and the converter bus to increase; when the wind farm enters high voltage ride-through, the high voltage ride-through characteristics of the wind farm will make the wind farm a "reactive load", causing the voltage on the wind turbine side and the converter bus to decrease.

[0115] Similarly, photovoltaic power stations have dynamic characteristics of reactive voltage. The dynamic reactive current output by the inverter should track the voltage changes at the grid connection point in real time and meet the following requirements:

[0116]

[0117] I pv_Q is the effective value of the dynamic reactive current output by the inverter; K3 and K4 are the ratio of the dynamic reactive current output by the inverter to the voltage change, the value range of K3 is 1.5-2.5, and the value range of K4 is 0-1.5; U PCC I is the voltage per unit value of the photovoltaic grid-connected point; N is the rated output current value of the inverter AC side.

[0118] The above embodiments list the reactive dynamic characteristics of the inverter side of direct current transmission, wind farms and photovoltaic power stations, and the coupling of reactive voltage characteristics when direct current and new energy are connected across voltage levels.

[0119] Step 203, calculating the reactive increment of each selected power receiving node based on the reactive increment calculation formula, wherein the reactive increment calculation formula is:

[0120]

[0121] ΔQ i represents the reactive power increment of the receiving node i, and They represent the reactive voltage sensitivity of nodes i, j and the commutation bus node k of the DC converter station, ΔU i represents the voltage amplitude change of the power receiving node i, μ i,j represents the voltage influence of power receiving node i on power receiving node j, μ i,k It represents the influence of the receiving node i on the voltage of the converter bus node k of the converter station.

[0122] Step 204, based on the first voltage influence calculation formula, the voltage influence between the power receiving nodes is calculated, and based on the second voltage influence calculation formula, the voltage influence between the power receiving node and the converter bus node of the converter station is calculated, wherein the first voltage influence calculation formula is:

[0123]

[0124] The second voltage influence degree calculation formula is:

[0125]

[0126] μ i,j represents the voltage influence of power receiving node i on power receiving node j, μ i,k It represents the influence of the receiving node i on the voltage of the converter bus node k of the converter station, ΔQ i represents the reactive power increment of the receiving node i, ΔQ i,j and ΔQ i,k They represent the reactive power increments from the power receiving node i to the power receiving node j and the power receiving node k respectively.

[0127] Next, the reactive power increment of each selected power receiving node is calculated based on the reactive power increment calculation formula.

[0128] Specifically, according to the power flow calculation equation, the relationship between the state variables P, Q, δ and U in the power grid system is:

[0129]

[0130] ΔP is the node active power increment; ΔQ is the node reactive power increment; Δδ is the node voltage angle increment; ΔU is the node voltage amplitude increment.

[0131] Only the influence of changing the reactive power of a node on the voltage amplitude of other nodes is considered, while the influence of the active power of the node is ignored, that is, the injection amount of active power is set to 0, and the sub-matrix of the Jacobian matrix in the correction equation is calculated.

[0132] From this we can get:

[0133]

[0134] Matrix S Q That is the reactive voltage sensitivity matrix.

[0135] Next, based on the first voltage influence calculation formula, the voltage influence between the power receiving nodes is calculated, and based on the second voltage influence calculation formula, the voltage influence between the power receiving node and the converter bus node of the converter station is calculated. Figure 6 As shown, Figure 6 This is a schematic diagram of the system with high voltage direct current and new energy coupled across voltage levels. Figure 6 Node i represents the bus node of interest, node k represents the commutation bus node of the DC converter station, and node j represents the grid connection point of the new energy source. Therefore:

[0136]

[0137] ΔQ i is the reactive power change of node i; are the reactive power-voltage sensitivity of node i, node j and node k respectively; ΔU i , ΔU j , ΔU k are the voltage changes at node i, node j, and node k respectively.

[0138] If reactive power compensation is implemented at the control station on the node i of interest, the initial voltage of the node is U i , when the control station adds reactive power ΔQ i When , let the reactive power flowing from node i to node j be ΔQ i,j , the reactive power flowing to node k is ΔQ i,k , the reactive power increment of node i itself is ΔQ i,i , reactive power-voltage sensitivity of node i, node j and node k and It can be expressed as:

[0139]

[0140] ΔU i , ΔU j and ΔU k Represent the voltage changes at node i, node j and node k respectively. The influence μ is used to measure the reactive power support of node i to node j and node k. i,i Indicates the influence of node i on its own node voltage, μ i,j and μ i,k They represent the ability of node i to adjust the voltage of node j and node k respectively:

[0141]

[0142] If we know μ i,j , μ i,k and the reactive power increment ΔQ of node i i , then the reactive power increment ΔQ flowing to node j and node k i,j and ΔQ i,k Can be expressed as:

[0143]

[0144] Finally, the reactive power increment ΔQ of the concerned node i under cross-voltage level coupling can be obtained: i The relationship with the node voltage increment is:

[0145]

[0146] and represents the reactive power-voltage sensitivity of nodes i, j and k; μ i,j and μ i,k Indicates the influence of node i on node j and node k; and Respectively represent the reactive power-voltage coefficient of node i, node j and node k, where:

[0147]

[0148] Step 205, based on the voltage amplitude change calculation formula and the reactive power increment of each selected power receiving node, the voltage amplitude change of the selected power receiving node is calculated, wherein the voltage amplitude change calculation formula is:

[0149]

[0150] μ i,j represents the voltage influence of power receiving node i on power receiving node j, and Respectively represent the reactive voltage coefficient of the receiving nodes i and j, ΔQi and ΔQ j Represent the reactive power increment of the powered nodes i and j respectively.

[0151] Next, based on the voltage amplitude change calculation formula and the reactive power increment of each selected power receiving node, the voltage amplitude change of the selected power receiving node is calculated.

[0152] Specifically, the relationship between voltage and reactive power is described as follows:

[0153]

[0154] α ij Indicates that the voltage amplitude change at node j is ΔU j The voltage amplitude of node i changes when α ji Indicates that the voltage amplitude change at node i is ΔU i The voltage amplitude of node j changes when .

[0155] Step 206, based on the calculation formula of the coupling degree value between the power receiving nodes and the change of the voltage amplitude of each selected power receiving node, the coupling degree value between the power receiving nodes is calculated, wherein the calculation formula of the coupling degree value between the power receiving nodes is:

[0156]

[0157] D ij represents the coupling degree between the power receiving node i and the power receiving node j, α ij Indicates that the voltage amplitude change at the power receiving node j is ΔU j When , the voltage amplitude of the powered node i changes, α ji Indicates that the voltage amplitude change at the power receiving node i is ΔU i When , the voltage amplitude of the powered node j changes.

[0158] Next, based on the calculation formula of the coupling degree value between the power receiving nodes and the voltage amplitude change of each selected power receiving node, the coupling degree value between the power receiving nodes is calculated. Specifically, the mathematical distance is mapped to the vector space using logarithmic transformation, and the coupling relationship D between the DC and the new energy based on the voltage-reactive sensitivity is defined. ij :

[0159] D ij =D ji =lg(α ij ×α ji +1)×10 2 ,

[0160] α ij ×α ji Yes to ensure D ij The symmetry of αij ×α ji +1 for ensuring D ij The positive definiteness of α ij ×α ji The larger the coefficient, the stronger the coupling between the two nodes; ij ×α ji The lower it is, the weaker the coupling between the two nodes.

[0161] Step 207, when the coupling degree value between the powered nodes is greater than or equal to the preset coupling degree threshold, the coupling characteristic characterization result between the selected powered nodes is that they have a coupling relationship, wherein the coupling degree value between the powered nodes represents the critical coupling degree between the DC energy and the new energy under the cross-voltage level obtained with the triggering of the new energy high voltage or low voltage ride-through as the critical condition.

[0162] Step 208: When the coupling degree value between the powered nodes is less than a preset coupling degree threshold, the coupling characteristic characterization result between the selected powered nodes is that there is no coupling relationship.

[0163] Finally, when the coupling degree value between the powered nodes is greater than or equal to the preset coupling degree threshold, the coupling characteristic characterization result between the selected powered nodes is that they have a coupling relationship; when the coupling degree value between the powered nodes is less than the preset coupling degree threshold, the coupling characteristic characterization result between the selected powered nodes is that they do not have a coupling relationship.

[0164] In particular, the coupling degree value between the power receiving nodes represents the critical coupling degree between the DC energy and the new energy under the cross-voltage level, which is obtained by taking the triggering of high voltage or low voltage ride-through of the new energy as the critical condition.

[0165] In a specific embodiment, for example Figure 2 As shown in Figure 1, the modified New England 10-machine 39-node system feeds DC into the power receiving node 8 as the DC node i, and connects new energy to the grid at nodes 5, 6, 32, and 34 as new energy nodes j. The sensitivity and coupling relationship between the DC node i and the new energy node j are calculated, and the results are shown in Table 1.

[0166] Table 1

[0167]

[0168] When a three-phase short circuit fault occurs in the transmission line between the DC nearby power receiving node 7 and the power receiving node 8, the relationship between the DC node i and the new energy node j and the voltage drop of the new energy node are as follows: Figure 7 When a bipolar blocking fault occurs in DC, the relationship between DC node i and new energy node j and the voltage rise of the new energy node are as follows: Figure 8 As shown. Figure 7 and Figure 8It can be seen that the voltage drop / rise at the renewable energy grid connection point is closely related to the coupling relationship between the DC node i and the renewable energy node j.

[0169] The new energy grid connection point can use the voltage amplitude of 0.9 and 1.1 as the threshold to obtain the critical coupling degree D0.9 and D1.1 of DC and new energy under the cross-voltage level. When the coupling degree D>D0.9 between the DC node and the new energy node, it indicates that there is a coupling relationship between them, and the larger the value of D, the stronger the coupling; vice versa; similarly, when the coupling degree D>D1.1 between the DC node and the new energy node, the above conclusion also holds true.

[0170] By applying the technical solution of this embodiment, first, the reactive voltage characteristics of the inverter side of the DC transmission system and the new energy grid-connected system are derived respectively. On this basis, the dynamic characteristics of the reactive voltage of the system under the coupling of DC and new energy across voltage levels are analyzed. Then, based on the concept of voltage reactive sensitivity, a method for characterizing the coupling characteristics of DC and new energy across voltage levels is proposed. Finally, whether the high / low voltage ride-through of new energy is triggered is used as the critical condition to obtain the critical coupling degree of DC and new energy across voltage levels. A simulation analysis is performed on the modified New England 10-machine 39-node system to verify the coupling degree between DC and new energy when a three-phase short circuit occurs in the near area of ​​the DC system, resulting in DC bipolar locking.

[0171] Further, as Figure 1 The specific implementation of the method, the embodiment of the present application provides a power grid coupling characteristic characterization device, which is applied to the receiving end power grid, such as Fig. 9 As shown, the device comprises:

[0172] The power receiving node acquisition module 301 is used to acquire multiple power receiving nodes in the receiving-end power grid, wherein the energy of the power receiving nodes is direct current energy or new energy, and the new energy includes wind power generation energy and photovoltaic power generation energy;

[0173] The coupling characteristic acquisition module 302 is used to select a power receiving node where any energy source is a DC energy source and a power receiving node where any energy source is a new energy source, and acquire the reactive voltage coupling characteristics between the selected power receiving nodes according to the reactive voltage dynamic characteristics of the DC energy source and the reactive voltage dynamic characteristics of the new energy source;

[0174] The coupling characteristic characterization module 303 is used to calculate the coupling degree value between the power receiving nodes based on the reactive voltage coupling characteristics between the selected power receiving nodes, and determine the coupling characteristic characterization result between the selected power receiving nodes based on the comparison between the coupling degree value between the power receiving nodes and the preset coupling degree threshold.

[0175] Optionally, the coupling characteristic characterization module 303 is further used for:

[0176] Obtain the voltage amplitude change of the selected power receiving node;

[0177] Based on the calculation formula of the coupling degree value between the power receiving nodes and the change of the voltage amplitude of each selected power receiving node, the coupling degree value between the power receiving nodes is calculated, wherein the calculation formula of the coupling degree value between the power receiving nodes is:

[0178]

[0179] D ij represents the coupling degree between the power receiving node i and the power receiving node j, α ij Indicates that the voltage amplitude change at the power receiving node j is ΔU j When , the voltage amplitude of the powered node i changes, α ji Indicates that the voltage amplitude change at the power receiving node i is ΔU i When , the voltage amplitude of the powered node j changes.

[0180] Optionally, the coupling characteristic acquisition module 302 is further used to:

[0181] Obtain the reactive power increment of each selected power receiving node;

[0182] Based on the voltage amplitude change calculation formula and the reactive power increment of each selected power receiving node, the voltage amplitude change of the selected power receiving node is calculated, wherein the voltage amplitude change calculation formula is:

[0183]

[0184] α ij Indicates that the voltage amplitude change at the power receiving node j is ΔU j When , the voltage amplitude of the powered node i changes, α ji Indicates that the voltage amplitude change at the power receiving node i is ΔU i When the voltage amplitude of the powered node j changes, μ i,j represents the voltage influence of power receiving node i on power receiving node j, and Respectively represent the reactive voltage coefficient of the receiving nodes i and j, ΔQ i and ΔQ j Represent the reactive power increment of the powered nodes i and j respectively.

[0185] Optionally, the coupling characteristic acquisition module 302 is further used to:

[0186] The reactive power increment of each selected power receiving node is calculated based on the reactive power increment calculation formula, wherein the reactive power increment calculation formula is:

[0187]

[0188] ΔQ i represents the reactive power increment of the receiving node i, and They represent the reactive voltage sensitivity of nodes i, j and the commutation bus node k of the DC converter station, ΔU i represents the voltage amplitude change of the power receiving node i, μ i,j represents the voltage influence of power receiving node i on power receiving node j, μ i,k It represents the influence of the receiving node i on the voltage of the converter bus node k of the converter station.

[0189] Optionally, the coupling characteristic acquisition module 302 is further used to:

[0190] Based on the first voltage influence calculation formula, the voltage influence between the power receiving nodes is calculated, and based on the second voltage influence calculation formula, the voltage influence between the power receiving node and the converter bus node of the converter station is calculated, wherein the first voltage influence calculation formula is:

[0191]

[0192] The second voltage influence degree calculation formula is:

[0193]

[0194] μ i,j represents the voltage influence of power receiving node i on power receiving node j, μ i,k It represents the influence of the receiving node i on the voltage of the converter bus node k of the converter station, ΔQ i represents the reactive power increment of the receiving node i, ΔQ i,j and ΔQ i,k They represent the reactive power increments from the power receiving node i to the power receiving node j and the power receiving node k respectively.

[0195] Optionally, the coupling degree value between the power receiving nodes represents the critical coupling degree between the DC energy and the new energy under the cross-voltage level, which is obtained by taking triggering the high voltage or low voltage ride-through of the new energy as the critical condition.

[0196] Optionally, the coupling characteristic characterization module 303 is further used for:

[0197] When the coupling degree value between the power receiving nodes is greater than or equal to the preset coupling degree threshold, the coupling characteristic characterization result between the selected power receiving nodes is that there is a coupling relationship;

[0198] When the coupling degree value between the power receiving nodes is less than the preset coupling degree threshold, the coupling characteristic characterization result between the selected power receiving nodes is that there is no coupling relationship.

[0199] It should be noted that for other corresponding descriptions of the functional units involved in the power grid coupling characteristic characterization device provided in the embodiment of the present application, reference can be made to Figure 1 and Figure 3 The corresponding description in the method will not be repeated here.

[0200] Based on the above Figure 1 and Figure 3 The method shown in the embodiment of the present application is accordingly provided with a storage medium on which a computer program is stored, and when the computer program is executed by a processor, the above-mentioned Figure 1 and Figure 3 The grid coupling characteristics characterization method shown.

[0201] Based on this understanding, the technical solution of the present application can be embodied in the form of a software product, which can be stored in a non-volatile storage medium (which can be a CD-ROM, a USB flash drive, a mobile hard disk, etc.), and includes a number of instructions for enabling a computer device (which can be a personal computer, a server, or a network device, etc.) to execute the methods described in each implementation scenario of the present application.

[0202] Based on the above Figure 1 and Figure 3 The method shown, and Fig. 9 In order to achieve the above-mentioned purpose, the embodiment of the present application further provides a computer device, which can be a personal computer, a server, a network device, etc. The computer device includes a storage medium and a processor; the storage medium is used to store a computer program; the processor is used to execute the computer program to achieve the above-mentioned Figure 1 and Figure 3 The grid coupling characteristics characterization method shown.

[0203] Optionally, the computer device may further include a user interface, a network interface, a camera, a radio frequency (RF) circuit, a sensor, an audio circuit, a WI-FI module, etc. The user interface may include a display, an input unit such as a keyboard, etc., and the optional user interface may also include a USB interface, a card reader interface, etc. The network interface may optionally include a standard wired interface, a wireless interface (such as a Bluetooth interface, a WI-FI interface), etc.

[0204] Those skilled in the art will appreciate that the computer device structure provided in this embodiment does not limit the computer device, and may include more or fewer components, or a combination of certain components, or different component arrangements.

[0205] The storage medium may also include an operating system and a network communication module. The operating system is a program that manages and saves the hardware and software resources of the computer device, and supports the operation of information processing programs and other software and / or programs. The network communication module is used to realize communication between the components inside the storage medium, and communication with other hardware and software in the physical device.

[0206] Through the description of the above implementation methods, those skilled in the art can clearly understand that the present application can be implemented by means of software plus a necessary general hardware platform, or can be implemented by hardware to obtain multiple power receiving nodes in the receiving-end power grid, wherein the energy of the power receiving node is DC energy or new energy, and the new energy includes wind power generation energy and photovoltaic power generation energy; select a power receiving node whose energy is any DC energy, and a power receiving node whose energy is any new energy, and obtain the reactive voltage coupling characteristics between the selected power receiving nodes according to the reactive voltage dynamic characteristics of the DC energy and the reactive voltage dynamic characteristics of the new energy; based on the reactive voltage coupling characteristics between the selected power receiving nodes, calculate the coupling degree value between the power receiving nodes, and based on the comparison between the coupling degree value between the power receiving nodes and the preset coupling degree threshold, determine the coupling characteristic characterization result between the selected power receiving nodes, so as to realize the characterization of the coupling degree between DC and new energy across voltage levels.

[0207] Those skilled in the art will appreciate that the accompanying drawings are only schematic diagrams of a preferred implementation scenario, and the modules or processes in the accompanying drawings are not necessarily necessary for implementing the present application. Those skilled in the art will appreciate that the modules in the devices in the implementation scenario can be distributed in the devices of the implementation scenario according to the description of the implementation scenario, or can be changed accordingly and located in one or more devices different from the present implementation scenario. The modules of the above-mentioned implementation scenario can be combined into one module, or can be further split into multiple submodules.

[0208] The above serial numbers of this application are only for description and do not represent the advantages and disadvantages of the implementation scenarios. The above disclosure is only a few specific implementation scenarios of this application, but this application is not limited to them, and any changes that can be thought of by technicians in this field should fall within the scope of protection of this application.

Claims

1. A method for characterizing power grid coupling characteristics, characterized in that: Applied to a receiving-end power grid; the method comprises: Acquire multiple power receiving nodes in the receiving-end power grid, wherein the energy of the power receiving nodes is direct current energy or new energy, and the new energy includes wind power generation energy and photovoltaic power generation energy; Select a power receiving node where any energy source is a DC energy source and a power receiving node where any energy source is a new energy source, and obtain reactive voltage coupling characteristics between the selected power receiving nodes according to the reactive voltage dynamic characteristics of the DC energy source and the reactive voltage dynamic characteristics of the new energy source; Based on the reactive voltage coupling characteristics between the selected power receiving nodes, the coupling degree value between the power receiving nodes is calculated, and based on the comparison between the coupling degree value between the power receiving nodes and the preset coupling degree threshold, the coupling characteristic characterization result between the selected power receiving nodes is determined.

2. The method according to claim 1, characterized in that The step of calculating the coupling degree value between the power receiving nodes based on the reactive voltage coupling characteristics between the selected power receiving nodes includes: Obtain the voltage amplitude change of the selected power receiving node; Based on the calculation formula of the coupling degree value between the power receiving nodes and the change of the voltage amplitude of each selected power receiving node, the coupling degree value between the power receiving nodes is calculated, wherein the calculation formula of the coupling degree value between the power receiving nodes is: D ij =D ji =lg(α ij ×α ji +1)×10 2 , D ij represents the coupling degree between the power receiving node i and the power receiving node j, α ij Indicates that the voltage amplitude change at the power receiving node j is ΔU j When , the voltage amplitude of the powered node i changes, α ji Indicates that the voltage amplitude change at the power receiving node i is ΔU i When , the voltage amplitude of the powered node j changes.

3. The method according to claim 2, characterized in that The obtaining of the voltage amplitude change of the selected powered node includes: Obtaining reactive power increment of each selected power receiving node; Based on the voltage amplitude change calculation formula and the reactive power increment of each selected power receiving node, the voltage amplitude change of the selected power receiving node is calculated, wherein the voltage amplitude change calculation formula is: α ij Indicates that the voltage amplitude change at the power receiving node j is ΔU j When , the voltage amplitude of the powered node i changes, α ji Indicates that the voltage amplitude change at the power receiving node i is ΔU i When the voltage amplitude of the power receiving node j changes, μ i,j represents the voltage influence of power receiving node i on power receiving node j, and Respectively represent the reactive voltage coefficient of the receiving nodes i and j, ΔQ i and ΔQ j Represent the reactive power increment of the powered nodes i and j respectively.

4. The method according to claim 3, characterized in that The step of obtaining the reactive power increment of each selected power receiving node includes: The reactive power increment of each selected power receiving node is calculated based on the reactive power increment calculation formula, wherein the reactive power increment calculation formula is: ΔQ i represents the reactive power increment of the receiving node i, and They represent the reactive voltage sensitivity of nodes i, j and the commutation bus node k of the DC converter station, ΔU i represents the voltage amplitude change of the power receiving node i, μ i,j represents the voltage influence of power receiving node i on power receiving node j, μ i,k It represents the influence of the receiving node i on the voltage of the converter bus node k of the converter station.

5. The method according to claim 4, characterized in that Before calculating the reactive power increment of each selected power receiving node based on the reactive power increment calculation formula, the method further includes: Based on the first voltage influence calculation formula, the voltage influence between the power receiving nodes is calculated, and based on the second voltage influence calculation formula, the voltage influence between the power receiving node and the converter bus node of the converter station is calculated, wherein the first voltage influence calculation formula is: The second voltage influence degree calculation formula is: μ i,j represents the voltage influence of power receiving node i on power receiving node j, μ i,k It represents the influence of the receiving node i on the voltage of the converter bus node k of the converter station, ΔQ i represents the reactive power increment of the receiving node i, ΔQ i,j and ΔQ i,k They represent the reactive power increments from the power receiving node i to the power receiving node j and the power receiving node k respectively.

6. The method according to claim 1, characterized in that The coupling degree value between the power receiving nodes represents the critical coupling degree between the DC energy and the new energy under the cross-voltage level, which is obtained by triggering the high voltage or low voltage ride-through of the new energy as the critical condition.

7. The method according to any one of claims 1 to 6, characterized in that The determining of the coupling characteristic characterization result between the selected powered nodes based on the comparison between the coupling degree value between the powered nodes and the preset coupling degree threshold value includes: When the coupling degree value between the power receiving nodes is greater than or equal to the preset coupling degree threshold, the coupling characteristic characterization result between the selected power receiving nodes is that there is a coupling relationship; When the coupling degree value between the power receiving nodes is less than the preset coupling degree threshold, the coupling characteristic characterization result between the selected power receiving nodes is that there is no coupling relationship.

8. A power grid coupling characteristic characterization device, characterized in that: Applicable to a receiving-end power grid; the device comprises: A power receiving node acquisition module, used to acquire multiple power receiving nodes in the receiving-end power grid, wherein the energy of the power receiving nodes is direct current energy or new energy, and the new energy includes wind power generation energy and photovoltaic power generation energy; A coupling characteristic acquisition module is used to select a receiving node where any energy source is a DC energy source and a receiving node where any energy source is a new energy source, and acquire reactive voltage coupling characteristics between the selected receiving nodes according to the reactive voltage dynamic characteristics of the DC energy source and the reactive voltage dynamic characteristics of the new energy source; The coupling characteristic characterization module is used to calculate the coupling degree value between the power receiving nodes based on the reactive voltage coupling characteristics between the selected power receiving nodes, and determine the coupling characteristic characterization result between the selected power receiving nodes based on the comparison between the coupling degree value between the power receiving nodes and the preset coupling degree threshold.

9. A storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the method for characterizing the coupling characteristics of a power grid as claimed in any one of claims 1 to 7 is implemented.

10. A computer device comprising a storage medium, a processor, and a computer program stored in the storage medium and executable on the processor, characterized in that: When the processor executes the computer program, the method for characterizing the coupling characteristics of a power grid as claimed in any one of claims 1 to 7 is implemented.

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