Transmission and distribution cooperative load flow calculation method and system

Abstract

The invention discloses a transmission and distribution cooperative load flow calculation method and system, and the method comprises the steps: a power distribution network internal circulation step: inputting a first boundary voltage of a boundary node into a dual-port network model of a power distribution network, and repeating forward-backward substitution operation to obtain boundary injection power; a power transmission network internal circulation step: inputting the boundary injection power into a power flow mapping model of the power transmission network, and obtaining and recording a first boundary voltage after the boundary node is updated; an iterative acceleration step: obtaining a second boundary voltage based on the recorded first boundary voltage in combination with a Stevanson acceleration algorithm; taking the second boundary voltage as the first boundary voltage; and an iteration stopping step: repeatedly executing the power distribution network internal circulation step, the power transmission network internal circulation step and the iteration acceleration step until the second boundary voltage meets the first convergence condition, and outputting load flow calculation results of the power transmission network and the power distribution network. According to the method, the convergence problem of the existing load flow calculation model can be effectively solved, and the convergence speed is improved.

Description

Technical Field

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

[0002] In power systems with low penetration of distributed energy, the traditional transmission and distribution network collaborative equivalent model is usually used to simplify the power flow calculation to improve the calculation efficiency. In this method, the distribution network is equivalent to the load when calculating the power flow of the transmission network, and the transmission network is equivalent to the power source when calculating the power flow of the distribution network. This equivalent processing method helps to reduce the scale of the calculation model. However, with the increasing number of distributed power sources connected to the distribution network, the response of distributed power sources to the state of the transmission network has become more complex, and the initiative of the distribution network has also been continuously enhanced, which has led to new challenges in the convergence and calculation efficiency of the traditional transmission and distribution collaborative equivalent model. Therefore, how to effectively establish a power flow calculation model for the transmission network-distribution network has become an urgent problem to be solved. Summary of the invention

[0003] The purpose of the embodiments of the present invention is to provide a method and system for calculating the coordinated power flow of transmission and distribution, which effectively solves the convergence problem of the existing power flow calculation model and improves the convergence speed by establishing power flow calculation models for the transmission network and the distribution network respectively, performing information exchange at the boundary nodes, and accelerating the iterative process in combination with the Stephenson acceleration algorithm.

[0004] The first embodiment of the present invention provides a transmission and distribution coordinated power flow calculation method, including:

[0005] Boundary voltage setting step: setting a first boundary voltage of a boundary node;

[0006] The circulation step in the distribution network is as follows: inputting the first boundary voltage into the two-port network model of the distribution network, and repeatedly performing forward and backward operations between the boundary node and the terminal node of the distribution network to obtain the boundary injection power and the voltage and current of each node in the distribution network; wherein the two-port network model is used to characterize the voltage relationship and current relationship between any node and another node;

[0007] The power transmission network internal circulation step: inputting the boundary injection power into the power flow mapping model of the power transmission network, performing power flow calculation of the power transmission network, and obtaining and recording the first boundary voltage after the boundary node is updated;

[0008] Iterative acceleration step: based on the first recorded boundary voltage, combined with Stephenson acceleration algorithm, obtain a second boundary voltage; and use the second boundary voltage as the first boundary voltage;

[0009] Iteration stop step: repeatedly executing the distribution network internal circulation step, the transmission network internal circulation step and the iterative acceleration step until the second boundary voltage meets the first convergence condition, and outputting the power flow calculation results of the transmission network and the distribution network.

[0010] Optionally, the two-port network model is as follows:

[0011]

[0012] Among them, V gabc is the three-phase voltage of the node to ground; I abc is the three-phase current passing through the node; n and m represent node n and node m in the distribution network respectively; A, B, C and D are all generalized matrices of the transmission line between the node n and the node m, which are used to characterize the transmission characteristics of the transmission line.

[0013] Optionally, the calculation formula between the voltage and current of each node in the distribution network is as follows:

[0014]

[0015] Among them, I n is the current at node n; S n is the complex power of node n; V n is the voltage at node n; * indicates taking the complex conjugate.

[0016] Optionally, the complex power of each node in the distribution network is determined by measurement information.

[0017] Optionally, the step of repeatedly performing a forward-backward operation between the boundary node and the end node of the distribution network to obtain boundary injection power and voltage and current of each node in the distribution network includes:

[0018] During the kth execution of the distribution network inner circulation step, the i-th forward-backward operation is performed between the boundary node and the terminal node of the distribution network through the two-port network model to obtain the corresponding third boundary voltage; wherein k≥1; i≥1;

[0019] When the third boundary voltage satisfies the second convergence condition, the forward push-back operation is stopped to obtain the boundary injection power and the voltage and current of each node in the distribution network.

[0020] Optionally, the power flow mapping model of the transmission network is as follows:

[0021] g T (S B )=U B ;

[0022] Among them, S B Inject power into the boundary; U B is the updated first boundary voltage of the boundary node; g T is a power flow function of the transmission network, and is used to characterize a power flow calculation process between a root node and a boundary node of the transmission network.

[0023] Optionally, inputting the boundary injection power into a power flow mapping model of a transmission network, performing power flow calculation of the transmission network, and obtaining and recording the updated first boundary voltage of the boundary node comprises:

[0024] During the kth execution of the transmission network internal circulation step, when the transmission network completes the power flow calculation and provides the single-phase voltage for the boundary node, the updated first boundary voltage of the boundary node is calculated and recorded according to the following formula:

[0025]

[0026] in, is the updated first boundary voltage of the boundary node, including voltage components of three phases a, b and c; and are the voltage amplitude and voltage phase corresponding to phase a in the first boundary voltage; and are the voltage amplitude and voltage phase corresponding to phase b in the first boundary voltage; and are the voltage amplitude and voltage phase corresponding to phase c in the first boundary voltage.

[0027] Optionally, the step of inputting the boundary injection power into a power flow mapping model of a transmission network, performing power flow calculation of the transmission network, and obtaining and recording the updated first boundary voltage of the boundary node further includes:

[0028] In the process of executing the transmission network internal circulation step for the kth time, when the boundary injection power is input into the power flow mapping model of the transmission network, and the power flow mapping model is a single-phase model, the input power of the power flow mapping model is calculated according to the following formula:

[0029]

[0030] in, The single-phase apparent power input into the power flow mapping model is used to characterize the single-phase apparent power injected into the transmission network by the boundary node; The single-phase active power input into the power flow mapping model; The single-phase reactive power input into the power flow mapping model; and The active powers corresponding to the three phases a, b and c in the boundary injection power transmitted by the distribution network; and It is the reactive power corresponding to the three phases a, b and c in the boundary injection power transmitted by the distribution network.

[0031] Optionally, the second boundary voltage is calculated by the following formula:

[0032]

[0033] in, is the second boundary voltage; is the first boundary voltage recorded for the dth time.

[0034] A second aspect of the present invention provides a transmission and distribution coordinated power flow calculation system, including:

[0035] A boundary voltage setting module, used for setting a first boundary voltage of a boundary node;

[0036] A distribution network internal circulation module, used for inputting the first boundary voltage into a two-port network model of the distribution network, and repeatedly performing forward and backward operations between the boundary node and the end node of the distribution network to obtain the boundary injection power and the voltage and current of each node in the distribution network; wherein the two-port network model is used to characterize the voltage relationship and current relationship between any node and another node;

[0037] A transmission network internal circulation module, used for inputting the boundary injection power into a power flow mapping model of the transmission network, performing power flow calculation of the transmission network, and obtaining and recording the first boundary voltage after the boundary node is updated;

[0038] An iterative acceleration module, configured to obtain a second boundary voltage based on the first boundary voltage recorded and in combination with a Stephenson algorithm; and use the second boundary voltage as the first boundary voltage;

[0039] The iteration stop module is used to repeatedly call the distribution network internal circulation module, the transmission network internal circulation module and the iteration acceleration module until the second boundary voltage meets the first convergence condition, and output the power flow calculation results of the transmission network and the distribution network.

[0040] An embodiment of the third aspect of the present invention provides a computer-readable storage medium, which includes a stored computer program; wherein, when the computer program is running, it controls the device where the computer-readable storage medium is located to execute the transmission and distribution coordinated power flow calculation method described in any embodiment of the first aspect above.

[0041] An embodiment of the fourth aspect of the present invention provides an electronic device, comprising a processor, a memory, and a computer program stored in the memory and configured to be executed by the processor, wherein the processor implements the transmission and distribution coordinated power flow calculation method described in any embodiment of the first aspect when executing the computer program.

[0042] Compared with the prior art, the embodiment of the present invention provides a transmission and distribution coordinated power flow calculation method and system, the method comprising: a boundary voltage setting step, setting a first boundary voltage of a boundary node; a distribution network internal circulation step, inputting the first boundary voltage into a two-port network model of the distribution network, and repeating forward and backward operations between the boundary node and the end node of the distribution network to obtain the boundary injection power and the voltage and current of each node in the distribution network; a transmission network internal circulation step, inputting the boundary injection power into a power flow mapping model of the transmission network, performing power flow calculation of the transmission network, obtaining and recording the first boundary voltage after the boundary node is updated; an iterative acceleration step, based on the recorded first boundary voltage, and in combination with the Stephenson acceleration algorithm, obtaining a second boundary voltage; and using the second boundary voltage as the first boundary voltage; an iterative stop step, repeatedly executing the distribution network internal circulation step, the transmission network internal circulation step and the iterative acceleration step, until the second boundary voltage meets the first convergence condition, outputting the power flow calculation results of the transmission network and the distribution network. The present invention establishes flow calculation models for the transmission network and the distribution network respectively, performs information exchange at the boundary nodes, and accelerates the iterative process in combination with the Stephenson acceleration algorithm, thereby effectively solving the convergence problem of the existing flow calculation model and improving the convergence speed. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 It is a flow chart of an embodiment of the transmission and distribution coordinated power flow calculation method provided by the present invention;

[0044] Figure 2 It is a schematic diagram of the divergence phenomenon that occurs when the general form of fixed point iteration is used to calculate the transmission and distribution coordinated power flow provided by the present invention;

[0045] Figure 3 It is a schematic diagram of an iterative curve for transmission and distribution coordinated power flow calculation using the Stephenson acceleration algorithm provided by the present invention;

[0046] Figure 4 It is a schematic diagram of the calculation results of the transmission and distribution coordinated power flow calculated by using the Stephenson acceleration algorithm provided by the present invention;

[0047] Figure 5 is a schematic diagram of an embodiment of a line model in a distribution network provided by the present invention;

[0048] Figure 6 It is a structural schematic diagram of an embodiment of the transmission and distribution coordinated power flow calculation system provided by the present invention;

[0049] Figure 7 It is a structural schematic diagram of an embodiment of an electronic device provided by the present invention. DETAILED DESCRIPTION

[0050] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this technical field without creative work are within the scope of protection of the present invention.

[0051] See also Figure 1 , is a flow chart of an embodiment of the transmission and distribution coordinated power flow calculation method provided by the present invention.

[0052] The first aspect of the present invention provides a method for calculating transmission and distribution coordinated power flow, including steps S1 to S5, which are specifically as follows:

[0053] Boundary voltage setting step S1: setting a first boundary voltage of a boundary node;

[0054] Distribution network internal circulation step S2: input the first boundary voltage into the two-port network model of the distribution network, and repeat the forward and backward operation between the boundary node and the end node of the distribution network to obtain the boundary injection power and the voltage and current of each node in the distribution network; wherein the two-port network model is used to characterize the voltage relationship and current relationship between any node and another node;

[0055] The power transmission network internal circulation step S3: inputting the boundary injection power into the power flow mapping model of the power transmission network, performing power flow calculation of the power transmission network, and obtaining and recording the updated first boundary voltage of the boundary node;

[0056] Iterative acceleration step S4: based on the first recorded boundary voltage, in combination with the Stephenson acceleration algorithm, a second boundary voltage is obtained; and the second boundary voltage is used as the first boundary voltage;

[0057] Iteration stop step S5: repeatedly executing the distribution network internal circulation step S2, the transmission network internal circulation step S3 and the iterative acceleration step S4 until the second boundary voltage meets the first convergence condition, and outputting the power flow calculation results of the transmission network and the distribution network.

[0058] It should be noted that the boundary node is the substation connecting the transmission network and the distribution network. The embodiment of the present invention abstracts the transmission and distribution coordinated power flow calculation problem into a fixed point iteration problem, establishes power flow calculation models for the transmission network and the distribution network respectively, and performs information exchange at the boundary nodes, as shown below:

[0059] (1) Distribution network power flow calculation formula:

[0060] g D (U B )=U Dabc ;

[0061] Among them, g D represents the power flow function of the distribution network, U B represents the first boundary voltage of the boundary node in the transmission and distribution system, U Dabc Represents the three-phase voltage of each node in the distribution network. This formula represents the three-phase power flow calculation process in the distribution network, which is expressed in the form of a single mapping operator, that is, the first boundary voltage at the given substation is taken as the voltage source of the distribution network, and the mapping g D Returns the three-phase voltage U of each node in the distribution network Dabc .

[0062] The distribution network power flow calculation formula corresponds to the forward push operation from the boundary node to the terminal node of the distribution network in the distribution network internal circulation step S2, and the forward push operation is realized through the dual-port network model of the distribution network.

[0063] (2) Boundary node power flow calculation formula:

[0064] g B (U B ,U Dabc )=S B ;

[0065] Among them, g B represents the power flow function of the substation, S B It represents the boundary injection power of the substation. This formula represents the power flow calculation process in the boundary node substation, which is expressed in the form of a single mapping operator. According to Kirchhoff's law, the boundary injection power is both the apparent power injected into the distribution network by the boundary node and the apparent power injected into the boundary area by the transmission network.

[0066] The boundary node power flow calculation formula corresponds to the back-substitution operation between the boundary node and the terminal node of the distribution network in the circulation step S2 within the distribution network, and the back-substitution operation is realized through the two-port network model of the distribution network.

[0067] (3) The power flow calculation formula of the transmission network, that is, the power flow mapping model of the transmission network, is as follows:

[0068] gT (S B )=U B ;

[0069] Among them, S B Inject power into the boundary; U B is the updated first boundary voltage of the boundary node; g T is the power flow function of the transmission network, used to characterize the power flow calculation process between the root node and the boundary node of the transmission network. The power flow calculation formula of the transmission network corresponds to the internal circulation step S3 of the transmission network.

[0070] The power flow calculation process of the transmission network can be performed through the forward and reverse power flows between the root node and the boundary node of the transmission network, and the forward and reverse traversal operations are realized through the active power balance equation and the reactive power balance equation between any two nodes, so as to obtain the power flow distribution from the transmission network to the boundary node. Of course, the specific power flow calculation process of the transmission network can also be implemented through other implementation methods, and the present invention is not limited to this.

[0071] It is worth noting that the subscript "D" in the formula or parameter in the present invention represents the distribution network, the subscript "B" represents the boundary node, the subscript "T" represents the transmission network, the subscript "abc" represents the three-phase power flow component including a, b, and c, and U in the present invention is B and S B If there is no superscript, it indicates the first boundary voltage and boundary injection power in any mapping process; after calculating the power flow of the transmission network, the updated first boundary voltage is the boundary voltage fed back by the transmission network to the distribution network, which is provided to the distribution network for internal circulation, and the first boundary voltage is the voltage source provided by the boundary node to the distribution network for internal circulation operation; the second boundary voltage = the first boundary voltage; the subsequent third boundary voltage is the intermediate state generated at the boundary node through the back substitution operation when executing the distribution network internal circulation step S2.

[0072] In addition, the embodiment of the present invention adopts the Steffensen acceleration algorithm, which can not only solve the convergence problem of the existing power flow calculation model, but also improve the convergence speed, as follows:

[0073] Combining the distribution network power flow calculation formula and the boundary node power flow calculation formula, we can get

[0074]

[0075] Among them, the definition To enhance the power flow mapping of the distribution network, the three-phase power flow of the distribution network is calculated as the first boundary voltage U B Boundary injection power S to the boundary node BA single mapping of . Mapping This corresponds to step S2 in the circulation within the distribution network.

[0076] Furthermore, the augmented distribution network power flow mapping and the transmission network power flow mapping model are combined into a composite mapping, namely, the fixed point iterative form of the transmission and distribution coordinated power flow calculation:

[0077]

[0078] The mapping Φ corresponds to the circulation step S2 within the distribution network and the circulation step S3 within the transmission network.

[0079] The fixed point iteration form of the transmission and distribution coordinated power flow calculation is exactly a fixed point problem, so it can be solved by fixed point iteration:

[0080] This formula corresponds to the iterative acceleration step S4 and the iterative stopping step S5.

[0081] Wherein, k is the number of iterations, i.e., the kth execution of the distribution network internal circulation step S2 and the transmission network internal circulation step S3; the first boundary voltage initially set is expressed as The first boundary voltage after executing k times of the distribution network internal circulation step S2 and the transmission network internal circulation step S3 is expressed as

[0082] In an optional embodiment, the second boundary voltage is calculated by the following formula:

[0083]

[0084] in, is the second boundary voltage; is the first boundary voltage recorded for the dth time.

[0085] It should be noted that according to the convergence theorem of fixed point iteration, the fixed point iteration form of transmission and distribution coordinated power flow calculation is The convergence behavior in the iterative process can be analyzed by the eigenvalue of the Jacobi matrix of the composite mapping, that is, for the iterative function Φ, if the spectral radius of its Jacobi matrix is ​​less than 1, then it is convergent, which can be expressed as:

[0086]

[0087] With the widespread access of renewable energy sources, the sensitivity of the injected power at the root node of the distribution network to the node voltage increases dramatically, which will cause the general form of fixed point iteration to fail to meet the convergence conditions.

[0088] The transmission and distribution coordination system verification example provided by the embodiment of the present invention is an IEEE standard example case 14 and a distribution network example case69_3p changed to three-phase. The distribution network example is connected to node 14 of the transmission network example case 14 through a transformer branch. At the same time, in the distribution network example, three-phase power supplies are added to nodes 6, 10, 32, and 59 respectively to simulate the scenario of high penetration rate of distributed power sources in the distribution network.

[0089] like Figure 2 As shown in the figure, when the verification example of the transmission and distribution coordinated system adopts the general iteration form, the first boundary voltage of the boundary node changes with the number of iterations. The first boundary voltage of the transmission and distribution coordinated system continues to diverge before 40 iterations, and oscillates in a larger area within 100 iterations, and ultimately fails to converge.

[0090] Based on this, the fixed point iteration problem in the embodiment of the present invention is solved by the Steffensen acceleration algorithm, which can solve the convergence problem, as follows:

[0091] The Steffensen acceleration algorithm is a nonlinear acceleration method in the fixed point iteration method, and its expression is:

[0092]

[0093] is equivalent to:

[0094]

[0095] in, is the second boundary voltage; is the first boundary voltage recorded for the dth time.

[0096] There exists a fixed point x * =Φ(x * ), and Φ'(x * )≠1, then the iteration of the above formula converges at least to the second order, and its convergence is proved as follows:

[0097]

[0098] It can be seen that the iterative form converges under the set conditions, and its convergence speed can be proved to be:

[0099]

[0100] Then, the derivative of the Steffensen acceleration at the fixed point can be calculated as follows:

[0101]

[0102] It can be proved that the fixed point acceleration method can approach the fixed point at a quadratic convergence rate, and in the transmission and distribution coordinated power flow calculation, it avoids the calculation divergence caused by the increase in the penetration rate of distributed energy in the distribution network. Figure 3 As shown in the figure, when the Steffensen acceleration algorithm is used in the verification example of the transmission and distribution coordinated system, the first boundary voltage of the boundary node changes with the number of iterations. The transmission and distribution coordinated power flow calculation reaches convergence after only 6 iterations. Figure 4 The three-phase voltage and phase angle of each node in the distribution network are displayed. For the convenience and intuitiveness of data display, the phase angle of phase B is +120° and the phase angle of phase C is -120°. It can be observed that the Steffensen acceleration algorithm ensures the accuracy of the transmission and distribution coordinated power flow calculation.

[0103] In an optional embodiment, the two-port network model is as follows:

[0104]

[0105] Among them, V gabc is the three-phase voltage of the node to ground; I abc is the three-phase current passing through the node; n and m represent node n and node m in the distribution network respectively; A, B, C and D are all generalized matrices of the transmission line between the node n and the node m, which are used to characterize the transmission characteristics of the transmission line.

[0106] It should be noted that the present invention provides the following specific embodiments to better illustrate the construction process of the two-port network model:

[0107] like Figure 5 The figure is a schematic diagram of an embodiment of a line model in a distribution network provided by the present invention. Figure 5 The line model in the paper adopts the accurate model of the three-phase line section of the three-phase overhead line and the underground line. In the modeling, a 3×3 matrix is ​​used to store the line impedance and admittance parameters, which are specifically expressed as:

[0108]

[0109] Among them, the r, x and c matrices are the matrices of the unit length resistance, unit length reactance and unit length admittance of the line respectively. The subscripts a, b, and c represent the three phases of the overhead line respectively. The self-impedance and self-admittance of each phase of the line and the mutual impedance and mutual admittance between the phases are stored here.

[0110] After defining the line model, different line types can be expressed by selecting different r, x and c matrices, and the corresponding node-to-node branch parameters can be obtained by setting the line length, that is, the three-phase impedance matrix Z abc And the three-phase admittance matrix Y abcBy using Kirchhoff's current law and voltage law between nodes, the three-phase line model is regarded as a two-port network, and the two-port network model can be obtained as follows:

[0111]

[0112] Among them, V gabc is the three-phase voltage of the node to ground, including the voltage components of phases a, b, and c; I abc is the three-phase current passing through the node, including the current components of phases a, b, and c; n and m represent nodes n and m in the distribution network respectively; A, B, C, and D are all generalized matrices of the transmission line between node n and node m, used to characterize the transmission characteristics of the transmission line. The two-port network model can deduce the voltage and current from one node (node ​​m) of the distribution line to another node (node ​​n).

[0113] The specific expression form of the generalized matrices A, B, C and D should be determined when the embodiment of the present invention is implemented, and the present invention does not limit this; based on this, the following expression is only an example reference:

[0114]

[0115] B=Z abc ;

[0116]

[0117] Where I is a 3×3 identity matrix.

[0118] It is worth noting that the two-port network model can realize the forward and backward operation between the boundary nodes and the end nodes of the distribution network.

[0119] In an optional embodiment, the calculation formula between the voltage and current of each node in the distribution network is as follows:

[0120]

[0121] Among them, I n is the current at node n; S n is the complex power of node n; V n is the voltage at node n; * indicates taking the complex conjugate.

[0122] Furthermore, the complex power of each node in the distribution network is determined by measurement information.

[0123] It should be noted that the loads in the distribution network are all set to constant complex power loads, and the forward-backward substitution method is used for calculation. The current of each node in the nonlinear network is calculated by the following formula:

[0124]

[0125] Among them, I n is the current at node n (usually any single-phase current); S n is the complex power of node n (usually the corresponding single-phase power); V n is the voltage of node n (usually the corresponding single-phase voltage); * indicates taking the complex conjugate. It should be noted that the three-phase voltage V gabc Equivalent to the three-phase voltage U at the distribution network node Dabc , V gabc The voltage corresponding to a certain phase in the n .

[0126] In the distribution network flow calculation process, the power generation equipment in the distribution network adopts a three-phase form, and its three-phase voltage to ground is V Gabc The output three-phase active power and three-phase reactive power are P Gabc , Q Gabc .

[0127] The load in the distribution network is modeled using three-phase, through the active power P dabc And power factor Defined as follows, the reactive power absorbed is:

[0128]

[0129] The power parameters involved in the complex power calculation of each node in the above distribution network (the three-phase voltage V Gabc , three-phase active power P Gabc With three-phase reactive power Q Gabc , and the active power P of the load node dabc and power factor ) are all imported parameters, which can be given by the measurement equipment or specified by the scheduling decision. They are known variables and do not need to be obtained through forward calculation.

[0130] Therefore, when pushing forward from the boundary node to node 1 in the distribution network, the boundary current injected into the distribution network by the boundary node and the voltage and current of node 1 can be obtained through the two-port network model and the calculation formula between the voltage and current of node 1.

[0131] In an optional embodiment, the step of repeatedly performing a forward-backward operation between the boundary node and the end node of the distribution network to obtain the boundary injection power and the voltage and current of each node in the distribution network includes:

[0132] During the kth execution of the distribution network inner circulation step, the i-th forward-backward operation is performed between the boundary node and the terminal node of the distribution network through the two-port network model to obtain the corresponding third boundary voltage; wherein k≥1; i≥1;

[0133] When the third boundary voltage satisfies the second convergence condition, the forward push-back operation is stopped to obtain the boundary injection power and the voltage and current of each node in the distribution network.

[0134] It should be noted that the distribution network and the transmission network in the embodiment of the present invention both exchange information at the boundary nodes after convergence in their respective iterative inner loops. Therefore, what is exchanged in the embodiment of the present invention is the first boundary voltage (i.e., the voltage source provided by the boundary node to the distribution network for the inner loop operation), rather than the third boundary voltage (i.e., the intermediate state generated at the boundary node through the back substitution operation when executing the distribution network inner loop step S2).

[0135] When executing the distribution network internal circulation step S2 for the first time, according to the two-port network model, the forward push-back operation is repeated for each line, that is, starting from the boundary node, the forward calculation is performed until a new voltage value is obtained at the end node, and then the new voltage at the end node is used to start the back-substitution calculation, so that a new power supply voltage calculation result can be obtained. The forward push-back calculation process is repeated continuously until the difference between the calculated voltage of the boundary node and the specified voltage transmitted to the boundary node by the initial transmission network is within the allowable error range, the forward push-back operation is stopped, and the injected power of the boundary node at this time is output to be transmitted to the power flow mapping model of the transmission network, and the transmission network internal circulation operation S3 is performed.

[0136] In an optional embodiment, the second convergence condition is specifically as follows:

[0137]

[0138] in, is the third boundary voltage corresponding to the jth forward-backward operation during the i-th execution of the distribution network internal circulation step ε 1 is the first preset convergence accuracy; V s The specified voltage that the transmission network initially delivers to the boundary nodes.

[0139] It is worth noting that in actual power systems, the three-phase imbalance of the distribution network is more obvious than that of the transmission network. Therefore, when performing high-precision transmission and distribution coordinated power flow calculations, the imbalance of the distribution network cannot be ignored. Based on this, the embodiment of the present invention can model the distribution network as a three-phase model, and can construct the transmission and distribution power system model in the following two ways:

[0140] (1) Full three-phase modeling: Both the transmission network and the distribution network are modeled in three phases. The advantage is that the calculation process is direct and the method is simple. However, due to the large amount of calculation, it may lead to a long calculation time and fail to fully utilize the inherent characteristics of the transmission network.

[0141] (2) Heterogeneous modeling: The transmission network is modeled as a single phase, while the distribution network is modeled as a three-phase model. Therefore, during the iterative calculation process, conversion is required at the boundary nodes to coordinate the single-phase modeling of the transmission network and the three-phase modeling of the distribution network.

[0142] In an optional embodiment, the step of inputting the boundary injection power into a power flow mapping model of a transmission network, performing power flow calculation of the transmission network, and obtaining and recording the updated first boundary voltage of the boundary node includes:

[0143] During the kth execution of the transmission network internal circulation step, when the transmission network completes the power flow calculation and provides the single-phase voltage for the boundary node, the updated first boundary voltage of the boundary node is calculated and recorded according to the following formula:

[0144]

[0145] in, is the updated first boundary voltage of the boundary node, including voltage components of three phases a, b and c; and are the voltage amplitude and voltage phase corresponding to phase a in the first boundary voltage; and are the voltage amplitude and voltage phase corresponding to phase b in the first boundary voltage; and are the voltage amplitude and voltage phase corresponding to phase c in the first boundary voltage.

[0146] It should be noted that in the heterogeneous modeling method, it is assumed that the three-phase voltages at the boundary nodes are symmetrical in each iteration step, that is, after the transmission network calculates the single-phase power flow, its unidirectional voltage is decomposed into symmetrical three-phase voltages. That is, any voltage component corresponding to the three phases a, b and c can be expressed as a single-phase voltage provided by the transmission network, such as and It is the single-phase first boundary voltage amplitude and the corresponding voltage phase transmitted by the transmission network to the boundary node after the transmission network completes the transmission network internal circulation step S3.

[0147] In an optional embodiment, the step of inputting the boundary injection power into a power flow mapping model of a transmission network, performing power flow calculation of the transmission network, and obtaining and recording the updated first boundary voltage of the boundary node further includes:

[0148] In the process of executing the transmission network internal circulation step for the kth time, when the boundary injection power is input into the power flow mapping model of the transmission network, and the power flow mapping model is a single-phase model, the input power of the power flow mapping model is calculated according to the following formula:

[0149]

[0150] in, The single-phase apparent power input into the power flow mapping model is used to characterize the single-phase apparent power injected into the transmission network by the boundary node; The single-phase active power input into the power flow mapping model; The single-phase reactive power input into the power flow mapping model; and The active powers corresponding to the three phases a, b and c in the boundary injection power transmitted by the distribution network; and It is the reactive power corresponding to the three phases a, b and c in the boundary injection power transmitted by the distribution network.

[0151] It should be noted that in the heterogeneous modeling method, the power flow calculation of the transmission network requires a single-phase The three-phase injected power transmitted from the distribution network to the boundary node can be obtained by calculating the three-phase power flow of the distribution network (after executing the inner circulation step S2 of the distribution network), that is, the three-phase injected active power of the distribution network includes and Three-phase injected reactive power includes and At the boundary nodes, the input power of the power flow mapping model can be obtained by summing the three-phase injected power of the distribution network.

[0152] See also Figure 6 , is a structural diagram of an embodiment of the transmission and distribution coordinated power flow calculation system provided by the present invention.

[0153] A second aspect of the present invention provides a transmission and distribution coordinated power flow calculation system, which is used to implement the transmission and distribution coordinated power flow calculation method described in the first aspect of the present invention. The system includes:

[0154] A boundary voltage setting module 11, used to set a first boundary voltage of a boundary node;

[0155] The distribution network internal circulation module 12 is used to input the first boundary voltage into the two-port network model of the distribution network, and repeat the forward and backward operation between the boundary node and the end node of the distribution network to obtain the boundary injection power and the voltage and current of each node in the distribution network; wherein the two-port network model is used to characterize the voltage relationship and current relationship between any node and another node;

[0156] The transmission network internal circulation module 13 is used to input the boundary injection power into the power flow mapping model of the transmission network, perform power flow calculation of the transmission network, and obtain and record the updated first boundary voltage of the boundary node;

[0157] An iterative acceleration module 14 is used to obtain a second boundary voltage based on the first boundary voltage recorded and in combination with a Stephenson algorithm; and use the second boundary voltage as the first boundary voltage;

[0158] The iteration stop module 15 is used to repeatedly call the distribution network internal circulation module, the transmission network internal circulation module and the iteration acceleration module until the second boundary voltage meets the first convergence condition, and output the power flow calculation results of the transmission network and the distribution network.

[0159] It should be noted that the transmission and distribution coordinated flow calculation system provided in the second embodiment of the present invention can implement all the processes of the transmission and distribution coordinated flow calculation method described in the first embodiment above. The functions of each module in the system and the technical effects achieved are respectively the same as the functions and technical effects achieved by the transmission and distribution coordinated flow calculation method described in the first embodiment above, and will not be repeated here.

[0160] An embodiment of the third aspect of the present invention provides a computer-readable storage medium, which includes a stored computer program; wherein, when the computer program is running, it controls the device where the computer-readable storage medium is located to execute the transmission and distribution coordinated power flow calculation method described in any embodiment of the first aspect above.

[0161] See also Figure 7 , is a structural diagram of an embodiment of an electronic device provided by the present invention.

[0162] An embodiment of the fourth aspect of the present invention provides an electronic device, comprising a processor, a memory, and a computer program stored in the memory and configured to be executed by the processor, wherein the processor implements the transmission and distribution coordinated power flow calculation method described in any embodiment of the first aspect when executing the computer program.

[0163] Preferably, the computer program can be divided into one or more modules / units (such as computer program 1, computer program 2, ...), and the one or more modules / units are stored in the memory 22 and executed by the processor 21 to complete the present invention. The one or more modules / units can be a series of computer program instruction segments that can complete specific functions, and the instruction segments are used to describe the execution process of the computer program in the electronic device.

[0164] The processor 21 can be a central processing unit (CPU), or other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), field-programmable gate arrays (FPGA) or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. The general-purpose processor can be a microprocessor, or the processor 21 can also be any conventional processor. The processor 21 is the control center of the electronic device, and various parts of the electronic device are connected using various interfaces and lines.

[0165] The memory 22 mainly includes a program storage area and a data storage area, wherein the program storage area can store an operating system, an application required for at least one function, etc., and the data storage area can store related data, etc. In addition, the memory 22 can be a high-speed random access memory, or a non-volatile memory, such as a plug-in hard disk, a smart memory card (Smart Media Card, SMC), a secure digital (Secure Digital, SD) card, and a flash card (Flash Card), etc., or the memory 22 can also be other volatile solid-state storage devices.

[0166] It should be noted that the above electronic device may include, but is not limited to, a processor and a memory. Those skilled in the art will understand that Figure 7 The structural diagram shown is only a structural example of the above-mentioned electronic device, and does not constitute a structural limitation of the above-mentioned electronic device. The above-mentioned electronic device may include more or less components than shown in the figure, or a combination of certain components, or different components.

[0167] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A transmission and distribution coordinated power flow calculation method, characterized in that: include: Boundary voltage setting step: setting a first boundary voltage of a boundary node; The circulation step in the distribution network is as follows: inputting the first boundary voltage into the two-port network model of the distribution network, and repeatedly performing forward and backward operations between the boundary node and the end node of the distribution network to obtain the boundary injection power and the voltage and current of each node in the distribution network; wherein the two-port network model is used to characterize the voltage relationship and current relationship between any node and another node; The power transmission network internal circulation step: inputting the boundary injection power into the power flow mapping model of the power transmission network, performing power flow calculation of the power transmission network, and obtaining and recording the first boundary voltage after the boundary node is updated; Iterative acceleration step: based on the first recorded boundary voltage, combined with Stephenson acceleration algorithm, obtain a second boundary voltage; and use the second boundary voltage as the first boundary voltage; Iteration stop step: repeatedly executing the distribution network internal circulation step, the transmission network internal circulation step and the iterative acceleration step until the second boundary voltage meets the first convergence condition, and outputting the power flow calculation results of the transmission network and the distribution network.

2. The transmission and distribution coordinated power flow calculation method according to claim 1, characterized in that: The two-port network model is as follows: Among them, V gabc is the three-phase voltage of the node to ground; I abc is the three-phase current passing through the node; n and m represent node n and node m in the distribution network respectively; A, B, C and D are all generalized matrices of the transmission line between the node n and the node m, which are used to characterize the transmission characteristics of the transmission line.

3. The transmission and distribution coordinated power flow calculation method according to claim 1, characterized in that: The calculation formula between the voltage and current of each node in the distribution network is as follows: Among them, I n is the current at node n; S n is the complex power of node n; V n is the voltage at node n; * indicates taking the complex conjugate.

4. The transmission and distribution coordinated power flow calculation method according to claim 1, characterized in that: The complex power of each node in the distribution network is determined by measurement information.

5. The transmission and distribution coordinated power flow calculation method according to claim 1, characterized in that: The step of repeatedly performing forward and backward operations between the boundary node and the terminal node of the distribution network to obtain boundary injection power and voltage and current of each node in the distribution network includes: During the kth execution of the distribution network inner circulation step, the i-th forward-backward operation is performed between the boundary node and the terminal node of the distribution network through the two-port network model to obtain the corresponding third boundary voltage; wherein k≥1; i≥1; When the third boundary voltage satisfies the second convergence condition, the forward push-back operation is stopped to obtain the boundary injection power and the voltage and current of each node in the distribution network.

6. The transmission and distribution coordinated power flow calculation method according to claim 1, characterized in that: The power flow mapping model of the transmission network is as follows: g T (S B )=U B ; Among them, S B Inject power into the boundary; U B is the updated first boundary voltage of the boundary node; g T is a power flow function of the transmission network, and is used to characterize a power flow calculation process between a root node and a boundary node of the transmission network.

7. The transmission and distribution coordinated power flow calculation method according to claim 1, characterized in that: The step of inputting the boundary injection power into a power flow mapping model of a transmission network, performing power flow calculation on the transmission network, and obtaining and recording the updated first boundary voltage of the boundary node includes: During the kth execution of the transmission network internal circulation step, when the transmission network completes the power flow calculation and provides the single-phase voltage for the boundary node, the updated first boundary voltage of the boundary node is calculated and recorded according to the following formula: in, is the updated first boundary voltage of the boundary node, including voltage components of three phases a, b and c; and are the voltage amplitude and voltage phase corresponding to phase a in the first boundary voltage; and are the voltage amplitude and voltage phase corresponding to phase b in the first boundary voltage; and are the voltage amplitude and voltage phase corresponding to phase c in the first boundary voltage.

8. The transmission and distribution coordinated power flow calculation method according to claim 7, characterized in that: The step of inputting the boundary injection power into a power flow mapping model of a transmission network, performing power flow calculation on the transmission network, and obtaining and recording the updated first boundary voltage of the boundary node further includes: In the process of executing the transmission network internal circulation step for the kth time, when the boundary injection power is input into the power flow mapping model of the transmission network, and the power flow mapping model is a single-phase model, the input power of the power flow mapping model is calculated according to the following formula: in, The single-phase apparent power input into the power flow mapping model is used to characterize the single-phase apparent power injected into the transmission network by the boundary node; The single-phase active power input into the power flow mapping model; The single-phase reactive power input into the power flow mapping model; and The active powers corresponding to the three phases a, b and c in the boundary injection power transmitted by the distribution network; and It is the reactive power corresponding to the three phases a, b and c in the boundary injection power transmitted by the distribution network.

9. The transmission and distribution coordinated power flow calculation method according to claim 1, characterized in that: The second boundary voltage is calculated by the following formula: in, is the second boundary voltage; is the first boundary voltage recorded for the dth time.

10. A transmission and distribution coordinated power flow calculation system, characterized in that: include: A boundary voltage setting module, used for setting a first boundary voltage of a boundary node; A distribution network internal circulation module, used for inputting the first boundary voltage into a two-port network model of the distribution network, and repeatedly performing forward and backward operations between the boundary node and the end node of the distribution network to obtain the boundary injection power and the voltage and current of each node in the distribution network; wherein the two-port network model is used to characterize the voltage relationship and current relationship between any node and another node; A transmission network internal circulation module, used for inputting the boundary injection power into a power flow mapping model of the transmission network, performing power flow calculation of the transmission network, and obtaining and recording the first boundary voltage after the boundary node is updated; An iterative acceleration module, configured to obtain a second boundary voltage based on the first boundary voltage recorded and in combination with a Stephenson algorithm; and use the second boundary voltage as the first boundary voltage; The iteration stop module is used to repeatedly call the distribution network internal circulation module, the transmission network internal circulation module and the iteration acceleration module until the second boundary voltage meets the first convergence condition, and output the power flow calculation results of the transmission network and the distribution network.

11. A computer-readable storage medium, characterized in that: The computer-readable storage medium includes a stored computer program; wherein, when the computer program is run, it controls the device where the computer-readable storage medium is located to execute the transmission and distribution coordinated power flow calculation method as described in any one of claims 1 to 9.

12. An electronic device, characterized in that: The method comprises a processor, a memory, and a computer program stored in the memory and configured to be executed by the processor, wherein the processor implements the transmission and distribution coordinated power flow calculation method as claimed in any one of claims 1 to 9 when executing the computer program.

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