A method and system for initializing electromagnetic transient simulation of distribution network

Abstract

The present invention discloses a method and system for initializing electromagnetic transient simulation of a distribution network. A starting strategy based on three-phase asymmetric power flow calculation is used, and initialization is performed using the three-phase asymmetric power flow calculation result, so that the system quickly reaches a stable state and can run to a stable state in about 0.6s. Compared with the existing zero-state starting strategy, a system of the same size needs 6-8s, which greatly reduces the time consumption and improves the efficiency. Moreover, the method and system will not fail due to the complexity of the distribution network operation mode, and solves the technical problems that the existing zero-state starting strategy of the electromagnetic transient simulation of the distribution network adopts a long time consumption and is easy to fail due to the complexity of the distribution network.

Description

Technical Field

[0001] The present invention relates to the technical field of electromagnetic transient simulation, and in particular to a method and system for initializing electromagnetic transient simulation of a distribution network. Background Art

[0002] As an important part of digital simulation of power systems, electromagnetic transient simulation aims to finely model the target system and obtain detailed time domain waveforms of various transient responses. It was originally used to study overvoltage processes, subsynchronous resonance and other issues in power generation and transmission systems. With the development of distributed generation and microgrid technology, as well as the continuous development and application of intelligent power distribution and utilization technology, the distribution network has gradually changed from a traditional passive radial network to a multi-source complex network. Various distributed power sources, energy storage, microgrids, electric vehicles and users' diversified load demands have made the distribution system equipment more complex, the dynamic process more abundant and the control methods more diverse. It is necessary to use electromagnetic transient simulation technology to further study the operation mechanism and dynamic characteristics of the distribution network.

[0003] At present, the electromagnetic transient simulation of distribution network mainly adopts the zero-state starting strategy, that is, the power supply is started with a ramp voltage at the initial moment of the simulation, and the voltage, current and other state quantities of the transmission line, transformer and other equipment are set to 0 in the initial state, and then the node voltage method and step-by-step integration method are used to iteratively solve the system voltage, current and other state quantities. This strategy can help the entire system smoothly enter a stable state. However, the zero-state starting strategy is time-consuming and inefficient. With the continuous expansion of the scale of the distribution network, a large number of distributed power sources are connected to the grid. The access of distributed power sources makes the system operation more complicated, and the system flow direction changes from the traditional one-way flow to two-way flow. The system control method has also become more diverse. Under such conditions, the zero-state starting strategy may diverge and fail. Summary of the invention

[0004] The present invention provides a distribution network electromagnetic transient simulation initialization method and system, which are used to solve the technical problems that the existing distribution network electromagnetic transient simulation adopts a zero-state starting strategy, which is time-consuming and easily fails due to the complexity of the distribution network.

[0005] In view of this, a first aspect of the present invention provides a method for initializing electromagnetic transient simulation of a distribution network, comprising:

[0006] Build a simulation circuit for the distribution network system;

[0007] Calculating a node admittance matrix of the power distribution network system simulation circuit;

[0008] Calculating the three-phase asymmetric power flow of the power distribution network system simulation circuit;

[0009] The historical current of each component is calculated according to the node admittance matrix and the three-phase asymmetric power flow to obtain the initialization current of the node to be initialized.

[0010] Optionally, calculating a node admittance matrix of the power distribution network system simulation circuit includes:

[0011] Solve the branch admittance matrix of each component of the distribution network system simulation circuit;

[0012] The node admittance matrix is ​​solved according to the branch admittance matrix of each element.

[0013] Optionally, calculating the three-phase asymmetric power flow of the power distribution network system simulation circuit includes:

[0014] Initializing each phase voltage and phase angle of the power distribution network system simulation circuit;

[0015] Calculate the active deviation and reactive deviation injected into each phase of the node;

[0016] Calculate the voltage deviation and phase angle deviation of each phase of the node according to the active deviation and reactive deviation;

[0017] Update the voltage and phase angle of each phase according to the voltage deviation and phase angle deviation of each phase;

[0018] Output the updated phase voltage and phase angle when the iteration converges.

[0019] Optionally, the historical current of each component is calculated as:

[0020] I history (t-Δt)=m·V(t-Δt)+n·I(t-Δt)

[0021] Wherein, m is the voltage coefficient, n is the current coefficient, V(t-Δt) is the branch voltage for power flow calculation, and I(t-Δt) is the branch current for power flow calculation.

[0022] Optionally, when the effect of the capacitor is considered, the calculation formula for the historical current of the capacitor is:

[0023]

[0024] Where C is the equivalent capacitance of the Norton equivalent circuit,

[0025] When the effect of the capacitor is not considered, the calculation formula for the historical current of the transmission line is:

[0026] I history =[R*Δt+2L] -1 *ΔV(t-Δt)*Δt+[R*Δt+2L] -1*[2L-R*Δt]*[I RL (t-Δt)]

[0027] Where R is the equivalent resistance of the Norton equivalent circuit, L is the equivalent inductance of the Norton equivalent circuit, ΔV is the branch voltage for power flow calculation, and I RL is the current at both ends of the line.

[0028] A second aspect of the present invention provides a distribution network electromagnetic transient simulation initialization system, comprising:

[0029] Simulation circuit construction module, used to build distribution network system simulation circuit;

[0030] A node admittance calculation module, used to calculate the node admittance matrix of the power distribution network system simulation circuit;

[0031] A three-phase asymmetric power flow calculation module, used to calculate the three-phase asymmetric power flow of the distribution network system simulation circuit;

[0032] The historical current calculation module is used to calculate the historical current of each component according to the node admittance matrix and the three-phase asymmetric power flow to obtain the initialization current of the node to be initialized.

[0033] Optionally, the node admittance calculation module is specifically used for:

[0034] Solve the branch admittance matrix of each component of the distribution network system simulation circuit;

[0035] The node admittance matrix is ​​solved according to the branch admittance matrix of each element.

[0036] Optionally, the three-phase asymmetric power flow calculation module is specifically used for:

[0037] Initializing each phase voltage and phase angle of the power distribution network system simulation circuit;

[0038] Calculate the active deviation and reactive deviation injected into each phase of the node;

[0039] Calculate the voltage deviation and phase angle deviation of each phase of the node according to the active deviation and reactive deviation;

[0040] Update the voltage and phase angle of each phase according to the voltage deviation and phase angle deviation of each phase;

[0041] Output the updated phase voltage and phase angle when the iteration converges.

[0042] Optionally, the historical current of each component is calculated as:

[0043] I history (t-Δt)=m·V(t-Δt)+n·I(t-Δt)

[0044] Wherein, m is the voltage coefficient, n is the current coefficient, V(t-Δt) is the branch voltage for power flow calculation, and I(t-Δt) is the branch current for power flow calculation.

[0045] Optionally, when the effect of the capacitor is considered, the calculation formula for the historical current of the capacitor is:

[0046]

[0047] Where C is the equivalent capacitance of the Norton equivalent circuit,

[0048] When the effect of the capacitor is not considered, the calculation formula for the historical current of the transmission line is:

[0049] I history =[R*Δt+2L] -1 *ΔV(t-Δt)*Δt+[R*Δt+2L] -1 *[2L-R*Δt]*[I RL (t-Δt)]

[0050] Where R is the equivalent resistance of the Norton equivalent circuit, L is the equivalent inductance of the Norton equivalent circuit, ΔV is the branch voltage for power flow calculation, and I RL is the current at both ends of the line.

[0051] It can be seen from the above technical solutions that the embodiments of the present invention have the following advantages:

[0052] The present invention provides a method for initializing electromagnetic transient simulation of a distribution network. The method uses a starting strategy based on three-phase asymmetric power flow calculation and uses the three-phase asymmetric power flow calculation result for initialization, so that the system can quickly reach a stable state and can run to a stable state in about 0.6s. Compared with the existing zero-state starting strategy, a system of the same size needs 6-8s, which greatly reduces the time consumption and improves the efficiency. Moreover, the method will not fail due to the complexity of the distribution network operation mode, and solves the technical problems that the existing zero-state starting strategy of the electromagnetic transient simulation of the distribution network adopts a long time consumption and is easy to fail due to the complexity of the distribution network. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0054] Figure 1A schematic diagram of a flow chart of a method for initializing electromagnetic transient simulation of a distribution network provided in an embodiment of the present invention;

[0055] Figure 2 A three-phase transmission line model provided in an embodiment of the present invention;

[0056] Figure 3 When the capacitor is ignored, Figure 2 The corresponding equivalent circuit;

[0057] Figure 4 When considering capacitors, Figure 2 The corresponding equivalent circuit;

[0058] Figure 5 A partial schematic diagram of the topological structure of the IEEE37 node system provided in an embodiment of the present invention;

[0059] Figure 6 Another partial schematic diagram of the topological structure of the IEEE37 node system provided in an embodiment of the present invention;

[0060] Figure 7 A schematic diagram of a 730 bus three-phase voltage obtained by simulating an IEEE37 node system provided in an embodiment of the present invention;

[0061] Figure 8 A schematic diagram of the effective value of the A-phase voltage obtained by simulating the IEEE37 node system provided in an embodiment of the present invention;

[0062] Fig. 9 It is a simulation curve diagram of active power and reactive power of load connected to bus 742 provided in an embodiment of the present invention;

[0063] Fig.10 The present invention provides a schematic diagram of the structure of a distribution network electromagnetic transient simulation initialization system. DETAILED DESCRIPTION

[0064] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings 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 field without creative work are within the scope of protection of the present invention.

[0065] For easier understanding, see Figure 1 The present invention provides an embodiment of a method for initializing electromagnetic transient simulation of a distribution network, comprising:

[0066] Step 101, building a power distribution network system simulation circuit;

[0067] Step 102, calculating the node admittance matrix of the distribution network system simulation circuit;

[0068] Step 103, calculating the three-phase asymmetric power flow of the distribution network system simulation circuit;

[0069] Step 104: Calculate the historical current of each component according to the node admittance matrix and the three-phase asymmetric power flow to obtain the initialization current of the node to be initialized.

[0070] It should be noted that after the distribution network system simulation circuit is built, the branch admittance matrices of the distribution network transmission lines, transformers, capacitors and other components are solved respectively, and the system node admittance matrix is ​​solved using the branch admittance matrix of each component. The specific branch admittance matrix and node admittance matrix process are existing technologies and will not be described in detail here. The three-phase power flow equation of the distribution network bus is expressed as:

[0071]

[0072]

[0073] Among them, V i m and is the voltage between node i and node jm, and is the conductance and susceptance between nodes i and j, is the phase angle difference between node i and node j, P i m and is the active power and reactive power injected into the node im phase,

[0074] Using the Newton-Raphson method to solve the above equation, we can get the following deviation equation:

[0075]

[0076] in, and is the deviation between active power and reactive power of phase C at node n, and is the deviation of the phase angle and voltage of node n C, and H, N, J and L are the elements of the Jacobian matrix.

[0077] The solution of the Jacobian matrix elements can be obtained as follows:

[0078]

[0079] The formula for updating the phase voltage and phase angle is:

[0080]

[0081] in, is the phase angle of the m-phase (m=a,b,c) at the k+1 iteration node, is the voltage amplitude of phase m (m=a, b, c) at the k+1 iteration node.

[0082] When calculating three-phase asymmetric power flow:

[0083] First, initialize the voltage and phase angle of each phase of the system node;

[0084] Then, the active deviation and reactive deviation injected into each phase of the node are calculated using formula (1) (the initial value is 0, so the calculation result in formula (1) is the deviation);

[0085] Formula (2) can be used to calculate the voltage deviation and phase angle deviation of each phase of the node;

[0086] The voltage and phase angle of each phase of the node are updated using equation (4). When the iteration is repeated until convergence, the voltage and phase angle of each phase obtained are the final voltage and phase angle of each phase.

[0087] According to the calculation results of the three-phase asymmetric power flow and the node voltage equation I=YV (I is the current parameter, Y is the admittance parameter, and V is the voltage parameter), the historical current of each component can be obtained, thereby determining the initialization current of the node to be initialized.

[0088] The distribution network electromagnetic transient simulation initialization method provided in the embodiment of the present invention uses a startup strategy based on three-phase asymmetric power flow calculation, and uses the three-phase asymmetric power flow calculation results for initialization, so that the system can quickly reach a stable state and can run to a stable state in about 0.6s. Compared with the existing zero-state startup strategy, a system of the same size requires 6-8s, which greatly reduces the time consumption and improves the efficiency. It will not fail due to the complexity of the distribution network operation mode, and solves the technical problems that the existing distribution network electromagnetic transient simulation adopts a zero-state startup strategy, which is time-consuming and easy to fail due to the complexity of the distribution network.

[0089] In one embodiment, the calculation formula of the historical current of each component is:

[0090] I history (t-Δt)=m·V(t-Δt)+n·I(t-Δt)

[0091] Wherein, m is the voltage coefficient, n is the current coefficient, V(t-Δt) is the branch voltage for power flow calculation, and I(t-Δt) is the branch current for power flow calculation.

[0092] The electromagnetic transient simulation equation of transmission line k can be written as:

[0093] i km (t) = G[V k (t)-V m (t)]+I history (t-Δt)

[0094] I history (t-Δt)=P·V(t-Δt)+Q·I(t-Δt)

[0095] Among them, i km (t) is the m-phase branch current of transmission line k at time t, G is the node admittance matrix of transmission line k, V k (t) is the voltage at one end of the transmission line, V m (t) is the voltage at the other end of the transmission line.

[0096] For the distribution network, the transmission lines, transformers, loads, capacitors and other components in the network are modeled by using differentiation, and each component is expressed as a Norton equivalent circuit. Then the network is numbered, and the node voltage method can be used to write the node voltage equation of the network and form a network solution equation. The Norton equivalent current (i.e., the historical current term) at the next moment is calculated by the voltage and current vectors of each branch, and the network solution equation is updated, and the cycle continues until the simulation time ends.

[0097] Taking a three-phase transmission line as an example, the three-phase transmission line model is as follows: Figure 2 As shown. Order:

[0098]

[0099]

[0100] When the capacitor is ignored, the distribution network transmission line satisfies the following equation:

[0101]

[0102] Among them, I RL is the current at both ends of the line. Integrate the left and right sides from t-Δt to t and sort them out to get:

[0103] I RL (t) = [R*Δt+2L] -1 *ΔV(t)*Δt+[R*Δt+2L] -1 *ΔV(t-Δt)*Δt+[R*Δt+2L] -1 *[2L-R*Δt]*[I RL (t-Δt)]

[0104] make Reff is the Norton equivalent resistance of the Norton equivalent circuit.

[0105] but,

[0106] I history =[R*Δt+2L] -1 *ΔV(t-Δt)*Δt+[R*Δt+2L] -1 *[2L-R*Δt]*[I RL (t-Δt)]

[0107] Wherein, R is the equivalent resistance of the Norton equivalent circuit, L is the equivalent inductance of the Norton equivalent circuit, and ΔV is the branch voltage for power flow calculation.

[0108] Therefore, ignoring the capacitor, Figure 2 The corresponding equivalent circuit is Figure 3 shown.

[0109] When considering the effect of capacitors, let:

[0110]

[0111] Among them, the current flowing to the capacitor on the ABC side and the abc side is recorded as:

[0112]

[0113] satisfy:

[0114] Integrate both sides of the above equation from t-Δt to t and sort them out to get:

[0115]

[0116] make: R eff - 1 is the Norton equivalent conductance of the capacitor Norton equivalent circuit.

[0117] but,

[0118] I CABC (t) = R eff -1 ·V ABC (t)+I history(t-Δt)

[0119]

[0120] Therefore, when considering the effect of capacitors, Figure 2 The corresponding equivalent circuit is Figure 4 shown.

[0121] In order to more intuitively verify and illustrate the distribution network electromagnetic transient simulation initialization method provided in the embodiment of the present invention, the present invention adopts the IEEE37 node system for testing. The topology structure of the IEEE37 node system is as follows: Figure 5 and Figure 6 shown.

[0122] This topology has one three-phase voltage source, three transformers, 36 distribution network transmission lines, and 12 loads, among which the loads connected to busbars 701 and 742 are distributed power sources. Three-phase asymmetric power flow simulation and electromagnetic transient simulation are performed on this example, and the electromagnetic transient simulation startup strategy adopts the startup strategy based on three-phase asymmetric power flow calculation proposed in the present invention.

[0123] The system is simulated for three-phase asymmetric power flow. The partial power flow calculation results of this example are shown in Table 1:

[0124] Table 1 Partial power flow calculation results of IEEE37 node example

[0125]

[0126] The simulated 730 bus three-phase voltage is as follows Figure 7 As shown, the effective value of phase A voltage is as follows Figure 8 As shown. Figure 7 to Figure 8 It can be seen that the startup strategy based on three-phase asymmetric power flow calculation proposed in the present invention is very effective. The system quickly reaches a stable state using the three-phase asymmetric power flow calculation results, and the effective value of the voltage of the bus 730 is basically consistent with the power flow calculation results.

[0127] The simulation curves of active power and reactive power of the load connected to the 742 bus are as follows: Fig. 9 As shown, from Fig. 9 It can be seen that after the initialization process of the power flow section of the entire system, the system quickly and smoothly reaches a steady state, the active power and reactive power of the load connected to the 742 bus tend to be stable and are basically consistent with the power flow calculation results, and the entire system runs to a stable state in about 0.6s.

[0128] For easier understanding, see Fig.10 The present invention provides an embodiment of a distribution network electromagnetic transient simulation initialization system, comprising:

[0129] A simulation circuit construction module 201 is used to construct a distribution network system simulation circuit;

[0130] A node admittance calculation module 202 is used to calculate the node admittance matrix of the power distribution network system simulation circuit;

[0131] A three-phase asymmetric power flow calculation module 203, used to calculate the three-phase asymmetric power flow of the power distribution network system simulation circuit;

[0132] The historical current calculation module 204 is used to calculate the historical current of each component according to the node admittance matrix and the three-phase asymmetric power flow to obtain the initialization current of the node to be initialized.

[0133] The node admittance calculation module 202 is specifically used for:

[0134] Solve the branch admittance matrix of each component of the distribution network system simulation circuit;

[0135] The node admittance matrix is ​​solved according to the branch admittance matrix of each element.

[0136] The three-phase asymmetric power flow calculation module 203 is specifically used for:

[0137] Initializing each phase voltage and phase angle of the power distribution network system simulation circuit;

[0138] Calculate the active deviation and reactive deviation injected into each phase of the node;

[0139] Calculate the voltage deviation and phase angle deviation of each phase of the node according to the active deviation and reactive deviation;

[0140] Update the voltage and phase angle of each phase according to the voltage deviation and phase angle deviation of each phase;

[0141] Output the updated phase voltage and phase angle when the iteration converges.

[0142] The calculation formula for the historical current of each component is:

[0143] I history (t-Δt)=m·V(t-Δt)+n·I(t-Δt)

[0144] Wherein, m is the voltage coefficient, n is the current coefficient, V(t-Δt) is the branch voltage for power flow calculation, and I(t-Δt) is the branch current for power flow calculation.

[0145] When the effect of the capacitor is taken into account, the calculation formula for the historical current of the capacitor is:

[0146]

[0147] Where C is the equivalent capacitance of the Norton equivalent circuit,

[0148] When the effect of the capacitor is not considered, the calculation formula for the historical current of the transmission line is:

[0149] I history =[R*Δt+2L] -1 *ΔV(t-Δt)*Δt+[R*Δt+2L] -1*[2L-R*Δt]*[I RL (t-Δt)]

[0150] Where R is the equivalent resistance of the Norton equivalent circuit, L is the equivalent inductance of the Norton equivalent circuit, ΔV is the branch voltage for power flow calculation, and I RL is the current at both ends of the line.

[0151] The distribution network electromagnetic transient simulation initialization system provided in the embodiment of the present invention adopts a startup strategy based on three-phase asymmetric power flow calculation, and uses the three-phase asymmetric power flow calculation results for initialization, so that the system can quickly reach a stable state and can run to a stable state in about 0.6s. Compared with the existing zero-state startup strategy, a system of the same size requires 6-8s, which greatly reduces the time consumption and improves the efficiency. It will not fail due to the complexity of the distribution network operation mode, and solves the technical problems that the existing distribution network electromagnetic transient simulation adopts a zero-state startup strategy, which is time-consuming and easy to fail due to the complexity of the distribution network.

[0152] As described above, the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features thereof may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for initializing electromagnetic transient simulation of a distribution network, characterized in that: include: Build a simulation circuit for the distribution network system; Calculating a node admittance matrix of the power distribution network system simulation circuit; Calculating the three-phase asymmetric power flow of the power distribution network system simulation circuit; Calculating the historical current of each component according to the node admittance matrix and the three-phase asymmetric power flow to obtain the initialization current of the node to be initialized; Calculating the three-phase asymmetric power flow of the power distribution network system simulation circuit, including: Initializing each phase voltage and phase angle of the power distribution network system simulation circuit; Calculate the active deviation and reactive deviation injected into each phase of the node; Calculate the voltage deviation and phase angle deviation of each phase of the node according to the active deviation and reactive deviation; Update the voltage and phase angle of each phase according to the voltage deviation and phase angle deviation of each phase; Output the updated phase voltage and phase angle when the iteration converges; The calculation formula for the historical current of each component is: I history (t-Δt)=m·V(t-Δt)+n·I(t-Δt) Among them, I history (t-Δt) is the historical current of the component, m is the voltage coefficient, n is the current coefficient, V(t-Δt) is the branch voltage for power flow calculation, and I(t-Δt) is the branch current for power flow calculation; When the effect of the capacitor is taken into account, the calculation formula for the historical current of the capacitor is: Among them, I Chistory(t-Δt) To consider the historical current of the capacitor when the capacitor is affected, C is the equivalent capacitance of the Norton equivalent circuit, When the effect of the capacitor is not considered, the calculation formula for the historical current of the transmission line is: I RLhistory =[R*Δt+2L] -1 *ΔV(t-Δt)*Δt+[R*Δt+2L] -1 *[2L-R*Δt]*[I RL (t-Δt)] Among them, I RLhistory is the historical current of the transmission line without considering the influence of the capacitor, R is the equivalent resistance of the Norton equivalent circuit, L is the equivalent inductance of the Norton equivalent circuit, ΔV is the branch voltage of the power flow calculation, I RL is the current at both ends of the line.

2. The method for initializing the electromagnetic transient simulation of the distribution network according to claim 1, characterized in that: Calculating the node admittance matrix of the power distribution network system simulation circuit includes: Solve the branch admittance matrix of each component of the distribution network system simulation circuit; The node admittance matrix is ​​solved according to the branch admittance matrix of each element.

3. A distribution network electromagnetic transient simulation initialization system, characterized in that: include: Simulation circuit construction module, used to build distribution network system simulation circuit; A node admittance calculation module, used to calculate the node admittance matrix of the power distribution network system simulation circuit; A three-phase asymmetric power flow calculation module, used to calculate the three-phase asymmetric power flow of the distribution network system simulation circuit; A historical current calculation module, used to calculate the historical current of each component according to the node admittance matrix and the three-phase asymmetric power flow, and obtain the initialization current of the node to be initialized; Calculating the three-phase asymmetric power flow of the power distribution network system simulation circuit, including: Initializing each phase voltage and phase angle of the power distribution network system simulation circuit; Calculate the active deviation and reactive deviation injected into each phase of the node; Calculate the voltage deviation and phase angle deviation of each phase of the node according to the active deviation and reactive deviation; Update the voltage and phase angle of each phase according to the voltage deviation and phase angle deviation of each phase; Output the updated phase voltage and phase angle when the iteration converges; The calculation formula for the historical current of each component is: I history (t-Δt)=m·V(t-Δt)+n·I(t-Δt) Among them, I history (t-Δt) is the historical current of the component, m is the voltage coefficient, n is the current coefficient, V(t-Δt) is the branch voltage for power flow calculation, and I(t-Δt) is the branch current for power flow calculation; When the effect of the capacitor is taken into account, the calculation formula for the historical current of the capacitor is: Among them, I Chistory(t-Δt) To consider the historical current of the capacitor when the capacitor is affected, C is the equivalent capacitance of the Norton equivalent circuit, When the effect of the capacitor is not considered, the calculation formula for the historical current of the transmission line is: I RLhistory =[R*Δt+2L] -1 *ΔV(t-Δt)*Δt+[R*Δt+2L] -1 *[2L-R*Δt]*[I RL (t-Δt)] Among them, I RLhistory is the historical current of the transmission line without considering the influence of the capacitor, R is the equivalent resistance of the Norton equivalent circuit, L is the equivalent inductance of the Norton equivalent circuit, ΔV is the branch voltage of the power flow calculation, I RL is the current at both ends of the line.

4. The distribution network electromagnetic transient simulation initialization system according to claim 3, characterized in that: The node admittance calculation module is specifically used for: Solve the branch admittance matrix of each component of the distribution network system simulation circuit; The node admittance matrix is ​​solved according to the branch admittance matrix of each element.

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